visualize FSA via GraphViz.

Author: csukuangfj

k2/csrc/CMakeLists.txt

@@ -6,6 +6,10 @@ add_library(fsa_util fsa_util.cc)
 target_include_directories(fsa_util PUBLIC ${CMAKE_SOURCE_DIR})
 target_compile_features(fsa_util PUBLIC cxx_std_11)
 
+add_library(fsa_renderer fsa_renderer.cc)
+target_include_directories(fsa_renderer PUBLIC ${CMAKE_SOURCE_DIR})
+target_compile_features(fsa_renderer PUBLIC cxx_std_11)
+
 add_executable(properties_test properties_test.cc)
 
 target_link_libraries(properties_test
@@ -34,4 +38,18 @@ add_test(NAME Test.fsa_util_test
     $<TARGET_FILE:fsa_util_test>
 )
 
+add_executable(fsa_renderer_test fsa_renderer_test.cc)
+
+target_link_libraries(fsa_renderer_test
+  PRIVATE
+    fsa_renderer
+    gtest
+    gtest_main
+)
+
+add_test(NAME Test.fsa_renderer_test
+  COMMAND
+    $<TARGET_FILE:fsa_renderer_test>
+)
+
 # TODO(fangjun): write some helper functions to create targets.

k2/csrc/fsa_renderer.cc

@@ -0,0 +1,85 @@
+// k2/csrc/fsa_renderer.cc
+
+// Copyright (c)  2020  Fangjun Kuang (csukuangfj@gmail.com)
+
+// See ../../LICENSE for clarification regarding multiple authors
+
+#include "k2/csrc/fsa_renderer.h"
+
+#include <sstream>
+#include <string>
+
+namespace {
+
+std::string GeneratePrologue() {
+  // TODO(fangjun): the following options can be passed from outside
+  std::string header = R"header(
+digraph FSA {
+  rankdir = LR;
+  size = "8.5,11";
+  label = "";
+  center = 1;
+  orientation = Portrait;
+  ranksep = "0.4"
+  nodesep = "0.25"
+)header";
+  return header;
+}
+
+std::string GenerateEpilogue() { return "}"; }
+
+using k2::Arc;
+using k2::Fsa;
+using k2::Label;
+using k2::StateId;
+
+std::string ProcessState(const Fsa &fsa, int32_t state) {
+  std::ostringstream os;
+  os << "  " << state << " [label = \"" << state
+     << "\", shape = circle, style = bold, fontsize=14]"
+     << "\n";
+
+  int32_t begin = fsa.leaving_arcs[state].begin;
+  int32_t end = fsa.leaving_arcs[state].end;
+
+  for (; begin != end; ++begin) {
+    const auto &arc = fsa.arcs[begin];
+    StateId src = arc.src_state;
+    StateId dest = arc.dest_state;
+    Label label = arc.label;
+    os << "          " << src << " -> " << dest << " [label = \"" << label
+       << "\", fontsize = 14];"
+       << "\n";
+  }
+
+  return os.str();
+}
+
+}  // namespace
+
+namespace k2 {
+
+FsaRenderer::FsaRenderer(const Fsa &fsa) : fsa_(fsa) {}
+
+std::string FsaRenderer::Render() const {
+  int32_t num_states = fsa_.NumStates();
+  if (num_states == 0) return "";
+
+  std::ostringstream os;
+  os << GeneratePrologue();
+
+  for (int32_t i = 0; i != num_states - 1; ++i) {
+    os << ProcessState(fsa_, i);
+  }
+
+  // now for the final state
+  os << "  " << (num_states - 1) << " [label = \"" << (num_states - 1)
+     << "\", shape = doublecircle, style = solid, fontsize = 14]"
+     << "\n";
+
+  os << GenerateEpilogue() << "\n";
+
+  return os.str();
+}
+
+}  // namespace k2

k2/csrc/fsa_renderer.h

@@ -0,0 +1,30 @@
+// k2/csrc/fsa_renderer.h
+
+// Copyright (c)  2020  Fangjun Kuang (csukuangfj@gmail.com)
+
+// See ../../LICENSE for clarification regarding multiple authors
+
+#include <string>
+
+#include "k2/csrc/fsa.h"
+
+#ifndef K2_CSRC_FSA_RENDERER_H_
+#define K2_CSRC_FSA_RENDERER_H_
+
+namespace k2 {
+
+// Get a GraphViz representation of an fsa.
+class FsaRenderer {
+ public:
+  explicit FsaRenderer(const Fsa &fsa);
+
+  // Return a GraphViz representation of the fsa
+  std::string Render() const;
+
+ private:
+  const Fsa &fsa_;
+};
+
+}  // namespace k2
+
+#endif  // K2_CSRC_FSA_RENDERER_H_

k2/csrc/fsa_renderer_test.cc

@@ -0,0 +1,42 @@
+// k2/csrc/fsa_renderer_test.cc
+
+// Copyright (c)  2020  Fangjun Kuang (csukuangfj@gmail.com)
+
+// See ../../LICENSE for clarification regarding multiple authors
+
+#include "k2/csrc/fsa_renderer.h"
+
+#include <utility>
+#include <vector>
+
+#include "gtest/gtest.h"
+
+namespace k2 {
+
+// NOTE(fangjun): this test always passes.
+// Its purpose is to get a Graphviz representation
+// of the fsa and convert it to a viewable format **offline**.
+//
+// For example, you can run
+//
+//  ./k2/csrc/fsa_renderer_test 2>&1 >/dev/null | dot -Tpdf > test.pdf
+//
+// and then open the generated "test.pdf" to verify FsaRenderer works
+// as expected.
+TEST(FsaRenderer, Render) {
+  std::vector<Arc> arcs = {
+      {0, 1, 2}, {0, 2, 1}, {1, 2, 0}, {1, 3, 5}, {2, 3, 6},
+  };
+  std::vector<Range> leaving_arcs = {
+      {0, 2}, {2, 4}, {4, 5}, {0, 0},  // the last state has no leaving arcs
+  };
+
+  Fsa fsa;
+  fsa.leaving_arcs = std::move(leaving_arcs);
+  fsa.arcs = std::move(arcs);
+
+  FsaRenderer renderer(fsa);
+  std::cerr << renderer.Render();
+}
+
+}  // namespace k2

k2/csrc/fsa_util.cc

@@ -14,9 +14,9 @@ namespace k2 {
 void GetEnteringArcs(const Fsa &fsa, VecOfVec *entering_arcs) {
   // CHECK(CheckProperties(fsa, KTopSorted));
 
-  int num_states = fsa.NumStates();
+  int32_t num_states = fsa.NumStates();
   std::vector<std::vector<std::pair<Label, StateId>>> vec(num_states);
-  int num_arcs = 0;
+  int32_t num_arcs = 0;
   for (const auto &arc : fsa.arcs) {
     auto src_state = arc.src_state;
     auto dest_state = arc.dest_state;
@@ -27,6 +27,8 @@ void GetEnteringArcs(const Fsa &fsa, VecOfVec *entering_arcs) {
 
   auto &ranges = entering_arcs->ranges;
   auto &values = entering_arcs->values;
+  ranges.clear();
+  values.clear();
   ranges.reserve(num_states);
   values.reserve(num_arcs);
 

k2/csrc/fsa_util_test.cc

@@ -18,7 +18,7 @@ TEST(FsaUtil, GetEnteringArcs) {
       {0, 1, 2}, {0, 2, 1}, {1, 2, 0}, {1, 3, 5}, {2, 3, 6},
   };
   std::vector<Range> leaving_arcs = {
-      {0, 2}, {2, 4}, {4, 5}, {0, 0},  // the last state has no entering arcs
+      {0, 2}, {2, 4}, {4, 5}, {0, 0},  // the last state has no leaving arcs
   };
 
   Fsa fsa;