Support sharing memory with log_probs in DecodableCtc. (#5)

CMakeLists.txt

@@ -9,7 +9,7 @@ if (CMAKE_VERSION VERSION_GREATER_EQUAL "3.24.0")
   cmake_policy(SET CMP0135 NEW)
 endif()
 
-set(KALDI_DECODER_VERSION "0.2.2")
+set(KALDI_DECODER_VERSION "0.2.3")
 
 set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/lib")
 set(CMAKE_LIBRARY_OUTPUT_DIRECTORY "${CMAKE_BINARY_DIR}/lib")

kaldi-decoder/csrc/decodable-ctc.cc

@@ -8,20 +8,28 @@
 
 namespace kaldi_decoder {
 
-DecodableCtc::DecodableCtc(const FloatMatrix &feats) : feature_matrix_(feats) {}
+DecodableCtc::DecodableCtc(const FloatMatrix &log_probs)
+    : log_probs_(log_probs) {
+  p_ = &log_probs_(0, 0);
+  num_rows_ = log_probs_.rows();
+  num_cols_ = log_probs_.cols();
+}
+
+DecodableCtc::DecodableCtc(const float *p, int32_t num_rows, int32_t num_cols)
+    : p_(p), num_rows_(num_rows), num_cols_(num_cols) {}
 
 float DecodableCtc::LogLikelihood(int32_t frame, int32_t index) {
   // Note: We need to use index - 1 here since
   // all the input labels of the H are incremented during graph
   // construction
   assert(index >= 1);
 
-  return feature_matrix_(frame, index - 1);
+  return *(p_ + frame * num_cols_ + index - 1);
 }
 
-int32_t DecodableCtc::NumFramesReady() const { return feature_matrix_.rows(); }
+int32_t DecodableCtc::NumFramesReady() const { return num_rows_; }
 
-int32_t DecodableCtc::NumIndices() const { return feature_matrix_.cols(); }
+int32_t DecodableCtc::NumIndices() const { return num_cols_; }
 
 bool DecodableCtc::IsLastFrame(int32_t frame) const {
   assert(frame < NumFramesReady());

kaldi-decoder/csrc/decodable-ctc.h

@@ -12,7 +12,15 @@ namespace kaldi_decoder {
 
 class DecodableCtc : public DecodableInterface {
  public:
-  explicit DecodableCtc(const FloatMatrix &feats);
+  // It copies the input log_probs
+  explicit DecodableCtc(const FloatMatrix &log_probs);
+
+  // It shares the memory with the input array.
+  //
+  // @param p Pointer to a 2-d array of shape (num_rows, num_cols).
+  //          The array should be kept alive as long as this object is still
+  //          alive.
+  DecodableCtc(const float *p, int32_t num_rows, int32_t num_cols);
 
   float LogLikelihood(int32_t frame, int32_t index) override;
 
@@ -25,7 +33,11 @@ class DecodableCtc : public DecodableInterface {
 
  private:
   // it saves log_softmax output
-  FloatMatrix feature_matrix_;
+  FloatMatrix log_probs_;
+
+  const float *p_ = nullptr;  // pointer to a 2-d array
+  int32_t num_rows_;          // number of rows in the 2-d array
+  int32_t num_cols_;          // number of cols in the 2-d array
 };
 
 }  // namespace kaldi_decoder