From 956cfcaec993111426d91bcd61676b5fe0ebfd16 Mon Sep 17 00:00:00 2001
From: Joseph Redmon <pjreddie@gmail.com>
Date: Mon, 24 Feb 2014 21:02:53 +0000
Subject: [PATCH] Feature extraction using Imagenet

---
 src/softmax_layer.c |   33 +++++++++++++++++++++++++++------
 1 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/src/softmax_layer.c b/src/softmax_layer.c
index 28696b7..b6b7ff3 100644
--- a/src/softmax_layer.c
+++ b/src/softmax_layer.c
@@ -5,18 +5,19 @@
 
 softmax_layer *make_softmax_layer(int inputs)
 {
-    printf("Softmax Layer: %d inputs\n", inputs);
+    fprintf(stderr, "Softmax Layer: %d inputs\n", inputs);
     softmax_layer *layer = calloc(1, sizeof(softmax_layer));
     layer->inputs = inputs;
-    layer->output = calloc(inputs, sizeof(double));
-    layer->delta = calloc(inputs, sizeof(double));
+    layer->output = calloc(inputs, sizeof(float));
+    layer->delta = calloc(inputs, sizeof(float));
     return layer;
 }
 
-void forward_softmax_layer(const softmax_layer layer, double *input)
+/* UNSTABLE!
+void forward_softmax_layer(const softmax_layer layer, float *input)
 {
     int i;
-    double sum = 0;
+    float sum = 0;
     for(i = 0; i < layer.inputs; ++i){
         sum += exp(input[i]);
     }
@@ -24,8 +25,28 @@
         layer.output[i] = exp(input[i])/sum;
     }
 }
+*/
+void forward_softmax_layer(const softmax_layer layer, float *input)
+{
+    int i;
+    float sum = 0;
+    float largest = 0;
+    for(i = 0; i < layer.inputs; ++i){
+        if(input[i] > largest) largest = input[i];
+    }
+    for(i = 0; i < layer.inputs; ++i){
+        sum += exp(input[i]-largest);
+        //printf("%f, ", input[i]);
+    }
+    //printf("\n");
+    if(sum) sum = largest+log(sum);
+    else sum = largest-100;
+    for(i = 0; i < layer.inputs; ++i){
+        layer.output[i] = exp(input[i]-sum);
+    }
+}
 
-void backward_softmax_layer(const softmax_layer layer, double *input, double *delta)
+void backward_softmax_layer(const softmax_layer layer, float *input, float *delta)
 {
     int i;
     for(i = 0; i < layer.inputs; ++i){

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