Add lm rescore to online-modified-beam-search (#133)

sherpa-onnx/csrc/online-rnn-lm.h

@@ -0,0 +1,48 @@
+// sherpa-onnx/csrc/online-rnn-lm.h
+//
+// Copyright (c)  2023  Pingfeng Luo
+// Copyright (c)  2023  Xiaomi Corporation
+
+#ifndef SHERPA_ONNX_CSRC_ONLINE_RNN_LM_H_
+#define SHERPA_ONNX_CSRC_ONLINE_RNN_LM_H_
+
+#include <memory>
+#include <utility>
+#include <vector>
+
+#include "onnxruntime_cxx_api.h"  // NOLINT
+#include "sherpa-onnx/csrc/online-lm-config.h"
+#include "sherpa-onnx/csrc/online-lm.h"
+
+namespace sherpa_onnx {
+
+class OnlineRnnLM : public OnlineLM {
+ public:
+  ~OnlineRnnLM() override;
+
+  explicit OnlineRnnLM(const OnlineLMConfig &config);
+
+  std::vector<Ort::Value> GetInitStates() override;
+
+  /** Rescore a batch of sentences.
+   *
+   * @param x A 2-D tensor of shape (N, L) with data type int64.
+   * @param y A 2-D tensor of shape (N, L) with data type int64.
+   * @param states It contains the states for the LM model
+   * @return Return a pair containingo
+   *          - negative loglike
+   *          - updated states
+   *
+   * Caution: It returns negative log likelihood (nll), not log likelihood
+   */
+  std::pair<Ort::Value, std::vector<Ort::Value>> Rescore(
+      Ort::Value x, Ort::Value y, std::vector<Ort::Value> states) override;
+
+ private:
+  class Impl;
+  std::unique_ptr<Impl> impl_;
+};
+
+}  // namespace sherpa_onnx
+
+#endif  // SHERPA_ONNX_CSRC_ONLINE_RNN_LM_H_