rewrite functional backend test code in python

tests/functional/vcd_harness.cc

@@ -0,0 +1,125 @@
+#include <cstdio>
+#include <iostream>
+#include <fstream>
+#include <random>
+
+#include "my_module_functional_cxx.cc"
+
+struct DumpHeader {
+  std::ofstream &ofs;
+  DumpHeader(std::ofstream &ofs) : ofs(ofs) {}
+  template <size_t n>
+  void operator()(const char *name, Signal<n> value) {
+    ofs << "$var wire " << n << " " << name[0] << " " << name << " $end\n";
+  }
+};
+
+struct Dump {
+  std::ofstream &ofs;
+  Dump(std::ofstream &ofs) : ofs(ofs) {}
+  template <size_t n>
+  void operator()(const char *name, Signal<n> value) {
+    // Bit
+    if (n == 1) {
+      ofs << (value[0] ? '1' : '0');
+      ofs << name[0] << "\n";
+      return;
+    }
+    // vector (multi-bit) signals
+    ofs << "b";
+    for (size_t i = n; i-- > 0;)
+      ofs << (value[i] ? '1' : '0');
+    ofs << " " << name[0] << "\n";
+  }
+};
+
+template<size_t n>
+Signal<n> random_signal(std::mt19937 &gen) {
+  std::uniform_int_distribution<uint32_t> dist;
+  std::array<uint32_t, (n+31)/32> words;
+  for(auto &w : words)
+    w = dist(gen);
+  return Signal<n>::from_array(words);
+}
+
+struct Reset {
+  template <size_t n>
+  void operator()(const char *, Signal<n> &signal) {
+    signal = 0;
+  }
+};
+
+struct Randomize {
+  std::mt19937 &gen;
+  Randomize(std::mt19937 &gen) : gen(gen) {}
+
+  template <size_t n>
+  void operator()(const char *, Signal<n> &signal) {
+    signal = random_signal<n>(gen);
+  }
+};
+
+int main(int argc, char **argv)
+{
+  if (argc != 2) {
+    std::cerr << "Usage: " << argv[0] << " <functional_vcd_filename>\n";
+    return 1;
+  }
+
+  const std::string functional_vcd_filename = argv[1];
+
+  constexpr int steps = 1000;
+  constexpr int number_timescale = 1;
+  const std::string units_timescale = "us";
+  gold::Inputs inputs;
+  gold::Outputs outputs;
+  gold::State state;
+  gold::State next_state;
+
+  std::ofstream vcd_file(functional_vcd_filename);
+
+  vcd_file << "$timescale " << number_timescale << " " << units_timescale << " $end\n";
+  vcd_file << "$scope module gold $end\n";
+  {
+    DumpHeader d(vcd_file);
+    inputs.visit(d);
+    outputs.visit(d);
+    state.visit(d);
+  }
+  vcd_file << "$enddefinitions $end\n$dumpvars\n";
+  vcd_file << "#0\n";
+  // Set all signals to false
+  inputs.visit(Reset());
+
+  gold::eval(inputs, outputs, state, next_state);
+  {
+    Dump d(vcd_file);
+    inputs.visit(d);
+    outputs.visit(d);
+    state.visit(d);
+  }
+
+  // Initialize random number generator once
+  std::random_device rd;
+  std::mt19937 gen(rd());
+
+  for (int step = 0; step < steps; ++step) {
+    // Functional backend cxx
+    vcd_file << "#" << (step + 1) << "\n";
+    inputs.visit(Randomize(gen));
+
+    gold::eval(inputs, outputs, state, next_state);
+    {
+      Dump d(vcd_file);
+      inputs.visit(d);
+      outputs.visit(d);
+      state.visit(d);
+    }
+
+    state = next_state;
+  }
+
+  vcd_file.close();
+
+  return 0;
+}