nlpodyssey/spago

// Copyright ©2017 The Gonum Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

//go:build !amd64 || noasm || gccgo || safe
// +build !amd64 noasm gccgo safe

package asm32

// Ger performs the rank-one operation
//
//    A += alpha * x * yᵀ
//
// where A is an m×n dense matrix, x and y are vectors, and alpha is a scalar.
func Ger(m, n uintptr, alpha float32, x []float32, incX uintptr, y []float32, incY uintptr, a []float32, lda uintptr) {

    if incX == 1 && incY == 1 {
        x = x[:m]
        y = y[:n]
        for i, xv := range x {
            AxpyUnitary(alpha*xv, y, a[uintptr(i)*lda:uintptr(i)*lda+n])
        }
        return
    }

    var ky, kx uintptr
    if int(incY) < 0 {
        ky = uintptr(-int(n-1) * int(incY))
    }
    if int(incX) < 0 {
        kx = uintptr(-int(m-1) * int(incX))
    }

    ix := kx
    for i := 0; i < int(m); i++ {
        AxpyInc(alpha*x[ix], y, a[uintptr(i)*lda:uintptr(i)*lda+n], n, incY, 1, ky, 0)
        ix += incX
    }
}