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Delaying the softmax() to avoid the pow()

Now at 5x real-time, with all the low-hanging fruit done.

--- a/dnn/nnet.c

+++ b/dnn/nnet.c

@@ -39,6 +39,8 @@

 #include "nnet.h"

 #include "nnet_data.h"

+#define SOFTMAX_HACK

+

 #ifdef __AVX2__

 #include <immintrin.h>

 static __m256 exp8_approx(__m256 X)

@@ -340,6 +342,10 @@

       for (i=0;i<N;i++)

          output[i] = relu(input[i]);

    } else if (activation == ACTIVATION_SOFTMAX) {

+#ifdef SOFTMAX_HACK

+      for (i=0;i<N;i++)

+         output[i] = input[i];

+#else

       float sum = 0;

       softmax(output, input, N);

       for (i=0;i<N;i++) {

@@ -348,6 +354,7 @@

       sum = 1.f/(sum+1e-30);

       for (i=0;i<N;i++)

          output[i] = sum*output[i];

+#endif

    } else {

       celt_assert(activation == ACTIVATION_LINEAR);

       for (i=0;i<N;i++)

@@ -619,6 +626,17 @@

     float tmp[DUAL_FC_OUT_SIZE];

     celt_assert(N <= DUAL_FC_OUT_SIZE);

     sum = 0;

+#ifdef SOFTMAX_HACK

+    for (i=0;i<N;i++)

+    {

+        tmp[i] = pdf[i] * (1.f+exp_boost);

+    }

+    softmax(tmp, tmp, N);

+    for (i=0;i<N;i++)

+    {

+        sum += tmp[i];

+    }

+#else

     /* Decrease the temperature of the sampling. */

     for (i=0;i<N;i++)

     {

@@ -625,6 +643,7 @@

         tmp[i] = pow(pdf[i], 1.f+exp_boost);

         sum += tmp[i];

     }

+#endif

     norm = 1.f/sum;

     /* Convert tmp to a CDF while subtracting the floor */

     tmp[0] = MAX16(0, norm*tmp[0] - pdf_floor);

-- 

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