cuda kernel_launch_error ai_generated true

CUDA error: invalid configuration argument (cudaErrorInvalidConfiguration) - too many threads per block

ID: cuda/too-many-threads

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92%Fix Rate
95%Confidence
50Evidence
2023-01-01First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
12 active — — —

Root Cause

Kernel launch requested more threads per block than the GPU supports (typically max 1024). Or block dimensions exceed per-dimension limits (1024 x 1024 x 64). Common when hardcoding block sizes without checking device capabilities.

generic

Workarounds

  1. 95% success Reduce block size to 256 or 512 and increase grid size to compensate 
    Use dim3 block(256) and dim3 grid((N + 255) / 256) instead of launching with >1024 threads
  2. 90% success Query device properties to set block size dynamically 
    cudaDeviceProp prop; cudaGetDeviceProperties(&prop, 0); use prop.maxThreadsPerBlock
  3. 88% success Use occupancy API to determine optimal block size 
    cudaOccupancyMaxPotentialBlockSize(&minGridSize, &blockSize, myKernel, 0, 0)

Dead Ends

Common approaches that don't work:

  1. Ignore the error and increase GPU memory allocation 95% fail

    Thread limits are hardware-imposed per SM, not related to memory. More memory does not allow more threads per block.

  2. Use cudaSetDevice to switch to a different GPU 90% fail

    All modern NVIDIA GPUs have the same max threads per block (1024); switching devices will not help

Error Chain

Leads to:
Frequently confused with: