A python wrapper for Apple's Metal API


Keywords
apple, gpu, gpu-acceleration, metal, python, wrapper
License
MIT
Install
pip install metalgpu==1.0.3

Documentation

Python application

Metal GPU

This is a simple python library, wrapping Apple's Metal API to run compute kernels from python, with full control over buffers and methods. No copying behind the scenes, and raw access to the buffers as numpy arrays

Installing

Running pip install metalgpu to download latest release. After the first install, you will need to compile the C library.

To do so, simply run in your terminal python -m metalgpu build, and let it build the library. This leaves no files behind, apart from the compiled library.

Alternatively, simply run pip install metalgpu && python -m metalgpu build

Note: You need to have the git command line to use this tool, otherwise manually compile the folder metal-gpu-c and move the output library to the lib folder

Examples

main.py

import metalgpu

instance = metalgpu.Interface()  # Initialise the metal instance
shader_string = """
#include <metal_stdlib>

using namespace metal;

kernel void adder(device int *arr1 [[buffer(0)]],
        device int *arr2 [[buffer(1)]],
        device int *arr3 [[buffer(2)]],
        uint id [[thread_position_in_grid]]) {
    arr3[id] = arr2[id] + arr1[id];
}
"""
# Note: For clearer code, use instance.load_shader(shaderPath) to load a metal file

instance.load_shader_from_string(shader_string)
instance.set_function("adder")

buffer_size = 100000  # Number of items in the buffer
buffer_type = "int"

initial_array = [i for i in range(buffer_size)]

buffer1 = instance.array_to_buffer(initial_array)
buffer2 = instance.array_to_buffer(initial_array)
buffer3 = instance.create_buffer(buffer_size, buffer_type)

instance.run_function(buffer_size, [buffer1, buffer2, buffer3])

assert(all(buffer3.contents == [i * 2 for i in range(buffer_size)]))

buffer1.release()
buffer2.release()
buffer3.release()

Performance

When tested using performance.py, on Apple Silicon M1 Pro, base specs:

Function CPU Compute Time GPU Compute Time
Calculating 10 million cos values 3.553s 0.0100s
Calculating 10 million square roots 3.737s 0.00694s

Note: The GPU compute is almost as fast computing 1 million or 10 calculations, being limited by throughput to about 0.001s minimum per function run.

Documentation

To view the documentation, simply go to the docs folder and view the docs.md file

Known issues

  • None :)

Credits

  • metalcpp The wrapper from Objective-C to Metal, that is used to interact with Metal
  • MyMetalKernel.py Didn't manage to get this to work, overcomplicated for python code
  • metalcompute Although similar, performs lots of array copies instead of buffer management, and has some memory leaks.