Refactor hotwords，support loading hotwords from file (#296)

sherpa-onnx/csrc/context-graph-test.cc

@@ -4,11 +4,14 @@
 
 #include "sherpa-onnx/csrc/context-graph.h"
 
+#include <chrono>  // NOLINT
 #include <map>
+#include <random>
 #include <string>
 #include <vector>
 
 #include "gtest/gtest.h"
+#include "sherpa-onnx/csrc/macros.h"
 
 namespace sherpa_onnx {
 
@@ -41,4 +44,29 @@ TEST(ContextGraph, TestBasic) {
   }
 }
 
+TEST(ContextGraph, Benchmark) {
+  std::random_device rd;
+  std::mt19937 mt(rd());
+  std::uniform_int_distribution<int32_t> char_dist(0, 25);
+  std::uniform_int_distribution<int32_t> len_dist(3, 8);
+  for (int32_t num = 10; num <= 10000; num *= 10) {
+    std::vector<std::vector<int32_t>> contexts;
+    for (int32_t i = 0; i < num; ++i) {
+      std::vector<int32_t> tmp;
+      int32_t word_len = len_dist(mt);
+      for (int32_t j = 0; j < word_len; ++j) {
+        tmp.push_back(char_dist(mt));
+      }
+      contexts.push_back(std::move(tmp));
+    }
+    auto start = std::chrono::high_resolution_clock::now();
+    auto context_graph = ContextGraph(contexts, 1);
+    auto stop = std::chrono::high_resolution_clock::now();
+    auto duration =
+        std::chrono::duration_cast<std::chrono::microseconds>(stop - start);
+    SHERPA_ONNX_LOGE("Construct context graph for %d item takes %ld us.", num,
+                     duration.count());
+  }
+}
+
 }  // namespace sherpa_onnx