tor-browser

ml.c (6423B)

---

/*
* Copyright (c) 2016, Alliance for Open Media. All rights reserved.
*
* This source code is subject to the terms of the BSD 2 Clause License and
* the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
* was not distributed with this source code in the LICENSE file, you can
* obtain it at www.aomedia.org/license/software. If the Alliance for Open
* Media Patent License 1.0 was not distributed with this source code in the
* PATENTS file, you can obtain it at www.aomedia.org/license/patent.
*/

#include <assert.h>
#include <math.h>

#include "aom_dsp/aom_dsp_common.h"
#include "aom_dsp/mathutils.h"
#include "av1/encoder/ml.h"

void av1_nn_output_prec_reduce(float *const output, int num_output) {
 const int prec_bits = 9;
 const int prec = 1 << prec_bits;
 const float inv_prec = (float)(1.0 / prec);
 for (int i = 0; i < num_output; i++) {
   output[i] = ((int)(output[i] * prec + 0.5)) * inv_prec;
 }
}

// Calculate prediction based on the given input features and neural net config.
// Assume there are no more than NN_MAX_NODES_PER_LAYER nodes in each hidden
// layer.
void av1_nn_predict_c(const float *input_nodes,
                     const NN_CONFIG *const nn_config, int reduce_prec,
                     float *const output) {
 int num_input_nodes = nn_config->num_inputs;
 int buf_index = 0;
 float buf[2][NN_MAX_NODES_PER_LAYER];

 // Propagate hidden layers.
 const int num_layers = nn_config->num_hidden_layers;
 assert(num_layers <= NN_MAX_HIDDEN_LAYERS);
 for (int layer = 0; layer < num_layers; ++layer) {
   const float *layer_weights = nn_config->weights[layer];
   const float *layer_bias = nn_config->bias[layer];
   float *output_nodes = buf[buf_index];
   const int num_output_nodes = nn_config->num_hidden_nodes[layer];
   assert(num_output_nodes < NN_MAX_NODES_PER_LAYER);
   for (int node = 0; node < num_output_nodes; ++node) {
     float val = layer_bias[node];
     for (int i = 0; i < num_input_nodes; ++i)
       val += layer_weights[node * num_input_nodes + i] * input_nodes[i];
     // ReLU as activation function.
     val = val > 0.0f ? val : 0.0f;  // Could use AOMMAX().
     output_nodes[node] = val;
   }
   num_input_nodes = num_output_nodes;
   input_nodes = output_nodes;
   buf_index = 1 - buf_index;
 }

 // Final output layer.
 const float *layer_weights = nn_config->weights[num_layers];
 const float *layer_bias = nn_config->bias[num_layers];
 for (int node = 0; node < nn_config->num_outputs; ++node) {
   float val = layer_bias[node];
   for (int i = 0; i < num_input_nodes; ++i)
     val += layer_weights[node * num_input_nodes + i] * input_nodes[i];
   output[node] = val;
 }
 if (reduce_prec) av1_nn_output_prec_reduce(output, nn_config->num_outputs);
}

#if CONFIG_NN_V2
// Applies the ReLu activation to one fc layer
// output[i] = Max(input[i],0.0f)
static float *nn_relu(const float *input, FC_LAYER *layer) {
 for (int i = 0; i < layer->num_outputs; ++i) {
   layer->output[i] = AOMMAX(input[i], 0.0f);
 }

 return layer->output;
}

// Applies the Sigmoid activation to one fc layer
// output[i] = 1/(1+exp(input[i]))
static float *nn_sigmoid(const float *input, FC_LAYER *layer) {
 for (int i = 0; i < layer->num_outputs; ++i) {
   const float tmp = AOMMIN(AOMMAX(input[i], -10.0f), 10.0f);
   layer->output[i] = 1.0f / (1.0f + expf(-tmp));
 }

 return layer->output;
}

// Forward prediction in one fc layer, used in function av1_nn_predict_V2
static float *nn_fc_forward(const float *input, FC_LAYER *layer) {
 const float *weights = layer->weights;
 const float *bias = layer->bias;
 assert(layer->num_outputs < NN_MAX_NODES_PER_LAYER);
 // fc
 for (int node = 0; node < layer->num_outputs; ++node) {
   float val = bias[node];
   for (int i = 0; i < layer->num_inputs; ++i) val += weights[i] * input[i];
   layer->output[node] = val;
   weights += layer->num_inputs;
 }

 // activation
 switch (layer->activation) {
   case NONE: return layer->output;
   case RELU: return nn_relu(layer->output, layer);
   case SIGMOID: return nn_sigmoid(layer->output, layer);
   case SOFTSIGN:
     assert(0 && "Softsign has not been supported in NN.");  // TO DO
     return NULL;
   default:
     assert(0 && "Unknown activation");  // Unknown activation
     return NULL;
 }
}

void av1_nn_predict_v2(const float *feature, NN_CONFIG_V2 *nn_config,
                      int reduce_prec, float *output) {
 const float *input_nodes = feature;

 // Propagate the layers.
 const int num_layers = nn_config->num_hidden_layers;
 assert(num_layers <= NN_MAX_HIDDEN_LAYERS);
 for (int i = 0; i < num_layers; ++i) {
   input_nodes = nn_fc_forward(input_nodes, nn_config->layer + i);
   assert(nn_config->layer[i + 1].num_inputs ==
          nn_config->layer[i].num_outputs);
 }

 // Final layer
 input_nodes = nn_fc_forward(input_nodes, nn_config->layer + num_layers);
 assert(nn_config->layer[num_layers].num_outputs == nn_config->num_logits);
 // Copy the final layer output
 memcpy(output, input_nodes, sizeof(*input_nodes) * nn_config->num_logits);
 if (reduce_prec) av1_nn_output_prec_reduce(output, nn_config->num_logits);
}
#endif  // CONFIG_NN_V2

void av1_nn_softmax(const float *input, float *output, int n) {
 // Softmax function is invariant to adding the same constant
 // to all input values, so we subtract the maximum input to avoid
 // possible overflow.
 float max_input = input[0];
 for (int i = 1; i < n; i++) max_input = AOMMAX(max_input, input[i]);
 float sum_out = 0.0f;
 for (int i = 0; i < n; i++) {
   // Clamp to range [-10.0, 0.0] to prevent FE_UNDERFLOW errors.
   const float normalized_input = AOMMAX(input[i] - max_input, -10.0f);
   output[i] = expf(normalized_input);
   sum_out += output[i];
 }
 for (int i = 0; i < n; i++) output[i] /= sum_out;
}

void av1_nn_fast_softmax_16_c(const float *input, float *output) {
 const int kNumClasses = 16;
 float max_input = input[0];
 for (int i = 1; i < kNumClasses; i++) max_input = AOMMAX(max_input, input[i]);
 float sum_out = 0.0f;
 for (int i = 0; i < kNumClasses; i++) {
   // Clamp to range [-10.0, 0.0] to prevent FE_UNDERFLOW errors.
   const float normalized_input = AOMMAX(input[i] - max_input, -10.0f);
   output[i] = approx_exp(normalized_input);
   sum_out += output[i];
 }
 for (int i = 0; i < kNumClasses; i++) output[i] /= sum_out;
}