gpu/gpu_cpu.go

//go:build !cgo

package gpu

import (
	"context"
	"fmt"
	"runtime"
)

// CPUDevice represents CPU-based computation fallback
type CPUDevice struct {
	numCores    int
	simdSupport string
}

// InitCPU initializes CPU-based computation
func InitCPU() (*CPUDevice, error) {
	return &CPUDevice{
		numCores:    runtime.NumCPU(),
		simdSupport: detectSIMD(),
	}, nil
}

// detectSIMD detects available SIMD instructions
func detectSIMD() string {
	// This would ideally check for AVX, AVX2, AVX512, NEON etc.
	// For now, return a placeholder
	switch runtime.GOARCH {
	case "amd64":
		return "AVX2"
	case "arm64":
		return "NEON"
	default:
		return "none"
	}
}

// MatMul performs matrix multiplication on CPU
func (d *CPUDevice) MatMul(a, b []float32, m, n, k int) ([]float32, error) {
	if len(a) != m*k || len(b) != k*n {
		return nil, fmt.Errorf("invalid matrix dimensions")
	}

	result := make([]float32, m*n)

	// Simple CPU implementation
	// TODO: Optimize with SIMD instructions
	for i := 0; i < m; i++ {
		for j := 0; j < n; j++ {
			sum := float32(0)
			for l := 0; l < k; l++ {
				sum += a[i*k+l] * b[l*n+j]
			}
			result[i*n+j] = sum
		}
	}

	return result, nil
}

// Add performs element-wise addition on CPU
func (d *CPUDevice) Add(a, b []float32) ([]float32, error) {
	if len(a) != len(b) {
		return nil, fmt.Errorf("arrays must have same length")
	}

	result := make([]float32, len(a))

	// Simple CPU implementation
	// TODO: Optimize with SIMD instructions
	for i := range a {
		result[i] = a[i] + b[i]
	}

	return result, nil
}

// cpuSessionHandle implements sessionHandle for CPU-only builds
type cpuSessionHandle struct{}

func (h *cpuSessionHandle) backend() Backend { return CPU }
func (h *cpuSessionHandle) device() Device {
	return Device{
		Type:   CPU,
		ID:     0,
		Name:   "CPU",
		Memory: 8 * 1024 * 1024 * 1024, // 8GB placeholder
	}
}
func (h *cpuSessionHandle) sync() error                         { return nil }
func (h *cpuSessionHandle) syncContext(_ context.Context) error { return nil }
func (h *cpuSessionHandle) close() error                        { return nil }
func (h *cpuSessionHandle) tensor() TensorOps                   { return nil }
func (h *cpuSessionHandle) crypto() CryptoOps                   { return nil }
func (h *cpuSessionHandle) fhe() FHEOps                         { return nil }
func (h *cpuSessionHandle) ml() MLOps                           { return nil }

// newSession creates a new session for CPU-only builds
func newSession(cfg *sessionConfig) (*Session, error) {
	handle := &cpuSessionHandle{}
	return &Session{
		handle:  handle,
		backend: CPU,
		device:  handle.device(),
	}, nil
}