Simple Place Delay Model Read/Write

vpr/src/place/place_delay_model.cpp

@@ -170,6 +170,14 @@ float SimpleDelayModel::delay(const t_physical_tile_loc& from_loc, int /*from_pi
         "is disable because VTR_ENABLE_CAPNPROTO=OFF." \
         "Re-compile with CMake option VTR_ENABLE_CAPNPROTO=ON to enable."
 
+void SimpleDelayModel::read(const std::string& /*file*/) {
+    VPR_THROW(VPR_ERROR_PLACE, "SimpleDelayModel::read " DISABLE_ERROR);
+}
+
+void SimpleDelayModel::write(const std::string& /*file*/) const {
+    VPR_THROW(VPR_ERROR_PLACE, "SimpleDelayModel::write " DISABLE_ERROR);
+}
+
 void DeltaDelayModel::read(const std::string& /*file*/) {
     VPR_THROW(VPR_ERROR_PLACE, "DeltaDelayModel::read " DISABLE_ERROR);
 }
@@ -198,6 +206,64 @@ static void FromFloat(VprFloatEntry::Builder* out, const float& in) {
     out->setValue(in);
 }
 
+void SimpleDelayModel::read(const std::string& file) {
+    // MmapFile object creates an mmap of the specified path, and will munmap
+    // when the object leaves scope.
+    MmapFile f(file);
+
+    /* Increase reader limit to 1G words to allow for large files. */
+    ::capnp::ReaderOptions opts = default_large_capnp_opts();
+
+    // FlatArrayMessageReader is used to read the message from the data array
+    // provided by MmapFile.
+    ::capnp::FlatArrayMessageReader reader(f.getData(), opts);
+
+    // When reading capnproto files the Reader object to use is named
+    // <schema name>::Reader.
+    //
+    // Initially this object is an empty VprDeltaDelayModel.
+    VprDeltaDelayModel::Reader model;
+
+    // The reader.getRoot performs a cast from the generic capnproto to fit
+    // with the specified schema.
+    //
+    // Note that capnproto does not validate that the incoming data matches the
+    // schema.  If this property is required, some form of check would be
+    // required.
+    model = reader.getRoot<VprDeltaDelayModel>();
+
+    // ToNdMatrix is a generic function for converting a Matrix capnproto
+    // to a vtr::NdMatrix.
+    //
+    // The user must supply the matrix dimension (5 in this case), the source
+    // capnproto type (VprFloatEntry),
+    // target C++ type (flat), and a function to convert from the source capnproto
+    // type to the target C++ type (ToFloat).
+    //
+    // The second argument should be of type Matrix<X>::Reader where X is the
+    // capnproto element type.
+    ToNdMatrix<5, VprFloatEntry, float>(&delays_, model.getDelays(), ToFloat);
+}
+
+void SimpleDelayModel::write(const std::string& file) const {
+    // MallocMessageBuilder object generates capnproto message builder,
+    // using malloc for buffer allocation.
+    ::capnp::MallocMessageBuilder builder;
+
+    // initRoot<X> returns a X::Builder object that can be used to set the
+    // fields in the message.
+    auto model = builder.initRoot<VprDeltaDelayModel>();
+
+    // FromNdMatrix is a generic function for converting a vtr::NdMatrix to a
+    // Matrix message.  It is the mirror function of ToNdMatrix described in
+    // read above.
+    auto delay_values = model.getDelays();
+    FromNdMatrix<5, VprFloatEntry, float>(&delay_values, delays_, FromFloat);
+
+    // writeMessageToFile writes message to the specified file.
+    writeMessageToFile(file, &builder);
+}
+
 void DeltaDelayModel::read(const std::string& file) {
     // MmapFile object creates an mmap of the specified path, and will munmap
     // when the object leaves scope.

vpr/src/place/place_delay_model.h

@@ -235,6 +235,15 @@ class SimpleDelayModel : public PlaceDelayModel {
   public:
     SimpleDelayModel() {}
 
+    /**
+     * @brief Initializes the `delays_` data structure. This involves retrieving the corresponding delays for each entry from
+     * the router lookahead and storing the minimum among them.
+     *
+     * @param router The router used to retrieve information from the router lookahead.
+     * @param placer_opts Placment parameters.
+     * @param router_opts Routing parameters.
+     * @param longest_length The length of the longest routing track.
+    */
     void compute(
         RouterDelayProfiler& router,
         const t_placer_opts& placer_opts,
@@ -243,8 +252,14 @@ class SimpleDelayModel : public PlaceDelayModel {
     float delay(const t_physical_tile_loc& from_loc, int /*from_pin*/, const t_physical_tile_loc& to_loc, int /*to_pin*/) const override;
     void dump_echo(std::string /*filepath*/) const override {}
 
-    void read(const std::string& /*file*/) override {}
-    void write(const std::string& /*file*/) const override {}
+    void read(const std::string& /*file*/) override;
+    void write(const std::string& /*file*/) const override;
+    /**
+     @brief Returns a reference to the array containing the placement delay matrix.
+    */
+    const vtr::NdMatrix<float, 5>& delays() const {
+        return delays_;
+    }
 
   private:
     /**