Environment:Ggml org Llama cpp Metal GPU Environment

Knowledge Sources	llama.cpp Build Documentation
Domains	Infrastructure, GPU_Acceleration
Last Updated	2026-02-14 22:00 GMT

Overview

Apple Metal GPU acceleration environment for macOS, iOS, tvOS, and visionOS requiring the Metal framework and Apple Silicon or discrete AMD GPU.

Description

This environment enables GPU-accelerated inference on Apple platforms using the Metal compute shading API. Metal is the default and recommended backend for macOS builds. It automatically leverages the unified memory architecture of Apple Silicon chips (M1/M2/M3/M4), allowing models to use both CPU and GPU memory seamlessly. Metal shaders are embedded in the library at build time by default.

Usage

Use this environment for GPU-accelerated inference on Apple hardware. Metal is enabled by default when building on macOS (GGML_METAL=ON). No additional flags are needed for standard builds. Required for all inference workflows when running on Apple Silicon.

System Requirements

Category	Requirement	Notes
OS	macOS, iOS, tvOS, visionOS	Metal API required
Hardware	Apple Silicon (M1+) or AMD GPU	Apple Silicon uses unified memory
Frameworks	Foundation, Metal, MetalKit	Auto-linked by CMake
Disk	~200 MB	For compiled Metal shaders and binaries

Dependencies

System Packages

Xcode Command Line Tools (provides Metal compiler)
cmake >= 3.14
macOS SDK with Metal framework support

Credentials

No credentials are required.

Quick Install

# Metal is auto-enabled on macOS; standard build is sufficient
cmake -B build
cmake --build build --config Release -j $(sysctl -n hw.logicalcpu)

# Explicit Metal flags (for custom configurations)
cmake -B build -DGGML_METAL=ON -DGGML_METAL_EMBED_LIBRARY=ON
cmake --build build --config Release -j $(sysctl -n hw.logicalcpu)

Code Evidence

Metal auto-detection from ggml/CMakeLists.txt:

if (APPLE)
    option(GGML_METAL "ggml: use Metal" ON)
else()
    option(GGML_METAL "ggml: use Metal" OFF)
endif()

Framework linking from ggml/src/ggml-metal/CMakeLists.txt:

find_library(FOUNDATION_LIBRARY Foundation REQUIRED)
find_library(METAL_LIBRARY       Metal      REQUIRED)
find_library(METALKIT_LIBRARY    MetalKit   REQUIRED)
target_link_libraries(ggml-metal PRIVATE
    ${FOUNDATION_LIBRARY} ${METAL_LIBRARY} ${METALKIT_LIBRARY})

Metal build options from ggml/src/ggml-metal/CMakeLists.txt:

option(GGML_METAL_NDEBUG        "ggml: disable Metal debugging"        OFF)
option(GGML_METAL_SHADER_DEBUG  "ggml: compile with -fno-fast-math"    OFF)
option(GGML_METAL_EMBED_LIBRARY "ggml: embed Metal library in binary"  ${GGML_METAL})

Common Errors

Error Message	Cause	Solution
`Could NOT find Metal`	Not building on macOS or Xcode tools missing	Install Xcode Command Line Tools: `xcode-select --install`
`Metal library not found`	Embedded Metal library build failed	Rebuild with `-DGGML_METAL_EMBED_LIBRARY=ON`
`Unsupported OS for Metal`	Trying to enable Metal on Linux/Windows	Metal is Apple-only; use CUDA or Vulkan on other platforms

Compatibility Notes

Apple Silicon (M1/M2/M3/M4): Unified memory allows models to exceed GPU VRAM since CPU and GPU share the same memory pool.
Accelerate Framework: Automatically linked on macOS for BLAS operations (GGML_ACCELERATE=ON by default).
Shader Debugging: Enable GGML_METAL_SHADER_DEBUG to compile Metal shaders with -fno-fast-math for debugging numerical issues.
iOS/tvOS/visionOS: Supported via XCFramework builds. Use build-xcframework.sh script.

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