add modified beam search (#69)

sherpa-onnx/csrc/onnx-utils.cc

@@ -44,6 +44,38 @@ void GetOutputNames(Ort::Session *sess, std::vector<std::string> *output_names,
   }
 }
 
+Ort::Value GetEncoderOutFrame(OrtAllocator *allocator, Ort::Value *encoder_out,
+                              int32_t t) {
+  std::vector<int64_t> encoder_out_shape =
+      encoder_out->GetTensorTypeAndShapeInfo().GetShape();
+
+  auto batch_size = encoder_out_shape[0];
+  auto num_frames = encoder_out_shape[1];
+  assert(t < num_frames);
+
+  auto encoder_out_dim = encoder_out_shape[2];
+
+  auto offset = num_frames * encoder_out_dim;
+
+  auto memory_info =
+      Ort::MemoryInfo::CreateCpu(OrtDeviceAllocator, OrtMemTypeDefault);
+
+  std::array<int64_t, 2> shape{batch_size, encoder_out_dim};
+
+  Ort::Value ans =
+      Ort::Value::CreateTensor<float>(allocator, shape.data(), shape.size());
+
+  float *dst = ans.GetTensorMutableData<float>();
+  const float *src = encoder_out->GetTensorData<float>();
+
+  for (int32_t i = 0; i != batch_size; ++i) {
+    std::copy(src + t * encoder_out_dim, src + (t + 1) * encoder_out_dim, dst);
+    src += offset;
+    dst += encoder_out_dim;
+  }
+  return ans;
+}
+
 void PrintModelMetadata(std::ostream &os, const Ort::ModelMetadata &meta_data) {
   Ort::AllocatorWithDefaultOptions allocator;
   std::vector<Ort::AllocatedStringPtr> v =