how easy it is to use blas from go-lang

blas.go

// see http://www.netlib.org/clapack/cblas/dgemv.c
package main

/*
#cgo LDFLAGS: -L/usr/lib/libblas -lblas
#include <stdlib.h>
extern void dgemv_(char* trans, int *m, int *n, double *alpha,
    double *A, int *lda, double *x, int *incx, double *beta, double *y,
    int *incy);
*/
import "C"

import (
	"fmt"
	"unsafe"
)

/*

matrix-vector multiplication:

 [1, 3] * [ 5 ] = [ 23 ]
 [2, 4]   [ 6 ]   [ 34 ]

mra@desktop ~/Desktop $ go run blas.go
[23 34]

*/
func main() {
	a := []float64{1, 2, 3, 4}
	x := []float64{5, 6}
	y := make([]float64, 2)
	Dgemv("N", 2, 2, 1.0, a, 2, x, 1, 0.0, y, 1)
	fmt.Println(y)
}

func Dgemv(transA string, M int, N int, alpha float64,
	A []float64, lda int, X []float64, incX int, beta float64,
	Y []float64, incY int) {

	ctransA := C.CString(transA)
	defer C.free(unsafe.Pointer(ctransA))

	C.dgemv_(ctransA,
		(*C.int)(unsafe.Pointer(&M)),
		(*C.int)(unsafe.Pointer(&N)),
		(*C.double)(unsafe.Pointer(&alpha)),
		(*C.double)(unsafe.Pointer(&A[0])),
		(*C.int)(unsafe.Pointer(&lda)),
		(*C.double)(unsafe.Pointer(&X[0])),
		(*C.int)(unsafe.Pointer(&incX)),
		(*C.double)(unsafe.Pointer(&beta)),
		(*C.double)(unsafe.Pointer(&Y[0])),
		(*C.int)(unsafe.Pointer(&incY)))
}