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cudaErrorMapBufferObjectFailed (205)cudaErrorMapBufferObjectFailed (error code 205) occurs when CUDA cannot map an OpenGL buffer object for access. This happens in CUDA-graphics interop scenarios where you share buffers between CUDA and OpenGL (or other graphics APIs). This error typically indicates that the graphics resource is not properly registered, is already mapped, or there's a context mismatch between CUDA and OpenGL. This guide covers CUDA-graphics interop troubleshooting for common scenarios.
CUDA error: failed to map buffer object cudaErrorMapBufferObjectFailed: failed to map buffer object CUDA_ERROR_MAP_FAILED cudaGraphicsMapResources failed
Register OpenGL buffer with CUDA before mapping.
// Step 1: Create OpenGL buffer
GLuint glBuffer;
glGenBuffers(1, &glBuffer);
glBindBuffer(GL_ARRAY_BUFFER, glBuffer);
glBufferData(GL_ARRAY_BUFFER, size, nullptr, GL_DYNAMIC_DRAW);
// Step 2: Register with CUDA (do once)
cudaGraphicsResource* cudaResource;
cudaGraphicsGLRegisterBuffer(&cudaResource, glBuffer, cudaGraphicsMapFlagsWriteDiscard);
// Now resource is ready for mappingFollow correct map/unmap sequence.
// Correct sequence:
// 1. Ensure OpenGL is not using the buffer
glBindBuffer(GL_ARRAY_BUFFER, 0); // Unbind from OpenGL
// 2. Map for CUDA
cudaGraphicsMapResources(1, &cudaResource, 0);
// 3. Get device pointer
float* d_ptr;
size_t size;
cudaGraphicsResourceGetMappedPointer((void**)&d_ptr, &size, cudaResource);
// 4. Use in CUDA kernel
kernel<<<grid, block>>>(d_ptr);
cudaDeviceSynchronize();
// 5. Unmap before OpenGL uses it
cudaGraphicsUnmapResources(1, &cudaResource, 0);
// 6. Now OpenGL can use buffer againEnsure resource is not already mapped.
// Track mapping state
bool isMapped = false;
void mapForCuda() {
if (isMapped) {
printf("Warning: Already mapped!\n");
return;
}
cudaError_t err = cudaGraphicsMapResources(1, &cudaResource, 0);
if (err == cudaSuccess) {
isMapped = true;
} else {
printf("Map failed: %s\n", cudaGetErrorString(err));
}
}
void unmapFromCuda() {
if (!isMapped) {
printf("Warning: Not mapped!\n");
return;
}
cudaGraphicsUnmapResources(1, &cudaResource, 0);
isMapped = false;
}OpenGL and CUDA must share proper context.
// Create OpenGL context first
glfwMakeContextCurrent(window);
// Then initialize CUDA on same device
int cudaDevice;
cudaGLGetDevices(&count, &cudaDevice, 1, cudaGLDeviceListCurrentFrame);
cudaSetDevice(cudaDevice);
// Verify contexts are compatible
printf("Using CUDA device %d for OpenGL interop\n", cudaDevice);
// When switching threads, ensure context is current
glfwMakeContextCurrent(window); // Make GL current
// Then CUDA operations workMapping already-mapped resource causes error.
// Map without checking state
cudaGraphicsMapResources(1, &res, 0);
kernel<<<g,b>>>(ptr);
cudaGraphicsMapResources(1, &res, 0); // Double map!Proper sequence with state tracking and synchronization.
void render_frame() {
// Ensure clean state
if (!resource_registered) {
cudaGraphicsGLRegisterBuffer(&res, glBuf, flags);
resource_registered = true;
}
// Unbind from GL
glBindBuffer(GL_ARRAY_BUFFER, 0);
// CUDA work
cudaGraphicsMapResources(1, &res, 0);
void* ptr; size_t size;
cudaGraphicsResourceGetMappedPointer(&ptr, &size, res);
kernel<<<g,b>>>(ptr);
cudaDeviceSynchronize();
cudaGraphicsUnmapResources(1, &res, 0);
// GL can use buffer now
glBindBuffer(GL_ARRAY_BUFFER, glBuf);
glDrawArrays(GL_POINTS, 0, count);
}Often a race condition - OpenGL still using buffer when CUDA tries to map. Always unbind from OpenGL and sync before mapping. Use glFinish() if needed.
No. CUDA-GL interop requires single-threaded access to each resource. Use proper synchronization between threads.
CUDA has separate Vulkan interop APIs (cudaExternalMemory). The OpenGL interop functions do not work with Vulkan.
Invalid resource handle
Context issues affect interop
Using unmapped pointer
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