Use 3d memory layout for pooling

src/kernels/pooling.cu

@@ -1,6 +1,5 @@
-#include "pooling.cuh"
-
 #include "cuda_helper.cuh"
+#include "pooling.cuh"
 
 using namespace CUDANet;
 
@@ -12,24 +11,20 @@ __global__ void Kernels::max_pooling(
     const int poolingSize,
     const int stride
 ) {
-    int tid = blockDim.x * blockIdx.x + threadIdx.x;
-    if (tid >= inputSize * inputSize * nChannels) {
+    int j = blockDim.x * blockIdx.x + threadIdx.x;
+    int i = blockDim.y * blockIdx.y + threadIdx.y;
+    int c = blockDim.z * blockIdx.z + threadIdx.z;
+
+    if (i >= inputSize || j >= inputSize || c >= nChannels) {
         return;
     }
 
-    // Get output index
-    int c = tid / (inputSize * inputSize);
-    int i = tid % (inputSize * inputSize) / inputSize;
-    int j = tid % inputSize;
-
     float max = 0.0f;
 
     for (int k = 0; k < poolingSize; k++) {
         for (int l = 0; l < poolingSize; l++) {
-
             int inputIndex = c * inputSize * inputSize +
-                             (i * stride + k) * inputSize +
-                             (j * stride + l);
+                             (i * stride + k) * inputSize + (j * stride + l);
 
             if (d_input[inputIndex] > max) {
                 max = d_input[inputIndex];
@@ -37,7 +32,7 @@ __global__ void Kernels::max_pooling(
         }
     }
 
-    d_output[tid] = max;
+    d_output[c * inputSize * inputSize + i * inputSize + j] = max;
 }
 
 __global__ void Kernels::avg_pooling(
@@ -48,28 +43,25 @@ __global__ void Kernels::avg_pooling(
     const int poolingSize,
     const int stride
 ) {
-    int tid = blockDim.x * blockIdx.x + threadIdx.x;
-    if (tid >= inputSize * inputSize * nChannels) {
+    int j = blockDim.x * blockIdx.x + threadIdx.x;
+    int i = blockDim.y * blockIdx.y + threadIdx.y;
+    int c = blockDim.z * blockIdx.z + threadIdx.z;
+
+    if (i >= inputSize || j >= inputSize || c >= nChannels) {
         return;
     }
 
-    // Get output index
-    int c = tid / (inputSize * inputSize);
-    int i = tid % (inputSize * inputSize) / inputSize;
-    int j = tid % inputSize;
-
     float sum = 0.0f;
 
     for (int k = 0; k < poolingSize; k++) {
         for (int l = 0; l < poolingSize; l++) {
-
             int inputIndex = c * inputSize * inputSize +
-                             (i * stride + k) * inputSize +
-                             (j * stride + l);
+                             (i * stride + k) * inputSize + (j * stride + l);
 
             sum += d_input[inputIndex];
         }
     }
 
-    d_output[tid] = sum / (poolingSize * poolingSize);
+    d_output[c * inputSize * inputSize + i * inputSize + j] =
+        sum / (poolingSize * poolingSize);
 }

src/layers/avg_pooling.cu

@@ -5,38 +5,44 @@
 using namespace CUDANet::Layers;
 
 AvgPooling2D::AvgPooling2D(
-        int            inputSize,
-        int            nChannels,
-        int            poolingSize,
-        int            stride,
-        ActivationType activationType
-    )
-    : inputSize(inputSize), nChannels(nChannels), poolingSize(poolingSize), stride(stride) {
+    int            inputSize,
+    int            nChannels,
+    int            poolingSize,
+    int            stride,
+    ActivationType activationType
+)
+    : inputSize(inputSize),
+      nChannels(nChannels),
+      poolingSize(poolingSize),
+      stride(stride) {
+    outputSize = (inputSize - poolingSize) / stride + 1;
 
-
-    outputSize  = (inputSize - poolingSize) / stride + 1;
-
-    activation = Activation(
-        activationType, outputSize * outputSize * nChannels
-    );
+    activation =
+        Activation(activationType, outputSize * outputSize * nChannels);
 
     d_output = nullptr;
     CUDA_CHECK(cudaMalloc(
         (void**)&d_output, sizeof(float) * outputSize * outputSize * nChannels
     ));
 
-    gridSize = (outputSize * outputSize * nChannels + BLOCK_SIZE - 1) / BLOCK_SIZE;
-
+    gridSize =
+        (outputSize * outputSize * nChannels + BLOCK_SIZE - 1) / BLOCK_SIZE;
 }
 
-
 AvgPooling2D::~AvgPooling2D() {
     cudaFree(d_output);
 }
 
-
 float* AvgPooling2D::forward(const float* d_input) {
-    Kernels::avg_pooling<<<gridSize, BLOCK_SIZE>>>(
+
+    dim3 block(8, 8, 8);
+    dim3 grid(
+        (outputSize + block.x - 1) / block.x,
+        (outputSize + block.y - 1) / block.y,
+        (nChannels + block.z - 1) / block.z
+    );
+
+    Kernels::avg_pooling<<<grid, block>>>(
         d_input, d_output, inputSize, nChannels, poolingSize, stride
     );
 

src/layers/max_pooling.cu

@@ -37,7 +37,15 @@ MaxPooling2D::~MaxPooling2D() {
 
 
 float* MaxPooling2D::forward(const float* d_input) {
-    Kernels::max_pooling<<<gridSize, BLOCK_SIZE>>>(
+
+    dim3 block(8,8,8);
+    dim3 grid(
+        (outputSize + block.x - 1) / block.x,
+        (outputSize + block.y - 1) / block.y,
+        (nChannels + block.z - 1) / block.z
+    );
+
+    Kernels::max_pooling<<<grid, block>>>(
         d_input, d_output, inputSize, nChannels, poolingSize, stride
     );