add pad_sequence (#84)

@@ -16,6 +16,7 @@ set(sources
   online-transducer-modified-beam-search-decoder.cc
   online-zipformer-transducer-model.cc
   onnx-utils.cc
+  pad-sequence.cc
   parse-options.cc
   resample.cc
   slice.cc
@@ -122,6 +123,7 @@ endif()
 if(SHERPA_ONNX_ENABLE_TESTS)
   set(sherpa_onnx_test_srcs
     cat-test.cc
+    pad-sequence-test.cc
     slice-test.cc
     transpose-test.cc
     unbind-test.cc

+// sherpa-onnx/csrc/pad-sequence-test.cc
+//
+// Copyright (c)  2023  Xiaomi Corporation
+
+#include "sherpa-onnx/csrc/pad-sequence.h"
+
+#include <numeric>
+
+#include "gtest/gtest.h"
+#include "sherpa-onnx/csrc/onnx-utils.h"
+
+namespace sherpa_onnx {
+
+TEST(PadSequence, ThreeTensors) {
+  Ort::AllocatorWithDefaultOptions allocator;
+
+  std::array<int64_t, 2> shape1{3, 5};
+  Ort::Value v1 =
+      Ort::Value::CreateTensor<float>(allocator, shape1.data(), shape1.size());
+  float *p1 = v1.GetTensorMutableData<float>();
+  std::iota(p1, p1 + shape1[0] * shape1[1], 0);
+
+  std::array<int64_t, 2> shape2{4, 5};
+  Ort::Value v2 =
+      Ort::Value::CreateTensor<float>(allocator, shape2.data(), shape2.size());
+  float *p2 = v2.GetTensorMutableData<float>();
+  std::iota(p2, p2 + shape2[0] * shape2[1], 0);
+
+  std::array<int64_t, 2> shape3{2, 5};
+  Ort::Value v3 =
+      Ort::Value::CreateTensor<float>(allocator, shape3.data(), shape3.size());
+  float *p3 = v3.GetTensorMutableData<float>();
+  std::iota(p3, p3 + shape3[0] * shape3[1], 0);
+
+  auto ans = PadSequence(allocator, {&v1, &v2, &v3}, -1);
+
+  Print2D(&v1);
+  Print2D(&v2);
+  Print2D(&v3);
+  Print3D(&ans);
+}
+
+}  // namespace sherpa_onnx

+// sherpa-onnx/csrc/pad-sequence.cc
+//
+// Copyright (c)  2023  Xiaomi Corporation
+
+#include "sherpa-onnx/csrc/pad-sequence.h"
+
+#include <assert.h>
+
+#include <algorithm>
+#include <vector>
+
+namespace sherpa_onnx {
+
+Ort::Value PadSequence(OrtAllocator *allocator,
+                       const std::vector<const Ort::Value *> &values,
+                       float padding_value) {
+  int32_t batch_size = static_cast<int32_t>(values.size());
+
+  std::vector<int64_t> shape0 =
+      values[0]->GetTensorTypeAndShapeInfo().GetShape();
+  assert(shape0.size() == 2);
+
+  auto feature_dim = shape0[1];
+  auto max_T = shape0[0];
+
+  for (int32_t i = 1; i != batch_size; ++i) {
+    auto shape = values[i]->GetTensorTypeAndShapeInfo().GetShape();
+
+    assert(shape.size() == 2);
+    assert(shape[1] == feature_dim);
+
+    max_T = std::max(max_T, shape[0]);
+  }
+  std::array<int64_t, 3> ans_shape{batch_size, max_T, feature_dim};
+
+  Ort::Value ans = Ort::Value::CreateTensor<float>(allocator, ans_shape.data(),
+                                                   ans_shape.size());
+  float *dst = ans.GetTensorMutableData<float>();
+  std::fill(dst, dst + batch_size * max_T * feature_dim, padding_value);
+
+  for (const auto *v : values) {
+    const float *src = v->GetTensorData<float>();
+    auto shape = v->GetTensorTypeAndShapeInfo().GetShape();
+    std::copy(src, src + shape[0] * shape[1], dst);
+    dst += max_T * feature_dim;
+  }
+
+  return ans;
+
+  // TODO(fangjun): Check that the returned value is correct.
+}
+
+}  // namespace sherpa_onnx

+// sherpa-onnx/csrc/pad-sequence.h
+//
+// Copyright (c)  2023  Xiaomi Corporation
+#ifndef SHERPA_ONNX_CSRC_PAD_SEQUENCE_H_
+#define SHERPA_ONNX_CSRC_PAD_SEQUENCE_H_
+
+#include <vector>
+
+#include "onnxruntime_cxx_api.h"  // NOLINT
+
+namespace sherpa_onnx {
+
+/** Similar to torch.nn.utils.rnn.pad_sequence but it supports only
+ * batch_first=true.
+ *
+ * @param allocator
+ * @param values A list of 2-D tensors. Each tensor's second dimension
+ *               must be the same and the data type of each tensor should
+ *               be float.
+ * @param padding_value Value used for padding. For log-fbank, you usually use
+ *                      -23.025850929940457f as the padding value.
+ *
+ * @return Return a 3-D tensor of shape (B, max_T, C).
+ */
+Ort::Value PadSequence(OrtAllocator *allocator,
+                       const std::vector<const Ort::Value *> &values,
+                       float padding_value);
+
+}  // namespace sherpa_onnx
+
+#endif  // SHERPA_ONNX_CSRC_PAD_SEQUENCE_H_