Transformer Engine v2.18 Release Notes

Key Features and Enhancements

• [Common] Added fused BF16 forward/backward kernels for scaled variants of SwiGLU, ClampedSwiGLU, and SReLU. (#3132)
• [Common] Reduced binary size and build time by migrating fused softmax, LayerNorm, and RMSNorm kernels to NVRTC. (#3156)
• [Common] Improved the performance of variable-length cuDNN fused attention forward passes by passing sequence-length metadata directly to cuDNN. (#3186)
• [Common, PyTorch] Added dense topk_indices output support to the fused router for TE Expert Parallelism. (#3129)
• [Common, PyTorch] Added FP8 current-scaling grouped quantization with support for varying tensor dimensions. (#3114)
• [Common, PyTorch] Made FP8 current scaling in GroupedLinear compatible with CUDA graph capture and improved cuBLASLt grouped GEMM algorithm selection. (#3143)
• [Common, PyTorch] Added CUDA graph capture support for THD attention. (#2898)
• [Common, JAX, PyTorch] Enabled cuDNN fused attention backward for attention head dimension 256 on Blackwell GPUs with compute capability 10.x. (#3056)
• [PyTorch] Enabled FP8 block scaling in GroupedLinear and fusible ops. (#3171) (#3242) (#3135)
• [PyTorch] Reduced scale-factor swizzling overhead for cached MXFP8 and NVFP4 weights. (#3093)
• [PyTorch] Added THD format support for AllGather-based context parallelism. (#2829)
• [PyTorch] Added zero-copy support to TE Expert Parallelism. (#3187)
• [PyTorch] Enabled NVFP4 RHT amax fusion in the grouped MLP using SRelu activation. (#3133)
• [PyTorch] Added NVTE_FLASH_ATTN_V2, NVTE_FLASH_ATTN_V3, and NVTE_FLASH_ATTN_V4 environment variables to control each FlashAttention version independently. (#3204)
• [JAX] Integrated the TE EP backend into the experimental moe() VJP API and experimental Flax MoEBlock. (#3116)
• [Docs] Improved the documentation on attention (#3142) (#3162)
• [Build] Replaced the cuDNN Frontend submodule with the nvidia-cudnn-frontend python package for source builds. (#3169) (#3278)

Fixed Issues

• [Common, PyTorch] Fixed grouped GEMM failures with FP8 per-tensor scaling on Hopper when using cuBLAS versions earlier than 13.5 by falling back to the legacy path. (#3181)
• [Common, PyTorch] Fixed CUDA graph failures with cached NVFP4 weights by producing GEMM-swizzled scaling factors during quantization when supported and disabling pre-swizzling otherwise. (#3190) (#3232)
• [PyTorch] Fixed gradient propagation for quantized tensors across autograd boundaries and made FP8 block-scaling dequantization autograd-aware. (#3172)
• [PyTorch] Fixed NVTE_BACKWARD_OVERRIDE=dequantized to use dequantized forward operands in backward. (#3141)
• [PyTorch] Fixed precision loss in the fused cross-entropy backward pass. (#3193)
• [PyTorch] Fixed process aborts during communication+GEMM overlap and NCCL-EP initialization caused by incorrect GIL handling. (#3203)
• [PyTorch] Fixed skipped updates in FusedAdam and FusedSGD when parameter groups contain empty tensors. (#3212)
• [PyTorch] Fixed NCCL communicator initialization when creating a cuSOLVERMp context. (#3240)
• [PyTorch] Fixed quantized tensor __repr__ failures when data cannot be materialized, including under torch.compile. (#3146)
• [JAX] Fixed the distributed MoE auxiliary loss backward pass by preserving the scalar cotangent. (#3237)
• [Build] Fixed a CUDA 13.0 source build failure in grouped FP8 quantization code. (#3194)

Known Issues in This Release

• There is a known compatibity issue between the FlashAttention v4, CuTeDSL and CUDNN Frontend pip packages, which could produce runtime errors like ImportError: cannot import name 'block_copy' from 'cutlass.utils'. A supported stable combination:
• flash-attn-4==4.0.0b11
• nvidia-cutlass-dsl[cu13]==4.4.2
• nvidia-cudnn-frontend==1.26.0

Breaking Changes in This Release

There are no breaking changes in this release.

Deprecated Features

There are no deprecated features in this release.