add condition stop for kmeans

mindspore/lite/tools/converter/quantizer/quantize_util.cc

@@ -402,11 +402,13 @@ static std::vector<float> InitClusters(float *data, size_t elem_count, size_t k)
 std::vector<int8_t> KMeans(float *data, size_t elem_count, size_t k, size_t epochs, schema::QuantParamT *quantParam) {
   std::vector<float> clusters = InitClusters(data, elem_count, k);
   std::vector<int8_t> clusters_index{};
+  double error{0};
   if (clusters.size() < k) {
     MS_LOG(WARNING) << "K is less than the size of data so KMeans function is not executed.";
     return clusters_index;
   }
   for (size_t epoch = 0; epoch < epochs; epoch++) {
+    double error_cur{0};
     clusters_index.clear();
     std::vector<std::vector<float>> clusters_data(clusters.size());
     for (size_t i = 0; i < elem_count; i++) {
@@ -426,6 +428,15 @@ std::vector<int8_t> KMeans(float *data, size_t elem_count, size_t k, size_t epoc
         clusters[j] = std::accumulate(clusters_data[j].begin(), clusters_data[j].end(), 0.0) / clusters_data[j].size();
       }
     }
+    // compare error
+    for (size_t j = 0; j < elem_count; j++) {
+      error_cur += pow(data[j] - clusters[clusters_index[j]], 2);
+    }
+    error_cur = pow(error_cur / elem_count, 0.5);
+    if (std::abs((error_cur - error) / error_cur) < 1e-6) {
+      break;
+    }
+    error = error_cur;
   }
   // update data
   quantParam->clusters = clusters;