82. Apple Metal: mount and forward

Part: XII · Apple acceleration (welvet.metal)
Package: nativemetal
Status: ok: verified macOS/arm64 on Apple M5

When

Mount a Go layer and execute its forward pass on Apple GPU.

Where

From example/welvet/82-apple-metal:

go run .
go run . -library /path/to/libwelvet_metal.dylib

Why

See the backend version and actual Metal device identity; release the session explicitly.

What

Creates an identity Dense layer, mounts it, forwards a Float32 tensor, and closes the session.

Requirements

Apple silicon macOS, Go with cgo, and the installed independent Metal dylib. Set WELVET_METAL_LIBRARY or install it from the Metal checkout:

cd /Users/openfluke/gs/welvet.metal
./scripts/macos_install_go.sh

Use the Go v1.3.0 checkout containing nativemetal. Examples 82-86 can also use go run -tags welvet_metal . to exclude the independent C++ binding. Example 87 needs the normal build to keep both native backends. Unsupported operating systems print SKIP. Missing libraries on a supported host report an error.

These are usage examples with small shapes. For speed measurements, use ../apple_stress_test. The results are numerical CPU/GPU comparisons, not model prediction accuracy.

Backend labels in routed examples: cpu-tiled is Go CPU, native_cpu is welvet.cpp, and metal is the independent Apple GPU backend.

Captured sample

backend=metal version=0.68
device=metal:Apple M5:reg=4294968322:ws=19069665280
input=[0.5 -0.25] output=[0.5 -0.25] shape=[1 2]

// Mount one layer, execute its forward pass on Apple Metal, and release it.
package main

import (
	"flag"
	"fmt"
	"github.com/openfluke/welvet/core"
	"github.com/openfluke/welvet/layers/dense"
	"github.com/openfluke/welvet/nativemetal"
	"github.com/openfluke/welvet/quant"
	"log"
	"runtime"
)

func main() {
	if e := run(); e != nil {
		log.Fatal(e)
	}
}
func run() error {
	library := flag.String("library", "", "optional libwelvet_metal.dylib path")
	flag.Parse()
	if runtime.GOOS != "darwin" || runtime.GOARCH != "arm64" {
		fmt.Println("SKIP: Apple Metal needs Apple silicon macOS and cgo")
		return nil
	}
	l, e := dense.NewConfigured(2, 2, core.ActivationLinear, core.DTypeFloat32, quant.FormatNone, []float32{1, 0, 0, 1})
	if e != nil {
		return e
	}
	session, e := nativemetal.Mount(l, nativemetal.Options{LibraryPath: *library})
	if e != nil {
		return e
	}
	defer session.Close()
	x := &core.Tensor[float32]{Shape: []int{1, 2}, Data: []float32{.5, -.25}}
	post, e := session.Forward(x)
	if e != nil {
		return e
	}
	fmt.Printf("backend=metal version=%s\ndevice=%s\ninput=%v output=%v shape=%v\n", session.Version(), session.Identity(), x.Data, post.Data, post.Shape)
	return nil
}