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// Copyright ©2015 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.
package gonum
import "gonum.org/v1/gonum/blas"
// Dlaset sets the off-diagonal elements of A to alpha, and the diagonal
// elements to beta. If uplo == blas.Upper, only the elements in the upper
// triangular part are set. If uplo == blas.Lower, only the elements in the
// lower triangular part are set. If uplo is otherwise, all of the elements of A
// are set.
//
// Dlaset is an internal routine. It is exported for testing purposes.
func (impl Implementation) Dlaset(uplo blas.Uplo, m, n int, alpha, beta float64, a []float64, lda int) {
switch {
case m < 0:
panic(mLT0)
case n < 0:
panic(nLT0)
case lda < max(1, n):
panic(badLdA)
}
minmn := min(m, n)
if minmn == 0 {
return
}
if len(a) < (m-1)*lda+n {
panic(shortA)
}
switch uplo {
case blas.Upper:
for i := 0; i < m; i++ {
for j := i + 1; j < n; j++ {
a[i*lda+j] = alpha
}
}
case blas.Lower:
for i := 0; i < m; i++ {
for j := 0; j < min(i, n); j++ {
a[i*lda+j] = alpha
}
}
default:
for i := 0; i < m; i++ {
for j := 0; j < n; j++ {
a[i*lda+j] = alpha
}
}
}
for i := 0; i < minmn; i++ {
a[i*lda+i] = beta
}
}