b10891

vulkan: fall back to shared-memory reduction for dmmv on PowerVR (#28341) The Imagination proprietary Vulkan compiler returns VK_ERROR_UNKNOWN from vkCreateComputePipelines for every dequant mul_mat_vec shader built with the subgroup-only reduction that requires a subgroup size >= 16. That covers the k-quants, the i-quants, TQ2_0, MXFP4 and NVFP4. ggml rethrows, so the first generated token of any such model kills the process. Reproduced on a Pixel 11 Pro (PowerVR C-Series CXTP-48-1536 MC1, driver 1.662.3024, subgroup size 128, min 32, max 128). The failure is independent of subgroup size: 32, 64 and 128 all fail, as does dropping the full-subgroups flag and the required-subgroup-size pNext. The legacy quants, which use the plain subgroup reduction, compile and run fine. The shared-memory reduction variant compiles and matches the CPU reference for q2_K, q3_K, q4_K, q5_K and q6_K. The hybrid variant also compiles but costs 27% of token throughput (3.78 vs 5.20 t/s on Qwen3.5-2B-Q4_K_M). Website: https://llama.app Attestations: https://github.com/ggml-org/llama.cpp/attestations/46549009 macOS/iOS: macOS Apple Silicon (arm64) macOS Apple Silicon (arm64, KleidiAI enabled) DISABLED macOS Intel (x64) iOS XCFramework Linux: Ubuntu x64 (CPU) Ubuntu arm64 (CPU) Ubuntu s390x (CPU) Ubuntu x64 (Vulkan) Ubuntu arm64 (Vulkan) Ubuntu x64 (ROCm 10.0) Ubuntu x64 (OpenVINO) Ubuntu x64 (SYCL FP32) Ubuntu x64 (SYCL FP16) Android: Android arm64 (CPU) Windows: Windows x64 (CPU) Windows arm64 (CPU) Windows arm64 (OpenCL Adreno) Windows x64 (CUDA 12) - CUDA 12.4 DLLs Windows x64 (CUDA 13) - CUDA 13.3 DLLs Windows arm64 (CUDA 13) (preview) - CUDA 13.4 DLLs Windows x64 (Vulkan) Windows x64 (OpenVINO) Windows x64 (SYCL) Windows x64 (ROCm 10.0) openEuler: DISABLED openEuler x86 (310p) openEuler x86 (910b, ACL Graph) openEuler aarch64 (310p) openEuler aarch64 (910b, ACL Graph) UI: UI

Source: llama.cpp Releases | 2026-09-10

Related