offline-ctc-greedy-search-decoder.cc
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// sherpa-onnx/csrc/offline-ctc-greedy-search-decoder.h
//
// Copyright (c) 2023 Xiaomi Corporation
#include "sherpa-onnx/csrc/offline-ctc-greedy-search-decoder.h"
#include <algorithm>
#include <utility>
#include <vector>
#include "sherpa-onnx/csrc/macros.h"
namespace sherpa_onnx {
std::vector<OfflineCtcDecoderResult> OfflineCtcGreedySearchDecoder::Decode(
Ort::Value log_probs, Ort::Value log_probs_length) {
std::vector<int64_t> shape = log_probs.GetTensorTypeAndShapeInfo().GetShape();
int32_t batch_size = static_cast<int32_t>(shape[0]);
int32_t num_frames = static_cast<int32_t>(shape[1]);
int32_t vocab_size = static_cast<int32_t>(shape[2]);
const int64_t *p_log_probs_length = log_probs_length.GetTensorData<int64_t>();
std::vector<OfflineCtcDecoderResult> ans;
ans.reserve(batch_size);
for (int32_t b = 0; b != batch_size; ++b) {
const float *p_log_probs =
log_probs.GetTensorData<float>() + b * num_frames * vocab_size;
OfflineCtcDecoderResult r;
int64_t prev_id = -1;
for (int32_t t = 0; t != static_cast<int32_t>(p_log_probs_length[b]); ++t) {
auto y = static_cast<int64_t>(std::distance(
static_cast<const float *>(p_log_probs),
std::max_element(
static_cast<const float *>(p_log_probs),
static_cast<const float *>(p_log_probs) + vocab_size)));
p_log_probs += vocab_size;
if (y != blank_id_ && y != prev_id) {
r.tokens.push_back(y);
r.timestamps.push_back(t);
}
prev_id = y;
} // for (int32_t t = 0; ...)
ans.push_back(std::move(r));
}
return ans;
}
} // namespace sherpa_onnx