Switch all 3 forward-pass cublasGemmEx calls from CUBLAS_COMPUTE_32F to
CUBLAS_COMPUTE_32F_FAST_TF32, enabling H100 TF32 tensor cores for 2-3x
throughput. Backward pass remains at full F32 precision for gradient stability.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>