1 SUBROUTINE DLASET( UPLO, M, N, ALPHA, BETA, A, LDA ) 2* 3* -- LAPACK auxiliary routine (version 3.0) -- 4* Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., 5* Courant Institute, Argonne National Lab, and Rice University 6* October 31, 1992 7* 8* .. Scalar Arguments .. 9 CHARACTER UPLO 10 INTEGER LDA, M, N 11 DOUBLE PRECISION ALPHA, BETA 12* .. 13* .. Array Arguments .. 14 DOUBLE PRECISION A( LDA, * ) 15* .. 16* 17* Purpose 18* ======= 19* 20* DLASET initializes an m-by-n matrix A to BETA on the diagonal and 21* ALPHA on the offdiagonals. 22* 23* Arguments 24* ========= 25* 26* UPLO (input) CHARACTER*1 27* Specifies the part of the matrix A to be set. 28* = 'U': Upper triangular part is set; the strictly lower 29* triangular part of A is not changed. 30* = 'L': Lower triangular part is set; the strictly upper 31* triangular part of A is not changed. 32* Otherwise: All of the matrix A is set. 33* 34* M (input) INTEGER 35* The number of rows of the matrix A. M >= 0. 36* 37* N (input) INTEGER 38* The number of columns of the matrix A. N >= 0. 39* 40* ALPHA (input) DOUBLE PRECISION 41* The constant to which the offdiagonal elements are to be set. 42* 43* BETA (input) DOUBLE PRECISION 44* The constant to which the diagonal elements are to be set. 45* 46* A (input/output) DOUBLE PRECISION array, dimension (LDA,N) 47* On exit, the leading m-by-n submatrix of A is set as follows: 48* 49* if UPLO = 'U', A(i,j) = ALPHA, 1<=i<=j-1, 1<=j<=n, 50* if UPLO = 'L', A(i,j) = ALPHA, j+1<=i<=m, 1<=j<=n, 51* otherwise, A(i,j) = ALPHA, 1<=i<=m, 1<=j<=n, i.ne.j, 52* 53* and, for all UPLO, A(i,i) = BETA, 1<=i<=min(m,n). 54* 55* LDA (input) INTEGER 56* The leading dimension of the array A. LDA >= max(1,M). 57* 58* ===================================================================== 59* 60* .. Local Scalars .. 61 INTEGER I, J 62* .. 63* .. External Functions .. 64 LOGICAL LSAME 65 EXTERNAL LSAME 66* .. 67* .. Intrinsic Functions .. 68 INTRINSIC MIN 69* .. 70* .. Executable Statements .. 71* 72 IF( LSAME( UPLO, 'U' ) ) THEN 73* 74* Set the strictly upper triangular or trapezoidal part of the 75* array to ALPHA. 76* 77 DO 20 J = 2, N 78 DO 10 I = 1, MIN( J-1, M ) 79 A( I, J ) = ALPHA 80 10 CONTINUE 81 20 CONTINUE 82* 83 ELSE IF( LSAME( UPLO, 'L' ) ) THEN 84* 85* Set the strictly lower triangular or trapezoidal part of the 86* array to ALPHA. 87* 88 DO 40 J = 1, MIN( M, N ) 89 DO 30 I = J + 1, M 90 A( I, J ) = ALPHA 91 30 CONTINUE 92 40 CONTINUE 93* 94 ELSE 95* 96* Set the leading m-by-n submatrix to ALPHA. 97* 98 DO 60 J = 1, N 99 DO 50 I = 1, M 100 A( I, J ) = ALPHA 101 50 CONTINUE 102 60 CONTINUE 103 END IF 104* 105* Set the first min(M,N) diagonal elements to BETA. 106* 107 DO 70 I = 1, MIN( M, N ) 108 A( I, I ) = BETA 109 70 CONTINUE 110* 111 RETURN 112* 113* End of DLASET 114* 115 END 116