b12079

Add nccl support for multi-node tensor parallelism (#28967)

• Add a backend interface for collectives across ranks running in separate processes, implement it in the CUDA backend using NCCL, and use it in the RPC server when available.

• Drop ggml_backend_comm_allreduce_rank_t and reuse ggml_backend_comm_allreduce_tensor for per-rank communicators

• reuse ggml_backend_cuda_comm_allreduce_nccl for per-rank communicators. Remove the helper function backend_comm_proc_address

• Change ggml_backend_comm_get_unique_id_t and ggml_backend_comm_init_rank_t to more generic multi-process backend communicator interfaces

• set maxCTAs in ncclConfig_t to 8 for dgx spark in ggml_backend_cuda_comm_init_rank

Website:

• https://llama.app

Attestations:

• https://github.com/ggml-org/llama.cpp/attestations/63316073

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 26.04 s390x (CPU)
• Ubuntu 26.04 s390x (zDNN)
• Ubuntu x64 (Vulkan)
• Ubuntu arm64 (Vulkan)
• Ubuntu x64 (CUDA 12) - CUDA 12.8 libraries
• Ubuntu x64 (CUDA 13) - CUDA 13.4 libraries
• Ubuntu arm64 (CUDA 13) - CUDA 13.4 libraries
• Ubuntu x64 (ROCm 10.0)
• Ubuntu x64 (OpenVINO)
• Ubuntu x64 (SYCL FP32)
• Ubuntu x64 (SYCL FP16)
• Linux arm64 (Snapdragon: CPU, Adreno GPU, Hexagon NPU) - setup guide

Android:

• Android arm64 (CPU)
• Android arm64 (Snapdragon: CPU, Adreno GPU, Hexagon NPU) - setup guide

Windows:

• Windows x64 (CPU)
• Windows arm64 (CPU)
• Windows arm64 (OpenCL Adreno)
• Windows x64 (CUDA 12) - CUDA 12.4 DLLs
• Windows x64 (CUDA 13) - CUDA 13.4 DLLs
• Windows arm64 (CUDA 13) - CUDA 13.4 DLLs
• Windows x64 (Vulkan)
• Windows arm64 (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