The-OpenROAD-Project_OpenSTA/dcalc/GraphDelayCalc.cc

// OpenSTA, Static Timing Analyzer
// Copyright (c) 2026, Parallax Software, Inc.
// 
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// 
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// 
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
// 
// The origin of this software must not be misrepresented; you must not
// claim that you wrote the original software.
// 
// Altered source versions must be plainly marked as such, and must not be
// misrepresented as being the original software.
// 
// This notice may not be removed or altered from any source distribution.

#include "GraphDelayCalc.hh"

#include <array>
#include <cmath>
#include <set>
#include <string_view>

#include "ArcDelayCalc.hh"
#include "Bfs.hh"
#include "ClkNetwork.hh"
#include "ContainerHelpers.hh"
#include "Debug.hh"
#include "Graph.hh"
#include "InputDrive.hh"
#include "Liberty.hh"
#include "MinMax.hh"
#include "Mode.hh"
#include "Mutex.hh"
#include "NetCaps.hh"
#include "Network.hh"
#include "Parasitics.hh"
#include "PortDirection.hh"
#include "Sdc.hh"
#include "Scene.hh"
#include "SearchPred.hh"
#include "search/Sim.hh"
#include "Stats.hh"
#include "TimingArc.hh"
#include "TimingRole.hh"
#include "Variables.hh"
#include "search/Latches.hh"
#include "search/Levelize.hh"

namespace sta {

static const Slew default_slew = 0.0;

static bool
isLeafDriver(const Pin *pin,
	     const Network *network);

////////////////////////////////////////////////////////////////

class DcalcPred : public SearchPred
{
public:
  DcalcPred(const StaState *sta);
  bool searchFrom(const Vertex *from_vertex,
                  const Mode *mode) const override;
  bool searchThru(Edge *edge,
                  const Mode *mode) const override;
  bool searchTo(const Vertex *to_vertex,
                const Mode *mode) const override;
};

DcalcPred::DcalcPred(const StaState *sta) :
  SearchPred(sta)
{
}

bool
DcalcPred::searchFrom(const Vertex *from_vertex,
                      const Mode *mode) const
{
  const Pin *from_pin = from_vertex->pin();
  const Sdc *sdc = mode->sdc();
  const Network *network = sta_->network();
  const Sim *sim = mode->sim();
  Net *net = network->net(from_pin);
  return !(sdc->isDisabledConstraint(from_pin)
           || sim->isConstant(from_vertex)
	   || (net && (network->isPower(net)
                       || network->isGround(net))));
}

bool
DcalcPred::searchThru(Edge *edge,
                      const Mode *mode) const
{
  const Sdc *sdc = mode->sdc();
  const Variables *variables = sta_->variables();
  const TimingRole *role = edge->role();
  return !(role->isTimingCheck()
           || (role == TimingRole::regSetClr()
	       && !variables->presetClrArcsEnabled())
           || edge->isDisabledLoop()
           || sdc->isDisabledConstraint(edge)
           || sdc->isDisabledCondDefault(edge)
           || sta_->isDisabledBidirectInstPath(edge));
}

bool
DcalcPred::searchTo(const Vertex *,
                    const Mode *) const
{
  return true;
}

class DcalcNonLatchPred : public DcalcPred
{
public:
  DcalcNonLatchPred(const StaState *sta);
  bool searchThru(Edge *edge,
                  const Mode *mode) const override;
};

DcalcNonLatchPred::DcalcNonLatchPred(const StaState *sta) :
  DcalcPred(sta)
{
}

bool
DcalcNonLatchPred::searchThru(Edge *edge,
                              const Mode *mode) const
{
  return DcalcPred::searchThru(edge, mode)
    && !edge->role()->isLatchDtoQ();
}

////////////////////////////////////////////////////////////////

GraphDelayCalc::GraphDelayCalc(StaState *sta) :
  StaState(sta),
  invalid_delays_(makeVertexSet(this)),
  search_pred_(new DcalcPred(sta)),
  search_non_latch_pred_(new DcalcNonLatchPred(sta)),
  iter_(new BfsFwdIterator(BfsIndex::dcalc, search_non_latch_pred_, sta))
{
}

GraphDelayCalc::~GraphDelayCalc()
{
  delete search_pred_;
  delete search_non_latch_pred_;
  delete iter_;
  deleteMultiDrvrNets();
  delete observer_;
}

void
GraphDelayCalc::deleteMultiDrvrNets()
{
  std::set<MultiDrvrNet*> drvr_nets;
  for (auto [vertex, multi_drvr] : multi_drvr_net_map_) {
    // Multiple drvr pins point to the same drvr PinSet,
    // so collect them into a set.
    drvr_nets.insert(multi_drvr);
  }
  multi_drvr_net_map_.clear();
  deleteContents(drvr_nets);
}

void
GraphDelayCalc::copyState(const StaState *sta)
{
  StaState::copyState(sta);
  // Notify sub-components.
  iter_->copyState(sta);
  search_pred_->copyState(sta);
  search_non_latch_pred_->copyState(sta);
}

void
GraphDelayCalc::clear()
{
  delaysInvalid();
  deleteMultiDrvrNets();
}

float
GraphDelayCalc::incrementalDelayTolerance()
{
  return incremental_delay_tolerance_;
}

void
GraphDelayCalc::setIncrementalDelayTolerance(float tol)
{
  incremental_delay_tolerance_ = tol;
}

void
GraphDelayCalc::setObserver(DelayCalcObserver *observer)
{
  delete observer_;
  observer_ = observer;
}

void
GraphDelayCalc::delaysInvalid()
{
  debugPrint(debug_, "delay_calc", 1, "delays invalid");
  delays_exist_ = false;
  delays_seeded_ = false;
  iter_->clear();
  // No need to keep track of incremental updates any more.
  invalid_delays_.clear();
  invalid_check_edges_.clear();
  invalid_latch_edges_.clear();
}

void
GraphDelayCalc::delayInvalid(const Pin *pin)
{
  if (graph_ && delays_exist_) {
    if (network_->isHierarchical(pin)) {
      EdgesThruHierPinIterator edge_iter(pin, network_, graph_);
      while (edge_iter.hasNext()) {
	Edge *edge = edge_iter.next();
	delayInvalid(edge->from(graph_));
      }
    }
    else {
      Vertex *vertex, *bidirect_drvr_vertex;
      graph_->pinVertices(pin, vertex, bidirect_drvr_vertex);
      if (vertex)
	delayInvalid(vertex);
      if (bidirect_drvr_vertex)
	delayInvalid(bidirect_drvr_vertex);
    }
  }
}

void
GraphDelayCalc::delayInvalid(Vertex *vertex)
{
  debugPrint(debug_, "delay_calc", 2, "delay invalid {}",
             vertex->to_string(this));
  if (delays_exist_) {
    invalid_delays_.insert(vertex);
    // Invalidate driver that triggers dcalc for multi-driver nets.
    MultiDrvrNet *multi_drvr = multiDrvrNet(vertex);
    if (multi_drvr)
      invalid_delays_.insert(multi_drvr->dcalcDrvr());
  }
}

void
GraphDelayCalc::levelsChangedBefore()
{
  delaysInvalid();
}

void
GraphDelayCalc::levelChangedBefore(Vertex *vertex)
{
  iter_->remove(vertex);
  delayInvalid(vertex);
}

void
GraphDelayCalc::deleteVertexBefore(Vertex *vertex)
{
  iter_->deleteVertexBefore(vertex);
  if (delays_exist_)
    invalid_delays_.erase(vertex);
  MultiDrvrNet *multi_drvr = multiDrvrNet(vertex);
  if (multi_drvr) {
    // Don't bother incrementally updating MultiDrvrNet.
    for (Vertex *drvr_vertex : multi_drvr->drvrs())
      multi_drvr_net_map_.erase(drvr_vertex);
    delete multi_drvr;
  }
}

////////////////////////////////////////////////////////////////

class FindVertexDelays : public VertexVisitor
{
public:
  FindVertexDelays(GraphDelayCalc *graph_delay_calc1);
  FindVertexDelays(const FindVertexDelays &find_vertex_delays);
  ~FindVertexDelays() override;
  void visit(Vertex *vertex) override;
  VertexVisitor *copy() const override;

protected:
  GraphDelayCalc *graph_delay_calc_;
  ArcDelayCalc *arc_delay_calc_;
};

FindVertexDelays::FindVertexDelays(GraphDelayCalc *graph_delay_calc) :
  VertexVisitor(),
  graph_delay_calc_(graph_delay_calc),
  arc_delay_calc_(graph_delay_calc_->arc_delay_calc_->copy())
{
}

FindVertexDelays::FindVertexDelays(const FindVertexDelays &find_vertex_delays) :
  FindVertexDelays(find_vertex_delays.graph_delay_calc_)
{
}

FindVertexDelays::~FindVertexDelays()
{
  delete arc_delay_calc_;
}

VertexVisitor *
FindVertexDelays::copy() const
{
  // Copy StaState::arc_delay_calc_ because it needs separate state
  // for each thread.
  return new FindVertexDelays(*this);
}

void
FindVertexDelays::visit(Vertex *vertex)
{
  graph_delay_calc_->findVertexDelay(vertex, arc_delay_calc_);
}

// The logical structure of incremental delay calculation closely
// resembles the incremental search arrival time algorithm
// (Search::findArrivals).
void
GraphDelayCalc::findDelays(Level level)
{
  Stats stats(debug_, report_);
  int dcalc_count = 0;
  debugPrint(debug_, "delay_calc", 1, "find delays to level {}", level);
  if (!delays_seeded_) {
    iter_->clear();
    seedRootSlews();
    delays_seeded_ = true;
  }
  else
    iter_->ensureSize();
  if (delays_exist_)
    seedInvalidDelays();

  if (!iter_->empty()) {
    FindVertexDelays visitor(this);
    dcalc_count += iter_->visitParallel(level, &visitor);
  }

  // Timing checks require slews at both ends of the arc,
  // so find their delays after all slews are known.
  for (Edge *check_edge : invalid_check_edges_)
    findCheckEdgeDelays(check_edge, arc_delay_calc_);
  invalid_check_edges_.clear();

  for (Edge *latch_edge : invalid_latch_edges_)
    findLatchEdgeDelays(latch_edge);
  invalid_latch_edges_.clear();

  delays_exist_ = true;
  debugPrint(debug_, "delay_calc", 1, "found {} delays", dcalc_count);
  stats.report("Delay calc");
}

void
GraphDelayCalc::seedInvalidDelays()
{
  for (Vertex *vertex : invalid_delays_)
    iter_->enqueue(vertex);
  invalid_delays_.clear();
}

void
GraphDelayCalc::seedRootSlews()
{
  for (Vertex *vertex : levelize_->roots())
    seedRootSlew(vertex, arc_delay_calc_);
}

void
GraphDelayCalc::seedRootSlew(Vertex *vertex,
                             ArcDelayCalc *arc_delay_calc)
{
  if (vertex->isDriver(network_))
    seedDrvrSlew(vertex, arc_delay_calc);
  else
    seedLoadSlew(vertex);
  iter_->enqueueFanout(vertex);
}

void
GraphDelayCalc::seedDrvrSlew(Vertex *drvr_vertex,
                             ArcDelayCalc *arc_delay_calc)
{
  const Pin *drvr_pin = drvr_vertex->pin();
  debugPrint(debug_, "delay_calc", 2, "seed driver slew {}",
             drvr_vertex->to_string(this));
  for (const Scene *scene : scenes_) {
    const Sdc *sdc = scene->sdc();
    for (const MinMax *min_max : MinMax::range()) {
      for (const RiseFall *rf : RiseFall::range()) {
        InputDrive *drive = nullptr;
        if (network_->isTopLevelPort(drvr_pin)) {
          Port *port = network_->port(drvr_pin);
          drive = sdc->findInputDrive(port);
        }
        if (drive) {
          const LibertyCell *drvr_cell;
          const LibertyPort *from_port, *to_port;
          const DriveCellSlews *from_slews;
          drive->driveCell(rf, min_max, drvr_cell, from_port,
                           from_slews, to_port);
          if (drvr_cell) {
            if (from_port == nullptr)
              from_port = driveCellDefaultFromPort(drvr_cell, to_port);
            findInputDriverDelay(drvr_cell, drvr_pin, drvr_vertex, rf,
                                 from_port, from_slews, to_port, scene, min_max,
                                 arc_delay_calc);
          }
          else
            seedNoDrvrCellSlew(drvr_vertex, drvr_pin, rf, drive, scene, min_max,
                               arc_delay_calc);
        }
        else
          seedNoDrvrSlew(drvr_vertex, drvr_pin, rf, scene, min_max, arc_delay_calc);
      }
    }
  }
}

void
GraphDelayCalc::seedNoDrvrCellSlew(Vertex *drvr_vertex,
                                   const Pin *drvr_pin,
                                   const RiseFall *rf,
                                   const InputDrive *drive,
                                   const Scene *scene,
                                   const MinMax *min_max,
                                   ArcDelayCalc *arc_delay_calc)
{
  DcalcAPIndex ap_index = scene->dcalcAnalysisPtIndex(min_max);
  Slew slew = default_slew;
  float drive_slew;
  bool exists;
  drive->slew(rf, min_max, drive_slew, exists);
  if (exists)
    slew = drive_slew;
  else {
    // Top level bidirect driver uses load slew unless
    // bidirect instance paths are disabled.
    if (bidirectDrvrSlewFromLoad(drvr_pin)) {
      Vertex *load_vertex = graph_->pinLoadVertex(drvr_pin);
      slew = graph_->slew(load_vertex, rf, ap_index);
    }
  }
  Delay drive_delay = delay_zero;
  float drive_res;
  drive->driveResistance(rf, min_max, drive_res, exists);
  const Parasitic *parasitic;
  float load_cap;
  parasiticLoad(drvr_pin, rf, scene, min_max, nullptr, arc_delay_calc,
                load_cap, parasitic);
  if (exists) {
    drive_delay = load_cap * drive_res;
    slew = load_cap * drive_res;
  }
  if (!drvr_vertex->slewAnnotated(rf, min_max))
    graph_->setSlew(drvr_vertex, rf, ap_index, slew);
  LoadPinIndexMap load_pin_index_map = makeLoadPinIndexMap(drvr_vertex);
  ArcDcalcResult dcalc_result =
    arc_delay_calc->inputPortDelay(drvr_pin, delayAsFloat(slew), rf, parasitic,
                                   load_pin_index_map, scene, min_max);
  annotateLoadDelays(drvr_vertex, rf, dcalc_result, load_pin_index_map, 
                     drive_delay, false, scene, min_max);
  arc_delay_calc->finishDrvrPin();
}

// Delay calculation propagates slews from a bidirect driver
// to the bidirect port and back through the bidirect driver when
// sta_bidirect_inst_paths_enabled_ is true.
bool
GraphDelayCalc::bidirectDrvrSlewFromLoad(const Pin *pin) const
{
  return variables_->bidirectInstPathsEnabled()
    && network_->direction(pin)->isBidirect()
    && network_->isTopLevelPort(pin);
}

void
GraphDelayCalc::seedNoDrvrSlew(Vertex *drvr_vertex,
                               const Pin *drvr_pin,
                               const RiseFall *rf,
                               const Scene *scene,
                               const MinMax *min_max,
                               ArcDelayCalc *arc_delay_calc)
{
  DcalcAPIndex ap_index = scene->dcalcAnalysisPtIndex(min_max);
  Slew slew = default_slew;
  // Top level bidirect driver uses load slew unless
  // bidirect instance paths are disabled.
  if (bidirectDrvrSlewFromLoad(drvr_pin)) {
    Vertex *load_vertex = graph_->pinLoadVertex(drvr_pin);
    slew = graph_->slew(load_vertex, rf, ap_index);
  }
  if (!drvr_vertex->slewAnnotated(rf, min_max))
    graph_->setSlew(drvr_vertex, rf, ap_index, slew);
  Parasitic *parasitic = arc_delay_calc->findParasitic(drvr_pin, rf, scene, min_max);
  LoadPinIndexMap load_pin_index_map = makeLoadPinIndexMap(drvr_vertex);
  ArcDcalcResult dcalc_result =
    arc_delay_calc->inputPortDelay(drvr_pin, delayAsFloat(slew), rf, parasitic,
                                   load_pin_index_map, scene, min_max);
  annotateLoadDelays(drvr_vertex, rf, dcalc_result, load_pin_index_map, delay_zero,
                     false, scene, min_max);
  arc_delay_calc->finishDrvrPin();
}

void
GraphDelayCalc::seedLoadSlew(Vertex *vertex)
{
  const Pin *pin = vertex->pin();
  debugPrint(debug_, "delay_calc", 2, "seed load slew {}",
             vertex->to_string(this));
  initSlew(vertex);
  for (const Scene *scene : scenes_) {
    const Sdc *sdc = scene->sdc();
    for (const MinMax *min_max : MinMax::range()) {
      DcalcAPIndex ap_index = scene->dcalcAnalysisPtIndex(min_max);
      for (const RiseFall *rf : RiseFall::range()) {
        ClockSet *clks = sdc->findLeafPinClocks(pin);
        if (!vertex->slewAnnotated(rf, min_max)) {
          float slew = 0.0;
          if (clks) {
            slew = min_max->initValue();
            for (Clock *clk : *clks) {
              float clk_slew = clk->slew(rf, min_max);
              if (min_max->compare(clk_slew, slew))
                slew = clk_slew;
            }
          }
          graph_->setSlew(vertex, rf, ap_index, slew);
        }
      }
    }
  }
}

// If a driving cell does not specify a -from_pin, the first port
// defined in the cell that has a timing group to the output port
// is used.  Not exactly reasonable, but it's compatible.
LibertyPort *
GraphDelayCalc::driveCellDefaultFromPort(const LibertyCell *cell,
                                         const LibertyPort *to_port)
{
  LibertyPort *from_port = nullptr;
  int from_port_index = 0;
  for (TimingArcSet *arc_set : cell->timingArcSetsTo(to_port)) {
    LibertyPort *set_from_port = arc_set->from();
    int set_from_port_index = findPortIndex(cell, set_from_port);
    if (from_port == nullptr
        || set_from_port_index < from_port_index) {
      from_port = set_from_port;
      from_port_index = set_from_port_index;
    }
  }
  return from_port;
}

// Find the index that port is defined in cell.
int
GraphDelayCalc::findPortIndex(const LibertyCell *cell,
                              const LibertyPort *port)
{
  int index = 0;
  LibertyCellPortIterator port_iter(cell);
  while (port_iter.hasNext()) {
    LibertyPort *cell_port = port_iter.next();
    if (cell_port == port)
      return index;
    index++;
  }
  report_->critical(1100, "port not found in cell.");
  return 0;
}

void
GraphDelayCalc::findInputDriverDelay(const LibertyCell *drvr_cell,
                                     const Pin *drvr_pin,
                                     Vertex *drvr_vertex,
                                     const RiseFall *rf,
                                     const LibertyPort *from_port,
                                     const DriveCellSlews *from_slews,
                                     const LibertyPort *to_port,
                                     const Scene *scene,
                                     const MinMax *min_max,
                                     ArcDelayCalc *arc_delay_calc)
{
  debugPrint(debug_, "delay_calc", 2, "  driver cell {} {}",
             drvr_cell->name(),
             rf->shortName());
  for (TimingArcSet *arc_set : drvr_cell->timingArcSets(from_port, to_port)) {
    for (TimingArc *arc : arc_set->arcs()) {
      if (arc->toEdge()->asRiseFall() == rf) {
        float from_slew = (*from_slews)[arc->fromEdge()->index()];
        findInputArcDelay(drvr_pin, drvr_vertex, arc, from_slew, scene, min_max,
                          arc_delay_calc);
      }
    }
  }
}

// Driving cell delay is the load dependent delay, which is the gate
// delay minus the intrinsic delay.  Driving cell delays are annotated
// to the wire arcs from the input port pin to the load pins.
void
GraphDelayCalc::findInputArcDelay(const Pin *drvr_pin,
                                  Vertex *drvr_vertex,
                                  const TimingArc *arc,
                                  float from_slew,
                                  const Scene *scene,
                                  const MinMax *min_max,
                                  ArcDelayCalc *arc_delay_calc)
{
  debugPrint(debug_, "delay_calc", 3, "  {} {} -> {} {} ({})",
             arc->from()->name(),
             arc->fromEdge()->to_string(),
             arc->to()->name(),
             arc->toEdge()->to_string(),
             arc->role()->to_string());
  const RiseFall *drvr_rf = arc->toEdge()->asRiseFall();
  if (drvr_rf) {
    DcalcAPIndex ap_index = scene->dcalcAnalysisPtIndex(min_max);

    const Parasitic *parasitic;
    float load_cap;
    parasiticLoad(drvr_pin, drvr_rf, scene, min_max, nullptr, arc_delay_calc,
                  load_cap, parasitic);

    LoadPinIndexMap load_pin_index_map = makeLoadPinIndexMap(drvr_vertex);
    ArcDcalcResult intrinsic_result =
      arc_delay_calc->gateDelay(drvr_pin, arc, from_slew, 0.0, nullptr,
                                load_pin_index_map, scene, min_max);
    const ArcDelay &intrinsic_delay = intrinsic_result.gateDelay();

    ArcDcalcResult gate_result = arc_delay_calc->gateDelay(drvr_pin, arc,
                                                           from_slew, load_cap,
                                                           parasitic, 
                                                           load_pin_index_map,
                                                           scene, min_max);
    const ArcDelay &gate_delay = gate_result.gateDelay();
    const Slew &gate_slew = gate_result.drvrSlew();

    const ArcDelay load_delay = delayDiff(gate_delay, intrinsic_delay, this);
    debugPrint(debug_, "delay_calc", 3,
               "    gate delay = {} intrinsic = {} slew = {}",
               delayAsString(gate_delay, this),
               delayAsString(intrinsic_delay, this),
               delayAsString(gate_slew, this));
    graph_->setSlew(drvr_vertex, drvr_rf, ap_index, gate_slew);
    annotateLoadDelays(drvr_vertex, drvr_rf, gate_result, load_pin_index_map, 
                       load_delay, false, scene, min_max);
    arc_delay_calc->finishDrvrPin();
  }
}

void
GraphDelayCalc::findDelays(Vertex *drvr_vertex)
{
  findVertexDelay(drvr_vertex, arc_delay_calc_);
}

void
GraphDelayCalc::findVertexDelay(Vertex *vertex,
                                ArcDelayCalc *arc_delay_calc)
{
  const Pin *pin = vertex->pin();
  debugPrint(debug_, "delay_calc", 2, "find delays {} ({})",
             vertex->to_string(this),
             network_->cellName(network_->instance(pin)));
  if (vertex->isRoot()
      // Bidirect port drivers are enqueued by their load vertex in
      // annotateLoadDelays.
      || (vertex->isBidirectDriver()
          && network_->isTopLevelPort(pin)))
    seedRootSlew(vertex, arc_delay_calc);
  else if (network_->isLeaf(pin)
           && vertex->isDriver(network_)) {
    LoadPinIndexMap load_pin_index_map = makeLoadPinIndexMap(vertex);
    DrvrLoadSlews load_slews_prev;
    if (delays_exist_)
      load_slews_prev = loadSlews(load_pin_index_map);
    findDriverDelays(vertex, arc_delay_calc, load_pin_index_map);
    if (network_->direction(pin)->isInternal())
      enqueueCheckEdges(vertex);
    graph_->visitFanouts(vertex, search_non_latch_pred_,
                         [this, &load_slews_prev, &load_pin_index_map]
                         (Vertex *fanout) {
                           // Enqueue adjacent vertices even if the load slew
                           // did not change when non-incremental to stride
                           // past annotations.
                           if (!delays_exist_
                               || loadSlewChanged(fanout, load_slews_prev,
                                                  load_pin_index_map)) {
                             iter_->enqueue(fanout);
                             fanout->setBfsPredecessorChanged(true);
                           }
                         });
  }
  else if (vertex->isLoad(network_)) {
    // Load vertex.
    // Includes top level bidirect load vertex with wire edge to bidirect driver.
    enqueueCheckEdges(vertex);
    graph_->visitFanouts(vertex, search_non_latch_pred_,
                         [this] (Vertex *fanout) {
                           iter_->enqueue(fanout);
                           fanout->setBfsPredecessorChanged(true);
                         });
  }
}

DrvrLoadSlews
GraphDelayCalc::loadSlews(LoadPinIndexMap &load_pin_index_map)
{
  size_t slew_count = graph_->slewCount();
  DrvrLoadSlews load_slews(load_pin_index_map.size());
  for (auto const [pin, index] : load_pin_index_map) {
    Vertex *load_vertex = graph_->pinLoadVertex(pin);
    SlewSeq &slews = load_slews[index];;
    slews.resize(slew_count);
    for (size_t i = 0; i < slew_count; i++)
      slews[i] = graph_->slew(load_vertex, i);
  }
  return load_slews;
}

bool
GraphDelayCalc::loadSlewChanged(Vertex *load_vertex,
                                DrvrLoadSlews &load_slews_prev,
                                LoadPinIndexMap &load_pin_index_map)
{
  if (load_slews_prev.empty())
    return true;
  size_t index = load_pin_index_map[load_vertex->pin()];
  SlewSeq &slews_prev = load_slews_prev[index];;
  size_t slew_count = graph_->slewCount();
  for (size_t i = 0; i < slew_count; i++) {
    const Slew slew = graph_->slew(load_vertex, i);
    if (!delayEqual(slew, slews_prev[i], this))
      return true;
  }
  return false;
}

void
GraphDelayCalc::enqueueCheckEdges(Vertex *vertex)
{
  if (vertex->hasChecks()) {
    VertexInEdgeIterator edge_iter(vertex, graph_);
    LockGuard lock(invalid_edge_lock_);
    while (edge_iter.hasNext()) {
      Edge *edge = edge_iter.next();
      if (edge->role()->isTimingCheck())
        invalid_check_edges_.insert(edge);
    }
  }
  if (vertex->isCheckClk()) {
    VertexOutEdgeIterator edge_iter(vertex, graph_);
    LockGuard lock(invalid_edge_lock_);
    while (edge_iter.hasNext()) {
      Edge *edge = edge_iter.next();
      if (edge->role()->isTimingCheck())
        invalid_check_edges_.insert(edge);
    }
  }
  if (network_->isLatchData(vertex->pin())) {
    // Latch D->Q arcs have to be re-evaled if level(D) > level(E)
    // because levelization does not traverse D->Q arcs to break loops.
    VertexOutEdgeIterator edge_iter(vertex, graph_);
    LockGuard lock(invalid_edge_lock_);
    while (edge_iter.hasNext()) {
      Edge *edge = edge_iter.next();
      if (edge->role() == TimingRole::latchDtoQ())
        invalid_latch_edges_.insert(edge);
    }
  }
}

void
GraphDelayCalc::findDriverDelays(Vertex *drvr_vertex,
                                 ArcDelayCalc *arc_delay_calc,
                                 LoadPinIndexMap &load_pin_index_map)
{
  MultiDrvrNet *multi_drvr = findMultiDrvrNet(drvr_vertex);
  if (multi_drvr == nullptr) {
    initLoadSlews(drvr_vertex);
    findDriverDelays1(drvr_vertex, multi_drvr, arc_delay_calc, load_pin_index_map);
  }
  else if (drvr_vertex == multi_drvr->dcalcDrvr()) {
    initLoadSlews(drvr_vertex);
    for (Vertex *drvr : multi_drvr->drvrs())
      findDriverDelays1(drvr, multi_drvr, arc_delay_calc, load_pin_index_map);
  }
  arc_delay_calc->finishDrvrPin();
}

MultiDrvrNet *
GraphDelayCalc::findMultiDrvrNet(Vertex *drvr_vertex)
{
  // Avoid locking for single driver nets.
  if (hasMultiDrvrs(drvr_vertex)) {
    LockGuard lock(multi_drvr_lock_);
    MultiDrvrNet *multi_drvr = multiDrvrNet(drvr_vertex);
    if (multi_drvr)
      return multi_drvr;
    multi_drvr = makeMultiDrvrNet(drvr_vertex);
    return multi_drvr;
  }
  return nullptr;
}

bool
GraphDelayCalc::hasMultiDrvrs(Vertex *drvr_vertex)
{
  Vertex *load_vertex = firstLoad(drvr_vertex);
  if (load_vertex) {
    int drvr_count = 0;
    VertexInEdgeIterator edge_iter(load_vertex, graph_);
    while (edge_iter.hasNext()) {
      Edge *edge = edge_iter.next();
      if (edge->isWire()) {
        Vertex *drvr = edge->from(graph_);
        if (isLeafDriver(drvr->pin(), network_))
          drvr_count++;
      }
      if (drvr_count > 1)
        return true;
    }
    return false;
  }
  return false;
}

Vertex *
GraphDelayCalc::firstLoad(Vertex *drvr_vertex)
{
  VertexOutEdgeIterator edge_iter(drvr_vertex, graph_);
  while (edge_iter.hasNext()) {
    Edge *wire_edge = edge_iter.next();
    if (wire_edge->isWire())
      return wire_edge->to(graph_);
  }
  return nullptr;
}

static bool
isLeafDriver(const Pin *pin,
	     const Network *network)
{
  PortDirection *dir = network->direction(pin);
  const Instance *inst = network->instance(pin);
  return network->isLeaf(inst) && dir->isAnyOutput();
}

MultiDrvrNet *
GraphDelayCalc::multiDrvrNet(const Vertex *drvr_vertex) const
{
  return findKey(multi_drvr_net_map_, drvr_vertex);
}

MultiDrvrNet *
GraphDelayCalc::makeMultiDrvrNet(Vertex *drvr_vertex)
{
  Vertex *load_vertex = firstLoad(drvr_vertex);
  if (load_vertex) {
    debugPrint(debug_, "delay_calc", 3, "multi-driver net");
    MultiDrvrNet *multi_drvr = new MultiDrvrNet;
    VertexSeq &drvr_vertices = multi_drvr->drvrs();
    Level max_drvr_level = 0;
    Vertex *max_drvr = nullptr;
    VertexInEdgeIterator edge_iter(load_vertex, graph_);
    while (edge_iter.hasNext()) {
      Edge *edge = edge_iter.next();
      if (edge->isWire()) {
        Vertex *drvr = edge->from(graph_);
        const Pin *drvr_pin = drvr->pin();
        if (isLeafDriver(drvr_pin, network_)) {
          debugPrint(debug_, "delay_calc", 3, " {}",
                     network_->pathName(drvr_pin));
          multi_drvr_net_map_[drvr] = multi_drvr;
          drvr_vertices.push_back(drvr);
          Level drvr_level = drvr->level();
          if (max_drvr == nullptr
              || drvr_level > max_drvr_level) {
            max_drvr = drvr;
            max_drvr_level = drvr_level;
          }
        }
      }
    }
    multi_drvr->setDcalcDrvr(max_drvr);
    multi_drvr->findCaps(this);
    return multi_drvr;
  }
  report_->critical(1101, "mult_drvr missing load.");
  return nullptr;
}

void
GraphDelayCalc::initLoadSlews(Vertex *drvr_vertex)
{
  VertexOutEdgeIterator edge_iter(drvr_vertex, graph_);
  while (edge_iter.hasNext()) {
    Edge *wire_edge = edge_iter.next();
    if (wire_edge->isWire()) {
      Vertex *load_vertex = wire_edge->to(graph_);
      for (Scene *scene : scenes_) {
        for (const MinMax *min_max : MinMax::range()) {
          DcalcAPIndex ap_index = scene->dcalcAnalysisPtIndex(min_max);
          Slew slew_init_value(min_max->initValue());
          for (const RiseFall *rf : RiseFall::range()) {
            if (!load_vertex->slewAnnotated(rf, min_max))
              graph_->setSlew(load_vertex, rf, ap_index, slew_init_value);
          }
        }
      }
    }
  }
}

bool
GraphDelayCalc::findDriverDelays1(Vertex *drvr_vertex,
                                  MultiDrvrNet *multi_drvr,
                                  ArcDelayCalc *arc_delay_calc,
                                  LoadPinIndexMap &load_pin_index_map)
{
  initSlew(drvr_vertex);
  initWireDelays(drvr_vertex);
  bool delay_changed = false;
  std::array<bool, RiseFall::index_count> delay_exists = {false, false};
  VertexInEdgeIterator edge_iter(drvr_vertex, graph_);
  while (edge_iter.hasNext()) {
    Edge *edge = edge_iter.next();
    if (!edge->role()->isLatchDtoQ())
      delay_changed |= findDriverEdgeDelays(drvr_vertex, multi_drvr, edge,
                                            arc_delay_calc, load_pin_index_map,
                                            delay_exists);
  }
  for (const RiseFall *rf : RiseFall::range()) {
    if (!delay_exists[rf->index()])
      zeroSlewAndWireDelays(drvr_vertex, rf);
  }
  if (delay_changed && observer_)
    observer_->delayChangedTo(drvr_vertex);
  return delay_changed;
}

// Init slews to zero on root vertices that are not inputs, such as
// floating input pins.
void
GraphDelayCalc::initRootSlews(Vertex *vertex)
{
  for (Scene *scene : scenes_) {
    for (const MinMax *min_max : MinMax::range()) {
      DcalcAPIndex ap_index = scene->dcalcAnalysisPtIndex(min_max);
      for (const RiseFall *rf : RiseFall::range()) {
        if (!vertex->slewAnnotated(rf, min_max))
          graph_->setSlew(vertex, rf, ap_index, default_slew);
      }
    }
  }
}

void
GraphDelayCalc::findLatchEdgeDelays(Edge *edge)
{
  Vertex *drvr_vertex = edge->to(graph_);
  const Pin *drvr_pin = drvr_vertex->pin();
  Instance *drvr_inst = network_->instance(drvr_pin);
  debugPrint(debug_, "delay_calc", 2, "find latch D->Q {}",
             sdc_network_->pathName(drvr_inst));
  std::array<bool, RiseFall::index_count> delay_exists = {false, false};
  LoadPinIndexMap load_pin_index_map = makeLoadPinIndexMap(drvr_vertex);
  bool delay_changed = findDriverEdgeDelays(drvr_vertex, nullptr, edge,
                                            arc_delay_calc_, load_pin_index_map,
                                            delay_exists);
  if (delay_changed && observer_)
    observer_->delayChangedTo(drvr_vertex);
}

bool
GraphDelayCalc::findDriverEdgeDelays(Vertex *drvr_vertex,
                                     const MultiDrvrNet *multi_drvr,
                                     Edge *edge,
                                     ArcDelayCalc *arc_delay_calc,
                                     LoadPinIndexMap &load_pin_index_map,
                                     // Return value.
                                     std::array<bool, RiseFall::index_count> &delay_exists)
{
  Vertex *from_vertex = edge->from(graph_);
  const TimingArcSet *arc_set = edge->timingArcSet();
  bool delay_changed = false;

  for (Scene *scene : scenes_) {
    const Mode *mode = scene->mode();
    if (search_pred_->searchFrom(from_vertex, mode)
        && search_pred_->searchThru(edge, mode)) {
      for (const MinMax *min_max : MinMax::range()) {
        for (const TimingArc *arc : arc_set->arcs()) {
          delay_changed |= findDriverArcDelays(drvr_vertex, multi_drvr, edge, arc,
                                               scene, min_max, arc_delay_calc,
                                               load_pin_index_map);
          delay_exists[arc->toEdge()->asRiseFall()->index()] = true;
        }
      }
    }
  }
  if (delay_changed && observer_) {
    observer_->delayChangedFrom(from_vertex);
    observer_->delayChangedFrom(drvr_vertex);
  }
  return delay_changed;
}

// External API.
void
GraphDelayCalc::findDriverArcDelays(Vertex *drvr_vertex,
                                    Edge *edge,
                                    const TimingArc *arc,
                                    const Scene *scene,
                                    const MinMax *min_max,
                                    ArcDelayCalc *arc_delay_calc)
{
  MultiDrvrNet *multi_drvr = multiDrvrNet(drvr_vertex);
  LoadPinIndexMap load_pin_index_map = makeLoadPinIndexMap(drvr_vertex);
  findDriverArcDelays(drvr_vertex, multi_drvr, edge, arc, scene, min_max,
                      arc_delay_calc, load_pin_index_map);
}

bool
GraphDelayCalc::findDriverArcDelays(Vertex *drvr_vertex,
                                    const MultiDrvrNet *multi_drvr,
                                    Edge *edge,
                                    const TimingArc *arc,
                                    const Scene *scene,
                                    const MinMax *min_max,
                                    ArcDelayCalc *arc_delay_calc,
                                    LoadPinIndexMap &load_pin_index_map)
{
  bool delay_changed = false;
  const RiseFall *from_rf = arc->fromEdge()->asRiseFall();
  const RiseFall *drvr_rf = arc->toEdge()->asRiseFall();
  if (from_rf && drvr_rf) {
    const Pin *drvr_pin = drvr_vertex->pin();
    const Parasitic *parasitic;
    float load_cap;
    parasiticLoad(drvr_pin, drvr_rf, scene, min_max, multi_drvr, arc_delay_calc,
                  load_cap, parasitic);

    if (multi_drvr
        && multi_drvr->parallelGates(network_)) {
      ArcDcalcArgSeq dcalc_args = makeArcDcalcArgs(drvr_vertex, multi_drvr,
                                                   edge, arc, scene, min_max,
                                                   arc_delay_calc);
      ArcDcalcResultSeq dcalc_results =
        arc_delay_calc->gateDelays(dcalc_args, load_pin_index_map, scene, min_max);
      for (size_t drvr_idx = 0; drvr_idx < dcalc_args.size(); drvr_idx++) {
        ArcDcalcArg &dcalc_arg = dcalc_args[drvr_idx];
        ArcDcalcResult &dcalc_result = dcalc_results[drvr_idx];
        delay_changed |= annotateDelaysSlews(dcalc_arg.edge(), dcalc_arg.arc(),
                                             dcalc_result, load_pin_index_map,
                                             scene, min_max);
      }
    }
    else {
      Vertex *from_vertex = edge->from(graph_);
      const Slew in_slew = edgeFromSlew(from_vertex, from_rf, edge, scene, min_max);
      ArcDcalcResult dcalc_result = arc_delay_calc->gateDelay(drvr_pin, arc, in_slew,
                                                              load_cap, parasitic,
                                                              load_pin_index_map,
                                                              scene, min_max);
      delay_changed |= annotateDelaysSlews(edge, arc, dcalc_result,
                                           load_pin_index_map, scene, min_max);
    }
    arc_delay_calc->finishDrvrPin();
  }
  return delay_changed;
}

ArcDcalcArgSeq
GraphDelayCalc::makeArcDcalcArgs(Vertex *drvr_vertex,
                                 const MultiDrvrNet *multi_drvr,
                                 Edge *edge,
                                 const TimingArc *arc,
                                 const Scene *scene,
                                 const MinMax *min_max,
                                 ArcDelayCalc *arc_delay_calc)
{
  ArcDcalcArgSeq dcalc_args;
  for (Vertex *drvr_vertex1 : multi_drvr->drvrs()) {
    Edge *edge1 = nullptr;
    const TimingArc *arc1 = nullptr;
    if (drvr_vertex1 == drvr_vertex) {
      edge1 = edge;
      arc1 = arc;
    }
    else
      findParallelEdge(drvr_vertex1, arc, edge1, arc1);
    // Shockingly one fpga vendor connects outputs with no timing arcs together.
    if (edge1) {
      Vertex *from_vertex = edge1->from(graph_);
      const Pin *from_pin = from_vertex->pin();
      const RiseFall *from_rf = arc1->fromEdge()->asRiseFall();
      const RiseFall *drvr_rf = arc1->toEdge()->asRiseFall();
      const Slew in_slew = edgeFromSlew(from_vertex, from_rf, edge1, scene, min_max);

      const Pin *drvr_pin1 = drvr_vertex1->pin();
      float load_cap;
      const Parasitic *parasitic;
      parasiticLoad(drvr_pin1, drvr_rf, scene, min_max, multi_drvr, arc_delay_calc,
                    load_cap, parasitic);
      dcalc_args.emplace_back(from_pin, drvr_pin1, edge1, arc1, in_slew,
                              load_cap, parasitic);
    }
  }
  return dcalc_args;
}

// Find an edge/arc for parallel driver vertex to go along with the
// primary driver drvr_edge/drvr_arc.
void
GraphDelayCalc::findParallelEdge(Vertex *vertex,
                                 const TimingArc *drvr_arc,
                                 // Return values.
                                 Edge *&edge,
                                 const TimingArc *&arc)
{
  LibertyCell *drvr_cell = drvr_arc->from()->libertyCell();
  LibertyCell *vertex_cell = network_->libertyCell(network_->instance(vertex->pin()));
  if (vertex_cell == drvr_cell) {
    // Homogeneous drivers.
    arc = drvr_arc;
    VertexInEdgeIterator edge_iter(vertex, graph_);
    while (edge_iter.hasNext()) {
      edge = edge_iter.next();
      if (edge->timingArcSet() == arc->set()
          && !edge->isBidirectInstPath())
        return;
    }
  }
  else {
    VertexInEdgeIterator edge_iter(vertex, graph_);
    while (edge_iter.hasNext()) {
      edge = edge_iter.next();
      for (TimingArc *arc1 : edge->timingArcSet()->arcs()) {
        if (arc1->fromEdge() == drvr_arc->fromEdge()
            && arc1->toEdge() == drvr_arc->toEdge()
            && !edge->isBidirectInstPath()) {
          arc = arc1;
          return;
        }
      }
    }
  }
  edge = nullptr;
  arc = nullptr;
}

bool
GraphDelayCalc::annotateDelaysSlews(Edge *edge,
                                    const TimingArc *arc,
                                    ArcDcalcResult &dcalc_result,
                                    LoadPinIndexMap &load_pin_index_map,
                                    const Scene *scene,
                                    const MinMax *min_max)
{
  bool delay_changed = annotateDelaySlew(edge, arc,
                                         dcalc_result.gateDelay(),
                                         dcalc_result.drvrSlew(), scene, min_max);
  if (!edge->role()->isLatchDtoQ()) {
    Vertex *drvr_vertex = edge->to(graph_);
    annotateLoadDelays(drvr_vertex, arc->toEdge()->asRiseFall(),
                       dcalc_result,
                       load_pin_index_map, delay_zero, true,
                       scene, min_max);
  }
  return delay_changed;
}

// Annotate the gate delay and merge the slew at the driver pin.
// Annotate the wire delays from the gate output to
// each load pin, and the merge the slews at each load pin. 
bool
GraphDelayCalc::annotateDelaySlew(Edge *edge,
                                  const TimingArc *arc,
                                  const ArcDelay &gate_delay,
                                  const Slew &gate_slew,
                                  const Scene *scene,
                                  const MinMax *min_max)
{
  DcalcAPIndex ap_index = scene->dcalcAnalysisPtIndex(min_max);
  debugPrint(debug_, "delay_calc", 3,
             "  {} {} -> {} {} ({}) scene:{}/{}",
             arc->from()->name(),
             arc->fromEdge()->to_string(),
             arc->to()->name(),
             arc->toEdge()->to_string(),
             arc->role()->to_string(),
             scene->name(),
             min_max->to_string());
  debugPrint(debug_, "delay_calc", 3,
             "    gate delay = {} slew = {}",
             delayAsString(gate_delay, this),
             delayAsString(gate_slew, this));
  bool delay_changed = false;
  Vertex *drvr_vertex = edge->to(graph_);
  const RiseFall *drvr_rf = arc->toEdge()->asRiseFall();
  // Merge slews.
  const Slew drvr_slew = graph_->slew(drvr_vertex, drvr_rf, ap_index);
  if (delayGreater(gate_slew, drvr_slew, min_max, this)
      && !drvr_vertex->slewAnnotated(drvr_rf, min_max)
      && !edge->role()->isLatchDtoQ())
    graph_->setSlew(drvr_vertex, drvr_rf, ap_index, gate_slew);
  if (!graph_->arcDelayAnnotated(edge, arc, ap_index)) {
    const ArcDelay prev_gate_delay = graph_->arcDelay(edge,arc,ap_index);
    float gate_delay1 = delayAsFloat(gate_delay);
    float prev_gate_delay1 = delayAsFloat(prev_gate_delay);
    if (prev_gate_delay1 == 0.0
        || (std::abs(gate_delay1 - prev_gate_delay1) / prev_gate_delay1
            > incremental_delay_tolerance_))
      delay_changed = true;
    graph_->setArcDelay(edge, arc, ap_index, gate_delay);
  }
  return delay_changed;
}

// Annotate wire arc delays and load pin slews.
// extra_delay is additional wire delay to add to delay returned
// by the delay calculator.
void
GraphDelayCalc::annotateLoadDelays(Vertex *drvr_vertex,
                                   const RiseFall *drvr_rf,
                                   ArcDcalcResult &dcalc_result,
                                   LoadPinIndexMap &load_pin_index_map,
                                   const ArcDelay &extra_delay,
                                   bool merge,
                                   const Scene *scene,
                                   const MinMax *min_max)
{
  DcalcAPIndex ap_index = scene->dcalcAnalysisPtIndex(min_max);
  VertexOutEdgeIterator edge_iter(drvr_vertex, graph_);
  while (edge_iter.hasNext()) {
    Edge *wire_edge = edge_iter.next();
    if (wire_edge->isWire()) {
      Vertex *load_vertex = wire_edge->to(graph_);
      Pin *load_pin = load_vertex->pin();
      size_t load_idx = load_pin_index_map[load_pin];
      const ArcDelay &wire_delay = dcalc_result.wireDelay(load_idx);
      const Slew &load_slew = dcalc_result.loadSlew(load_idx);
      debugPrint(debug_, "delay_calc", 3,
                 "    {} load delay = {} slew = {}",
                 load_vertex->to_string(this),
                 delayAsString(wire_delay, this),
                 delayAsString(load_slew, this));
      if (!load_vertex->slewAnnotated(drvr_rf, min_max)) {
        if (drvr_vertex->slewAnnotated(drvr_rf, min_max)) {
          // Copy the driver slew to the load if it is annotated.
          const Slew drvr_slew = graph_->slew(drvr_vertex, drvr_rf, ap_index);
          graph_->setSlew(load_vertex, drvr_rf, ap_index, drvr_slew);
        }
        else {
          const Slew slew = graph_->slew(load_vertex, drvr_rf, ap_index);
          if (!merge
              || delayGreater(load_slew, slew, min_max, this)) {
            graph_->setSlew(load_vertex, drvr_rf, ap_index, load_slew);
          }
        }
      }
      if (!graph_->wireDelayAnnotated(wire_edge, drvr_rf, ap_index)) {
	// Multiple timing arcs with the same output transition
	// annotate the same wire edges so they must be combined
	// rather than set.
	const ArcDelay &delay = graph_->wireArcDelay(wire_edge, drvr_rf, ap_index);
	Delay wire_delay_extra = delaySum(extra_delay, wire_delay, this);
	if (!merge
            || delayGreater(wire_delay_extra, delay, min_max, this)) {
	  graph_->setWireArcDelay(wire_edge, drvr_rf, ap_index, wire_delay_extra);
          if (observer_)
            observer_->delayChangedTo(load_vertex);
	}
      }
    }
  }
}

LoadPinIndexMap
GraphDelayCalc::makeLoadPinIndexMap(Vertex *drvr_vertex)
{
  LoadPinIndexMap load_pin_index_map(network_);
  size_t load_idx = 0;
  VertexOutEdgeIterator edge_iter(drvr_vertex, graph_);
  while (edge_iter.hasNext()) {
    Edge *wire_edge = edge_iter.next();
    if (wire_edge->isWire()) {
      Vertex *load_vertex = wire_edge->to(graph_);
      const Pin *load_pin = load_vertex->pin();
      load_pin_index_map[load_pin] = load_idx;
      load_idx++;
    }
  }
  return load_pin_index_map;
}

// External
float
GraphDelayCalc::loadCap(const Pin *drvr_pin,
                        const Scene *scene,
                        const MinMax *min_max) const
{
  float load_cap = min_max->initValue();
  for (const RiseFall *drvr_rf : RiseFall::range()) {
    float cap = loadCap(drvr_pin, drvr_rf, scene, min_max);
    load_cap = min_max->minMax(cap, load_cap);
  }
  arc_delay_calc_->finishDrvrPin();
  return load_cap;
}

// External
float
GraphDelayCalc::loadCap(const Pin *drvr_pin,
                        const RiseFall *rf,
                        const Scene *scene,
                        const MinMax *min_max) const
{
  float pin_cap, wire_cap;
  loadCap(drvr_pin, rf, scene, min_max, pin_cap, wire_cap);
  return pin_cap + wire_cap;
}

// External
void
GraphDelayCalc::loadCap(const Pin *drvr_pin,
                        const RiseFall *rf,
                        const Scene *scene,
                        const MinMax *min_max,
                        float &pin_cap,
                        float &wire_cap) const
{
  MultiDrvrNet *multi_drvr = nullptr;
  if (graph_) {
    Vertex *drvr_vertex = graph_->pinDrvrVertex(drvr_pin);
    multi_drvr = multiDrvrNet(drvr_vertex);
  }
  const Parasitic *parasitic;
  parasiticLoad(drvr_pin, rf, scene, min_max, multi_drvr, arc_delay_calc_,
                pin_cap, wire_cap, parasitic);
  arc_delay_calc_->finishDrvrPin();
}

float
GraphDelayCalc::loadCap(const Pin *drvr_pin,
                        const RiseFall *rf,
                        const Scene *scene,
                        const MinMax *min_max,
                        ArcDelayCalc *arc_delay_calc) const
{
  const Parasitic *parasitic;
  float pin_cap,  wire_cap;
  parasiticLoad(drvr_pin, rf, scene, min_max, nullptr, arc_delay_calc,
                pin_cap, wire_cap, parasitic);
  return pin_cap + wire_cap;
}

void
GraphDelayCalc::parasiticLoad(const Pin *drvr_pin,
                              const RiseFall *rf,
                              const Scene *scene,
                              const MinMax *min_max,
                              const MultiDrvrNet *multi_drvr,
                              ArcDelayCalc *arc_delay_calc,
                              // Return values.
                              float &load_cap,
                              const Parasitic *&parasitic) const
{
  float pin_cap,  wire_cap;
  parasiticLoad(drvr_pin, rf, scene, min_max, multi_drvr, arc_delay_calc,
                pin_cap, wire_cap, parasitic);
  load_cap = pin_cap + wire_cap;
}

void
GraphDelayCalc::parasiticLoad(const Pin *drvr_pin,
                              const RiseFall *rf,
                              const Scene *scene,
                              const MinMax *min_max,
                              const MultiDrvrNet *multi_drvr,
                              ArcDelayCalc *arc_delay_calc,
                              // Return values.
                              float &pin_cap,
                              float &wire_cap,
                              const Parasitic *&parasitic) const
{
  Parasitics *parasitics = scene->parasitics(min_max);
  bool has_net_load;
  float fanout;
  netCaps(drvr_pin, rf, scene, min_max, multi_drvr,
          pin_cap, wire_cap, fanout, has_net_load);

  parasitic = arc_delay_calc->findParasitic(drvr_pin, rf, scene, min_max);
  // set_load net has precedence over parasitics.
  if (!has_net_load && parasitic) {
    if (parasitics->isParasiticNetwork(parasitic))
      wire_cap += parasitics->capacitance(parasitic);
    else {
      // PiModel includes both pin and external caps.
      float parasitic_cap = parasitics->capacitance(parasitic);
      if (parasitic_cap >= pin_cap)
	wire_cap = parasitic_cap - pin_cap;
      else {
        wire_cap = 0.0;
        // Ignore parasitic if pin cap is greater.
        parasitic = nullptr;
      }
    }
  }
}

void
GraphDelayCalc::netCaps(const Pin *drvr_pin,
                        const RiseFall *rf,
                        const Scene *scene,
                        const MinMax *min_max,
                        // Return values.
                        float &pin_cap,
                        float &wire_cap,
                        float &fanout,
                        bool &has_net_load) const
{
  MultiDrvrNet *multi_drvr = nullptr;
  if (graph_) {
    Vertex *drvr_vertex = graph_->pinDrvrVertex(drvr_pin);
    multi_drvr = multiDrvrNet(drvr_vertex);
  }
  netCaps(drvr_pin, rf, scene, min_max, multi_drvr,
          pin_cap, wire_cap, fanout, has_net_load);
}

void
GraphDelayCalc::netCaps(const Pin *drvr_pin,
                        const RiseFall *rf,
                        const Scene *scene,
                        const MinMax *min_max,
                        const MultiDrvrNet *multi_drvr,
                        // Return values.
                        float &pin_cap,
                        float &wire_cap,
                        float &fanout,
                        bool &has_net_load) const
{
  if (multi_drvr)
    multi_drvr->netCaps(rf, scene, min_max,
			pin_cap, wire_cap, fanout, has_net_load);
  else {
    const Sdc *sdc = scene->sdc();
    // Find pin and external pin/wire capacitance.
    sdc->connectedCap(drvr_pin, rf, scene, min_max,
		       pin_cap, wire_cap, fanout, has_net_load);
  }
}

void
GraphDelayCalc::initSlew(Vertex *vertex)
{
  for (Scene *scene : scenes_) {
    for (const MinMax *min_max : MinMax::range()) {
      DcalcAPIndex ap_index = scene->dcalcAnalysisPtIndex(min_max);
  for (const RiseFall *rf : RiseFall::range()) {
        if (!vertex->slewAnnotated(rf, min_max))
          graph_->setSlew(vertex, rf, ap_index, min_max->initValue());
      }
    }
  }
}

void
GraphDelayCalc::zeroSlewAndWireDelays(Vertex *drvr_vertex,
                                      const RiseFall *rf)
{
  for (Scene *scene : scenes_) {
    for (const MinMax *min_max : MinMax::range()) {
      DcalcAPIndex ap_index = scene->dcalcAnalysisPtIndex(min_max);
      // Init drvr slew.
      if (!drvr_vertex->slewAnnotated(rf, min_max))
        graph_->setSlew(drvr_vertex, rf, ap_index, min_max->initValue());

      // Init wire delays and slews.
      VertexOutEdgeIterator edge_iter(drvr_vertex, graph_);
      while (edge_iter.hasNext()) {
        Edge *wire_edge = edge_iter.next();
        if (wire_edge->isWire()) {
          Vertex *load_vertex = wire_edge->to(graph_);
          if (!graph_->wireDelayAnnotated(wire_edge, rf, ap_index))
            graph_->setWireArcDelay(wire_edge, rf, ap_index, 0.0);
          // Init load vertex slew.
          if (!load_vertex->slewAnnotated(rf, min_max))
            graph_->setSlew(load_vertex, rf, ap_index, 0.0);
        }
      }
    }
  }
}

void
GraphDelayCalc::initWireDelays(Vertex *drvr_vertex)
{
  VertexOutEdgeIterator edge_iter(drvr_vertex, graph_);
  while (edge_iter.hasNext()) {
    Edge *wire_edge = edge_iter.next();
    if (wire_edge->isWire()) {
      for (Scene *scene : scenes_) {
        for (const MinMax *min_max : MinMax::range()) {
          DcalcAPIndex ap_index = scene->dcalcAnalysisPtIndex(min_max);

          Delay delay_init_value(min_max->initValue());
	for (const RiseFall *rf : RiseFall::range()) {
	  if (!graph_->wireDelayAnnotated(wire_edge, rf, ap_index))
	    graph_->setWireArcDelay(wire_edge, rf, ap_index, delay_init_value);
	}
      }
    }
  }
  }
}

Slew
GraphDelayCalc::edgeFromSlew(const Vertex *from_vertex,
                             const RiseFall *from_rf,
                             const Edge *edge,
                             const Scene *scene,
                             const MinMax *min_max)
{
  return edgeFromSlew(from_vertex, from_rf, edge->role(), scene, min_max);
}

// Use clock slew for register/latch clk->q edges.
Slew
GraphDelayCalc::edgeFromSlew(const Vertex *from_vertex,
                             const RiseFall *from_rf,
                             const TimingRole *role,
                             const Scene *scene,
                             const MinMax *min_max)
{
  const ClkNetwork *clk_network = scene->mode()->clkNetwork();
  if (role->genericRole() == TimingRole::regClkToQ()
      && clk_network->isIdealClock(from_vertex))
    return clk_network->idealClkSlew(from_vertex->pin(), from_rf, min_max);
  else {
    DcalcAPIndex ap_index = scene->dcalcAnalysisPtIndex(min_max);
    return graph_->slew(from_vertex, from_rf, ap_index);
  }
}

void
GraphDelayCalc::findCheckEdgeDelays(Edge *edge,
                                    ArcDelayCalc *arc_delay_calc)
{
  Vertex *from_vertex = edge->from(graph_);
  Vertex *to_vertex = edge->to(graph_);
  TimingArcSet *arc_set = edge->timingArcSet();
  const Pin *to_pin = to_vertex->pin();
  Instance *inst = network_->instance(to_pin);
  debugPrint(debug_, "delay_calc", 2, "find check {} {} -> {}",
             sdc_network_->pathName(inst),
             network_->portName(from_vertex->pin()),
             network_->portName(to_pin));
  bool delay_changed = false;
  for (TimingArc *arc : arc_set->arcs()) {
    const RiseFall *from_rf = arc->fromEdge()->asRiseFall();
    const RiseFall *to_rf = arc->toEdge()->asRiseFall();
    if (from_rf && to_rf) {
      const LibertyPort *related_out_port = arc_set->relatedOut();
      const Pin *related_out_pin = nullptr;
      if (related_out_port)
        related_out_pin = network_->findPin(inst, related_out_port);

      for (Scene *scene : scenes_) {
        for (const MinMax *min_max : MinMax::range()) {
          DcalcAPIndex ap_index = scene->dcalcAnalysisPtIndex(min_max);
          if (!graph_->arcDelayAnnotated(edge, arc, ap_index)) {
            const Slew &from_slew = checkEdgeClkSlew(from_vertex, from_rf,
                                                     scene, min_max);
            const Slew to_slew = graph_->slew(to_vertex, to_rf, ap_index);
            debugPrint(debug_, "delay_calc", 3,
                       "  {} {} -> {} {} ({}) scene:{}/{}",
                       arc_set->from()->name(),
                       arc->fromEdge()->to_string(),
                       arc_set->to()->name(),
                       arc->toEdge()->to_string(),
                       arc_set->role()->to_string(),
                       scene->name(),
                       min_max->to_string());
            debugPrint(debug_, "delay_calc", 3,
                       "    from_slew = {} to_slew = {}",
                       delayAsString(from_slew, this),
                       delayAsString(to_slew, this));
            float related_out_cap = 0.0;
            if (related_out_pin)
              related_out_cap = loadCap(related_out_pin, to_rf,scene,min_max,
                                        arc_delay_calc);
            ArcDelay check_delay = arc_delay_calc->checkDelay(to_pin, arc, from_slew,
                                                              to_slew, related_out_cap,
                                                              scene, min_max);
            debugPrint(debug_, "delay_calc", 3,
                       "    check_delay = {}",
                       delayAsString(check_delay, this));
            graph_->setArcDelay(edge, arc, ap_index, check_delay);
            delay_changed = true;
            arc_delay_calc_->finishDrvrPin();
          }
        }
      }
    }
  }

  if (delay_changed && observer_)
    observer_->checkDelayChangedTo(to_vertex);
}

// Use clock slew for timing check clock edges.
Slew
GraphDelayCalc::checkEdgeClkSlew(const Vertex *from_vertex,
                                 const RiseFall *from_rf,
                                 const Scene *scene,
                                 const MinMax *min_max)
{
  const ClkNetwork *clk_network = scene->mode()->clkNetwork();
  if (clk_network->isIdealClock(from_vertex))
    return clk_network->idealClkSlew(from_vertex->pin(), from_rf,
                                      scene->checkClkSlewMinMax(min_max));
  else 
    return graph_->slew(from_vertex, from_rf,
                        scene->checkClkSlewIndex(min_max));
}

////////////////////////////////////////////////////////////////

std::string
GraphDelayCalc::reportDelayCalc(const Edge *edge,
                                const TimingArc *arc,
                                const Scene *scene,
                                const MinMax *min_max,
                                int digits)
{
  Vertex *from_vertex = edge->from(graph_);
  Vertex *to_vertex = edge->to(graph_);
  Pin *to_pin = to_vertex->pin();
  const TimingRole *role = arc->role();
  const Instance *inst = network_->instance(to_pin);
  const TimingArcSet *arc_set = edge->timingArcSet();
  std::string result;
  const RiseFall *from_rf = arc->fromEdge()->asRiseFall();
  const RiseFall *to_rf = arc->toEdge()->asRiseFall();
  if (from_rf && to_rf) {
    const LibertyPort *related_out_port = arc_set->relatedOut();
    const Pin *related_out_pin = nullptr;
    if (related_out_port)
      related_out_pin = network_->findPin(inst, related_out_port);
    float related_out_cap = 0.0;
    if (related_out_pin)
      related_out_cap = loadCap(related_out_pin, to_rf, scene, min_max, arc_delay_calc_);
    if (role->isTimingCheck()) {
      const Slew &from_slew = checkEdgeClkSlew(from_vertex, from_rf, scene, min_max);
      DcalcAPIndex slew_index = scene->dcalcAnalysisPtIndex(min_max);
      const Slew to_slew = graph_->slew(to_vertex, to_rf, slew_index);
      const ClkNetwork *clk_network = scene->mode()->clkNetwork();
      bool from_ideal_clk = clk_network->isIdealClock(from_vertex);
      std::string_view from_slew_annotation =
          from_ideal_clk ? std::string_view(" (ideal clock)") : std::string_view{};
      result = arc_delay_calc_->reportCheckDelay(to_pin, arc, from_slew,
                                                 from_slew_annotation, to_slew,
                                                 related_out_cap, scene, min_max, digits);
    }
    else {
      const Slew from_slew = edgeFromSlew(from_vertex, from_rf, edge, scene, min_max);
      const Parasitic *to_parasitic;
      float load_cap;
      parasiticLoad(to_pin, to_rf, scene, min_max, nullptr, arc_delay_calc_,
                    load_cap, to_parasitic);
      LoadPinIndexMap load_pin_index_map = makeLoadPinIndexMap(to_vertex);
      result = arc_delay_calc_->reportGateDelay(to_pin, arc, from_slew, load_cap,
                                                to_parasitic, load_pin_index_map,
                                                scene, min_max, digits);
    }
    arc_delay_calc_->finishDrvrPin();
  }
  return result;
}

////////////////////////////////////////////////////////////////

void
GraphDelayCalc::minPeriod(const Pin *pin,
                          const Scene *scene,
			  // Return values.
			  float &min_period,
			  bool &exists)
{
  exists = false;
  const MinMax *min_max = MinMax::max();
  const DcalcAPIndex dcalc_ap_index = scene->dcalcAnalysisPtIndex(min_max);
  // Sdf annotation.
  float min_period1 = 0.0;
  bool exists1 = false;
  graph_->periodCheckAnnotation(pin, dcalc_ap_index, min_period, exists);
  if (exists1
      && (!exists || min_period1 < min_period)) {
    min_period = min_period1;
    exists = true;
  }
  if (!exists) {
    // Liberty timing group timing_type minimum_period.
    Vertex *vertex = graph_->pinLoadVertex(pin);
    Edge *edge;
    TimingArc *arc;
    graph_->minPeriodArc(vertex, RiseFall::rise(), edge, arc);
    if (edge) {
      exists = true;
      min_period = delayAsFloat(graph_->arcDelay(edge, arc, dcalc_ap_index));
    }
  }
  if (!exists) {
    // Liberty port min_period attribute.
    LibertyPort *port = network_->libertyPort(pin);
    if (port) {
      Instance *inst = network_->instance(pin);
      for (const Mode *mode : modes_) {
        const Sdc *sdc = mode->sdc();
        OperatingConditions *op_cond = sdc->operatingConditions(min_max);
        const Pvt *pvt = inst ? sdc->pvt(inst, min_max) : nullptr;
        float min_period1 = 0.0;
        bool exists1 = false;
        port->minPeriod(op_cond, pvt, min_period1, exists1);
        if (exists1 
            && (!exists || min_period1 < min_period)) {
          min_period = min_period1;
          exists = true;
        }
      }
    }
  }
}

////////////////////////////////////////////////////////////////

void
MultiDrvrNet::netCaps(const RiseFall *drvr_rf,
                      const Scene *scene,
                      const MinMax *min_max,
		      // Return values.
		      float &pin_cap,
		      float &wire_cap,
		      float &fanout,
		      bool &has_net_load) const
{
  int index = scene->dcalcAnalysisPtIndex(min_max) * RiseFall::index_count
    + drvr_rf->index();
  const NetCaps &net_caps = net_caps_[index];
  pin_cap = net_caps.pinCap();
  wire_cap = net_caps.wireCap();
  fanout = net_caps.fanout();
  has_net_load = net_caps.hasNetLoad();
}

void
MultiDrvrNet::findCaps(const StaState *sta)
{
  int count = RiseFall::index_count * sta->dcalcAnalysisPtCount();
  net_caps_.resize(count);
  const Pin *drvr_pin = dcalc_drvr_->pin();
  for (Scene *scene : sta->scenes()) {
    const Sdc *sdc = scene->sdc();
    for (const MinMax *min_max : MinMax::range()) {
      DcalcAPIndex ap_index = scene->dcalcAnalysisPtIndex(min_max);
    for (const RiseFall *drvr_rf : RiseFall::range()) {
      int drvr_rf_index = drvr_rf->index();
      int index = ap_index * RiseFall::index_count + drvr_rf_index;
      NetCaps &net_caps = net_caps_[index];
      float pin_cap, wire_cap, fanout;
      bool has_net_load;
      // Find pin and external pin/wire capacitance.
        sdc->connectedCap(drvr_pin, drvr_rf, scene, min_max,
			pin_cap, wire_cap, fanout, has_net_load);
      net_caps.init(pin_cap, wire_cap, fanout, has_net_load);
    }
  }
  }
}

void
MultiDrvrNet::setDcalcDrvr(Vertex *drvr)
{
  dcalc_drvr_ = drvr;
}

bool
MultiDrvrNet::parallelGates(const Network *network) const
{
  return network->direction(dcalc_drvr_->pin())->isOutput();
}

} // namespace sta