improve perfomance by using blas-like ops (eg. faxpy/fma) for gru had…

…amard product

src/rnn.c

@@ -76,35 +76,38 @@ static OPUS_INLINE float relu(float x)
    return x < 0 ? 0 : x;
 }
 
+static void faxpy(float *restrict a, const rnn_weight *restrict b, int k, float u)
+{
+  if (u == 0.0) return;
+  for (int idx = 0; idx < k; idx++)
+    a[idx] += b[idx] * u;
+}
+
 void compute_dense(const DenseLayer *layer, float *output, const float *input)
 {
    int i, j;
    int N, M;
-   int stride;
    M = layer->nb_inputs;
    N = layer->nb_neurons;
-   stride = N;
-   for (i=0;i<N;i++)
-   {
-      /* Compute update gate. */
-      float sum = layer->bias[i];
-      for (j=0;j<M;j++)
-         sum += layer->input_weights[j*stride + i]*input[j];
-      output[i] = WEIGHTS_SCALE*sum;
-   }
+   const rnn_weight *ip = layer->input_weights;
+   /* Compute update gate. */
+   for(i = 0; i < N; i++)
+     output[i] = layer->bias[i];
+   for (j=0;j<M;j++,ip+=N)
+     faxpy(output, ip, N, input[j]);
    switch (layer->activation) {
      case ACTIVATION_SIGMOID:
       for (i=0;i<N;i++)
-         output[i] = sigmoid_approx(output[i]);
+         output[i] = sigmoid_approx(WEIGHTS_SCALE * output[i]);
       break;
     case ACTIVATION_TANH:
       for (i=0;i<N;i++)
-         output[i] = tansig_approx(output[i]);
+         output[i] = tansig_approx(WEIGHTS_SCALE * output[i]);
       break;
     default:
     case ACTIVATION_RELU:
       for (i=0;i<N;i++)
-         output[i] = relu(output[i]);
+         output[i] = relu(WEIGHTS_SCALE * output[i]);
       break;
    }
 }
@@ -120,44 +123,49 @@ void compute_gru(const GRULayer *gru, float *state, const float *input)
    M = gru->nb_inputs;
    N = gru->nb_neurons;
    stride = 3*N;
-   for (i=0;i<N;i++)
-   {
-      /* Compute update gate. */
-      float sum = gru->bias[i];
-      for (j=0;j<M;j++)
-         sum += gru->input_weights[j*stride + i]*input[j];
-      for (j=0;j<N;j++)
-         sum += gru->recurrent_weights[j*stride + i]*state[j];
-      z[i] = sigmoid_approx(WEIGHTS_SCALE*sum);
-   }
-   for (i=0;i<N;i++)
-   {
-      /* Compute reset gate. */
-      float sum = gru->bias[N + i];
-      for (j=0;j<M;j++)
-         sum += gru->input_weights[N + j*stride + i]*input[j];
-      for (j=0;j<N;j++)
-         sum += gru->recurrent_weights[N + j*stride + i]*state[j];
-      r[i] = sigmoid_approx(WEIGHTS_SCALE*sum);
+   const rnn_weight *ip = gru->input_weights;
+   const rnn_weight *rp = gru->recurrent_weights;
+   /* Compute update gate. */
+   for(i = 0; i < N; i++)
+     z[i] = gru->bias[i];
+   for (j=0;j<M;j++,ip+=stride)
+     faxpy(z, ip, N, input[j]);
+   for (j=0;j<N;j++,rp+=stride)
+     faxpy(z, rp, N, state[j]);
+   for(i = 0; i < N; i++)
+     z[i] = sigmoid_approx(WEIGHTS_SCALE*z[i]);
+   /* Compute reset gate. */
+   for(i = 0; i < N; i++)
+     r[i] = gru->bias[N+i];
+   ip = gru->input_weights + N;
+   rp = gru->recurrent_weights + N;
+   for (j=0;j<M;j++,ip+=stride)
+     faxpy(r, ip, N, input[j]);
+   for (j=0;j<N;j++,rp+=stride)
+     faxpy(r, rp, N, state[j]);
+   for(i = 0; i < N; i++)
+     r[i] = sigmoid_approx(WEIGHTS_SCALE*r[i]);
+
+   /* Compute output. */
+   for(i = 0; i < N; i++)
+     h[i] = gru->bias[2*N+i];
+   ip = gru->input_weights + 2*N;
+   rp = gru->recurrent_weights + 2*N;
+   for (j=0;j<M;j++,ip+=stride)
+     faxpy(h, ip, N, input[j]);
+   for (j=0;j<N;j++,rp+=stride)
+     faxpy(h, rp, N, r[j]*state[j]);
+   for (i=0;i<N;i++) {
+     switch (gru->activation) {
+       case ACTIVATION_SIGMOID: h[i] = sigmoid_approx(WEIGHTS_SCALE*h[i]);break;
+       case ACTIVATION_TANH: h[i] = tansig_approx(WEIGHTS_SCALE*h[i]); break;
+       default:
+       case  ACTIVATION_RELU: h[i] = relu(WEIGHTS_SCALE*h[i]); break;
+     }
+     h[i] = z[i]*state[i] + (1-z[i])*h[i];
    }
    for (i=0;i<N;i++)
-   {
-      /* Compute output. */
-      float sum = gru->bias[2*N + i];
-      for (j=0;j<M;j++)
-         sum += gru->input_weights[2*N + j*stride + i]*input[j];
-      for (j=0;j<N;j++)
-         sum += gru->recurrent_weights[2*N + j*stride + i]*state[j]*r[j];
-    switch (gru->activation) {
-      case ACTIVATION_SIGMOID: sum = sigmoid_approx(WEIGHTS_SCALE*sum);break;
-      case ACTIVATION_TANH: sum = tansig_approx(WEIGHTS_SCALE*sum); break;
-      default:
-      case  ACTIVATION_RELU: sum = relu(WEIGHTS_SCALE*sum); break;
-    }
-    h[i] = z[i]*state[i] + (1-z[i])*sum;
-  }
-  for (i=0;i<N;i++)
-    state[i] = h[i];
+       state[i] = h[i];
 }
 
 #define INPUT_SIZE 42