From: Brendan Hansen <brendan.f.hansen@gmail.com>
Date: Thu, 21 Jan 2021 21:50:23 +0000 (-0600)
Subject: basics of loading the training examples
X-Git-Url: https://git.brendanfh.com/?a=commitdiff_plain;h=58ece8d8c508ed3ef6a2d43af298d9aa57ebffcc;p=onyx-mnist.git

basics of loading the training examples
---

diff --git a/src/mnist.onyx b/src/mnist.onyx
index d1d817c..4fa73ec 100644
--- a/src/mnist.onyx
+++ b/src/mnist.onyx
@@ -10,16 +10,45 @@ use package core
 // Load the data
 // Feed forward neural net
 
+load_example :: (fs: ^io.FileStream, example: u32, out: [784] u8) {
+    location := 16 + example * 784;
+    _, bytes_read := io.stream_read_at(fs, location, ~~ out);
+    
+    assert(bytes_read == 784, "Incorrect number of bytes read.");
+}
+
 main :: (args: [] cstr) {
     // Enables a logging allocator to print every allocation
     // main_allocator := context.allocator;
     // context.allocator = alloc.log.logging_allocator(^main_allocator);
 
+    random.set_seed(1234);
+
+    err, training_example := io.open("data/train-images-idx3-ubyte");
+    if err != io.Error.None {
+        println("There was an error loading the file.");
+        return;
+    }
+    defer io.stream_close(^training_example);
+
+    example : [784] u8;
+    load_example(^training_example, 0, example);
+
     nn := make_neural_net(28 * 28, 1000, 10);
+    defer neural_net_free(^nn);
 
-    neural_net_forward(^nn, ~~ input);
+    input := memory.make_slice(f32, 784);
+    defer cfree(input.data);
+
+    // CLEANUP: The double cast that is necessary here is gross.
+    for i: input.count do input[i] = (cast(f32) cast(u32) example[i]) / 255;
 
+    neural_net_forward(^nn, ~~ input);
     output := neural_net_get_output(^nn);
 
     for o: output do println(o);
+
+    expected := f32.[ 0, 0, 0, 0, 0, 0, 0, 0, 1, 0 ];
+    loss := neural_net_loss(^nn, ~~ expected);
+    printf("MSE loss: %f\n", loss);
 }
\ No newline at end of file
diff --git a/src/neuralnet.onyx b/src/neuralnet.onyx
index 6ada2ef..e1cd81a 100644
--- a/src/neuralnet.onyx
+++ b/src/neuralnet.onyx
@@ -14,10 +14,10 @@ NeuralNet :: struct {
 make_neural_net :: (layer_sizes: ..i32) -> NeuralNet {
     net : NeuralNet;
 
-    net.layer_arena  = alloc.arena.make(alloc.heap_allocator, 64 * 1024 * 1024); // 64 MiB
+    net.layer_arena  = alloc.arena.make(context.allocator, 64 * 1024 * 1024); // 64 MiB
     layer_allocator := alloc.arena.make_allocator(^net.layer_arena);
 
-    net.layers = memory.make_slice(Layer, layer_sizes.count);
+    net.layers = memory.make_slice(Layer, layer_sizes.count, allocator = layer_allocator);
 
     init_layer(^net.layers[0], layer_sizes[0], 0, allocator = layer_allocator);
     for i: 1 .. net.layers.count {
@@ -27,6 +27,10 @@ make_neural_net :: (layer_sizes: ..i32) -> NeuralNet {
     return net;
 }
 
+neural_net_free :: (use nn: ^NeuralNet) {
+    alloc.arena.free(^layer_arena);
+}
+
 neural_net_forward :: (use nn: ^NeuralNet, input: [] float) {
     assert(input.count == layers[0].neurons.count, "Input does not have the same size as the first layer.");
 
@@ -37,14 +41,35 @@ neural_net_forward :: (use nn: ^NeuralNet, input: [] float) {
     }
 }
 
+neural_net_backward :: (use nn: ^NeuralNet, expected_output: [] float) {
+
+}
+
 neural_net_get_output :: (use nn: ^NeuralNet) -> [] float {
     return layers[layers.count - 1].neurons;
 }
 
+neural_net_loss :: (use nn: ^NeuralNet, expected_output: [] float) -> float {
+    // MSE loss
+    assert(layers[layers.count - 1].neurons.count == expected_output.count,
+            "Expected output does not have the same size as the last layer.");
+
+    output := layers[layers.count - 1].neurons;
+
+    squared_sum: float = 0;
+    for i: expected_output.count {
+        diff := output[i] - expected_output[i];
+        squared_sum += diff * diff;
+    }
+
+    loss := math.sqrt(squared_sum);
+    return loss;
+}
+
 
 Layer :: struct {
     neurons :   [] float;
-    weights : [][] float;
+    weights : [][] float; // CLEANUP: Make this a rank 1 slice
 }
 
 init_layer :: (use layer: ^Layer, layer_size: u32, prev_layer_size: u32, allocator := context.allocator) {
@@ -64,7 +89,7 @@ init_layer :: (use layer: ^Layer, layer_size: u32, prev_layer_size: u32, allocat
 randomize_weights :: (use layer: ^Layer) {
     for ^weight: weights {
         for ^w: *weight {
-            *w = random.float(-2.0f, 2.0f);
+            *w = random.float(-1.0f, 1.0f);
         }
     }
 }