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ClipGraphExtract

  • An example repo for adding the tool to the top-level app and using an OpenDB-C++ API for DAC 2020 tutorial 9.
  • The base sources are copied from OpenROAD repo, commit: 7156dc. Unessential repos are removed to be compiled well in other environments.
  • Please read the doc/OpenRoadArch.md to understand the requirement. The ClipGraphExtract follows the OpenRoadArch.md manual.

ClipGraphExtract Flow
Clique and star net decomposition example
  • In OpenROAD app, read_lef and read_def command will populate the OpenDB's data structure.
  • Using OpenDB's C++ API, save all instances' bbox to Boost/RTree structure.
  • Send a region query to RTree to extract related instances using the clips' coordinates.
  • Generate clip graph's clique/star net models as text file (e.g. edges list) for graph neural network models.

File Structure

  • include/openroad/

    • public headers location of OpenROAD.

  • src/

    • OpenROAD source code files. The tools source code should be located here.

  • src/ClipGraphExtractor/src/

    • source code location of ClipGraphExtractor.

  • src/ClipGraphExtractor/include/clip_graph_ext/

    • public headers location of ClipGraphExtractor.

Implementation Details

OpenDB C++ API

  • All the OpenDB reference is in the OpenDB's public header (OpenDB/include/opendb/db.h). Please check this header file first to understand how the structures are designed.

  • Set the OpenDB pointer from Top-level app (Link)

    void 
initClipGraphExtractor(OpenRoad *openroad) 
{
  Tcl_Interp* tcl_interp = openroad->tclInterp();
  Clipgraphextractor_Init(tcl_interp);
  sta::evalTclInit(tcl_interp, sta::graph_extractor_tcl_inits);
  openroad->getClipGraphExtractor()->setDb(openroad->getDb());
  openroad->getClipGraphExtractor()->setSta(openroad->getSta());
}

  • Push instances' location to RTree using dbInst* (Link)

    dbBlock* block = db_->getChip()->getBlock();
for( dbInst* inst : block->getInsts() ) {
  dbBox* bBox = inst->getBBox();
  box b (point(bBox->xMin(), bBox->yMin()), 
          point(bBox->xMax(), bBox->yMax()));
  rTree->insert( make_pair(b, inst) );
}

  • Send region query using given bbox coordinates. (Link)

    box queryBox( point(lx, ly), point(ux, uy) );

vector<value> foundInsts; 
rTree->query(bgi::intersects(queryBox), 
    std::back_inserter(foundInsts));

cout << "NumFoundInsts: " << foundInsts.size() << endl;

  • Store distinctive instances into hash_set (e.g. std::set<dbInst*>) (Link)

    set<odb::dbInst*> instSet;
for(value& val : foundInsts) {
  odb::dbInst* inst = val.second;
  instSet.insert( inst ); 
}

  • Extract distinctive dbITerms from dbInst objects (Link)

    for(odb::dbITerm* iTerm : inst->getITerms()) {
  if( iTerm->getSigType() == odb::dbSigType::POWER ||
      iTerm->getSigType() == odb::dbSigType::GROUND ) {
    continue;
  }
  iTermSet.insert(iTerm); 
}

  • Extract distinctive dbNet from dbITerm objects (Link)

    // extract Net
set<odb::dbNet*> netSet;
for(odb::dbITerm* iTerm : iTermSet) {
  odb::dbNet* net = iTerm->getNet();
  if (!net) { 
    continue;
  }
  if( net->getSigType() == odb::dbSigType::POWER ||
      net->getSigType() == odb::dbSigType::GROUND ||
      net->getSigType() == odb::dbSigType::CLOCK ) {
    continue;
  }
  netSet.insert(net);
}

Adding a Tool

  • Write tool's CMakeLists.txt (src/ClipGraphExtract/CMakeLists.txt)

  • Modify OpenROAD's CMakeLists.txt accordingly (src/CMakeLists.txt)

    • (Link)

      set(CLIP_GRAPHEXT_HOME ${PROJECT_SOURCE_DIR}/src/ClipGraphExtract)

    • (Link)

      add_subdirectory(ClipGraphExtract)

    • (Link)

      target_link_libraries(openroad
...
ClipGraphExtractor
...
)

  • Write an initializing public header inside tool (Link)

    namespace ord {
class OpenRoad;

ClipGraphExtract::ClipGraphExtractor* makeClipGraphExtractor();
void initClipGraphExtractor(OpenRoad *openroad);
void deleteClipGraphExtractor(ClipGraphExtract::ClipGraphExtractor *graphext);
}

  • Change OpenRoad.cc and OpenRoad.hh accordinly

    • include/openroad/OpenRoad.hh

      // incomplete header
namespace ClipGraphExtract {
class ClipGraphExtractor;
}

...
// getter functions
ClipGraphExtract::ClipGraphExtractor *getClipGraphExtractor() { return clipGraphExt_; }
...
// private variable
ClipGraphExtract::ClipGraphExtractor *clipGraphExt_;

    • src/OpenRoad.cc

      // make
clipGraphExt_ = makeClipGraphExtractor();
...
// delete
deleteClipGraphExtractor(clipGraphExt_);
...
// init
initClipGraphExtractor(this);
...

  • Registering Hidden Tcl Command using SWIG (src/ClipGraphExtract/src/clipGraphExtract.i)

    // Note that hidden SWIG tcl commands must have *_cmd as a function name.
void
graph_extract_cmd(int lx, int ly, int ux, int uy) 
{
  ClipGraphExtractor* graphExt = getClipGraphExtractor();
  graphExt->extract(lx, ly, ux, uy);
}

  • Registering Visible Tcl Command using OpenSTA Tcl Template (src/ClipGraphExtract/src/clipGraphExtract.tcl)

    // register graph_extract commands in OpenROAD binary.
sta::define_cmd_args "graph_extract" {
  [-graph_model star/clique]\
  [-edge_weight_model weight]\
  [-out_file fileName]
}

// function details
proc graph_extract { args } {
...
// *_cmd SWIG functions can be used in here.
...
}

How to build/test?

  • Build

    • Please follow the build manual in OpenROAD

      $ mkdir build
$ cd build
$ cmake ..
$ make

  • Test on ClipGraphExtract

    $ cd src/ClipGraphExtract/test/
$ ../../../build/src/openroad test.tcl

License

  • BSD-3-Clause license.
  • Code found under the subdirectory (e.g., src/OpenSTA) have individual copyright and license declarations at each folder.