From 0f1a31648c5292fa49b35eac90a2ee676d6c13e6 Mon Sep 17 00:00:00 2001
From: Joseph Redmon <pjreddie@gmail.com>
Date: Sat, 31 Jan 2015 06:05:23 +0000
Subject: [PATCH] idk, probably something changed

---
 src/dropout_layer.c |   31 +++++++++++++++++++++++++------
 1 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/src/dropout_layer.c b/src/dropout_layer.c
index fcad7b9..3a3e4cb 100644
--- a/src/dropout_layer.c
+++ b/src/dropout_layer.c
@@ -1,6 +1,8 @@
 #include "dropout_layer.h"
-#include "stdlib.h"
-#include "stdio.h"
+#include "utils.h"
+#include "cuda.h"
+#include <stdlib.h>
+#include <stdio.h>
 
 dropout_layer *make_dropout_layer(int batch, int inputs, float probability)
 {
@@ -9,6 +11,13 @@
     layer->probability = probability;
     layer->inputs = inputs;
     layer->batch = batch;
+    layer->output = calloc(inputs*batch, sizeof(float));
+    layer->rand = calloc(inputs*batch, sizeof(float));
+    layer->scale = 1./(1.-probability);
+    #ifdef GPU
+    layer->output_gpu = cuda_make_array(layer->output, inputs*batch);
+    layer->rand_gpu = cuda_make_array(layer->rand, inputs*batch);
+    #endif
     return layer;
 } 
 
@@ -16,11 +25,21 @@
 {
     int i;
     for(i = 0; i < layer.batch * layer.inputs; ++i){
-        if((float)rand()/RAND_MAX < layer.probability) input[i] = 0;
-        else input[i] /= (1-layer.probability);
+        float r = rand_uniform();
+        layer.rand[i] = r;
+        if(r < layer.probability) layer.output[i] = 0;
+        else layer.output[i] = input[i]*layer.scale;
     }
 }
-void backward_dropout_layer(dropout_layer layer, float *input, float *delta)
+
+void backward_dropout_layer(dropout_layer layer, float *delta)
 {
-    // Don't do shit LULZ
+    int i;
+    if(!delta) return;
+    for(i = 0; i < layer.batch * layer.inputs; ++i){
+        float r = layer.rand[i];
+        if(r < layer.probability) delta[i] = 0;
+        else delta[i] *= layer.scale;
+    }
 }
+

--
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