Hi,
I have a GLSL compute shader, using some SSBO buffers, but I struggle to retrieve the content of a buffer, because of data alignments. It’s to update a neural network layer, for an opensource project (very early development though). Any help will be appreciate.
Here the GLSL parts (the sizes of the arrays may vary, here size 10 is for example):
struct Neighbor {
bool is_used;
uint index_x;
uint index_y;
vec4 weight; // weight of the neighbor connection
};
struct HiddenNeuron {
uint index_x;
uint index_y;
vec4 weights[10][10];
Neighbor neighbors[4];
};
layout(std430, binding = 3) buffer HiddenLayer1 {
HiddenNeuron neurons[10][10];
vec4 values[10][10];
vec4 errors[10][10];
float activation_alpha;
uint activation_function;
uint size_x;
uint size_y;
}
hiddenLayer1Buffer;
And here how I try to get the data for now, but something goes wrong with aberrant data, so I guess it’s an alignment issue.
builder_.mapBufferMemory(bufferHiddenLayer);
uint8_t *bufferData = reinterpret_cast<uint8_t *>(bufferHiddenLayer.data);
uint offset = 0;
// Read neurons
for (size_t y = 0; y < hiddenLayer->size_y; ++y) {
for (size_t x = 0; x < hiddenLayer->size_x; ++x) {
auto &dstNeuron = hiddenLayer->neurons[y][x];
// check index_x and index_y
uint index_x = 0;
std::memcpy(&index_x, bufferData + offset, sizeof(uint32_t));
offset += sizeof(uint32_t);
uint index_y = 0;
std::memcpy(&index_y, bufferData + offset, sizeof(uint32_t));
offset += sizeof(uint32_t);
if (dstNeuron.index_x != index_x || dstNeuron.index_y != index_y) {
throw VulkanControllerException("Invalid data buffer memory");
}
// get weights
for (int i = 0; i < dstNeuron.weights.rows; ++i) {
for (int j = 0; j < dstNeuron.weights.cols; ++j) {
for (int k = 0; k < 4; ++k) {
float value = 0.0f;
std::memcpy(&value, bufferData + offset, sizeof(float));
offset += sizeof(float);
dstNeuron.weights.at<cv::Vec4f>(i, j)[k] = value;
}
}
}
// get neighbors
for (int i = 0; i < MAX_NEIGHBORS; i++) {
bool isUsed = false;
std::memcpy(&isUsed, bufferData + offset, sizeof(uint32_t));
offset += sizeof(uint32_t);
uint index_x = 0;
std::memcpy(&index_x, bufferData + offset, sizeof(uint32_t));
offset += sizeof(uint32_t);
uint index_y = 0;
std::memcpy(&index_y, bufferData + offset, sizeof(uint32_t));
offset += sizeof(uint32_t);
for (int k = 0; k < 4; k++) {
float w = 0.0f;
std::memcpy(&w, bufferData + offset, sizeof(float));
offset += sizeof(float);
if (isUsed) {
dstNeuron.neighbors[i].weight[k] = w;
}
}
}
}
builder_.unmapBufferMemory(bufferHiddenLayer);
Regards,
