github.com/jingcheng-WU/gonum@v0.9.1-0.20210323123734-f1a2a11a8f7b/lapack/gonum/dlaset.go (about)

     1  // Copyright ©2015 The Gonum Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package gonum
     6  
     7  import "github.com/jingcheng-WU/gonum/blas"
     8  
     9  // Dlaset sets the off-diagonal elements of A to alpha, and the diagonal
    10  // elements to beta. If uplo == blas.Upper, only the elements in the upper
    11  // triangular part are set. If uplo == blas.Lower, only the elements in the
    12  // lower triangular part are set. If uplo is otherwise, all of the elements of A
    13  // are set.
    14  //
    15  // Dlaset is an internal routine. It is exported for testing purposes.
    16  func (impl Implementation) Dlaset(uplo blas.Uplo, m, n int, alpha, beta float64, a []float64, lda int) {
    17  	switch {
    18  	case m < 0:
    19  		panic(mLT0)
    20  	case n < 0:
    21  		panic(nLT0)
    22  	case lda < max(1, n):
    23  		panic(badLdA)
    24  	}
    25  
    26  	minmn := min(m, n)
    27  	if minmn == 0 {
    28  		return
    29  	}
    30  
    31  	if len(a) < (m-1)*lda+n {
    32  		panic(shortA)
    33  	}
    34  
    35  	switch uplo {
    36  	case blas.Upper:
    37  		for i := 0; i < m; i++ {
    38  			for j := i + 1; j < n; j++ {
    39  				a[i*lda+j] = alpha
    40  			}
    41  		}
    42  	case blas.Lower:
    43  		for i := 0; i < m; i++ {
    44  			for j := 0; j < min(i, n); j++ {
    45  				a[i*lda+j] = alpha
    46  			}
    47  		}
    48  	default:
    49  		for i := 0; i < m; i++ {
    50  			for j := 0; j < n; j++ {
    51  				a[i*lda+j] = alpha
    52  			}
    53  		}
    54  	}
    55  	for i := 0; i < minmn; i++ {
    56  		a[i*lda+i] = beta
    57  	}
    58  }