Root cause of cublasLtMatmul CUBLAS_STATUS_NOT_SUPPORTED:
- states_buf allocated [batch * state_dim] (unpadded)
- cuBLAS forward GEMM reads with stride state_dim_padded (pad128)
- Buffer overflow: GEMM reads past buffer end
cublasLtMatmul validates buffer sizes against layout descriptors and
returns NOT_SUPPORTED for undersized buffers. cublasSgemm silently
read garbage — this was the source of the "parallel test congestion
errors" seen previously.
Fix:
- Allocate states_buf with state_dim_padded stride (3 allocation sites)
- gather_states kernel: add padded_sd parameter, write with padded stride
- DtoD copy: use padded row bytes
- Both gather_states call sites updated with padded_sd arg
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
