dsyequb - compute row and column scalings intended to equilibrate a symmetric matrix A and reduce its condition number with respect to the two-norm
SUBROUTINE DSYEQUB(UPLO, N, A, LDA, S, SCOND, AMAX, WORK, INFO) INTEGER INFO, LDA, N DOUBLE PRECISION AMAX, SCOND CHARACTER*1 UPLO DOUBLE PRECISION A(LDA,*), S(*), WORK(*) SUBROUTINE DSYEQUB_64(UPLO, N, A, LDA, S, SCOND, AMAX, WORK, INFO) INTEGER*8 INFO, LDA, N DOUBLE PRECISION AMAX, SCOND CHARACTER*1 UPLO DOUBLE PRECISION A(LDA,*), S(*), WORK(*) F95 INTERFACE SUBROUTINE SYEQUB(UPLO, N, A, LDA, S, SCOND, AMAX, WORK, INFO) INTEGER :: N, LDA, INFO CHARACTER(LEN=1) :: UPLO REAL(8), DIMENSION(:,:) :: A REAL(8), DIMENSION(:) :: S, WORK REAL(8) :: SCOND, AMAX SUBROUTINE SYEQUB_64(UPLO, N, A, LDA, S, SCOND, AMAX, WORK, INFO) INTEGER(8) :: N, LDA, INFO CHARACTER(LEN=1) :: UPLO REAL(8), DIMENSION(:,:) :: A REAL(8), DIMENSION(:) :: S, WORK REAL(8) :: SCOND, AMAX C INTERFACE #include <sunperf.h> void dsyequb (char uplo, int n, double *a, int lda, double *s, double *scond, double *amax, int *info); void dsyequb_64 (char uplo, long n, double *a, long lda, double *s, double *scond, double *amax, long *info);
Oracle Solaris Studio Performance Library dsyequb(3P) NAME dsyequb - compute row and column scalings intended to equilibrate a symmetric matrix A and reduce its condition number with respect to the two-norm SYNOPSIS SUBROUTINE DSYEQUB(UPLO, N, A, LDA, S, SCOND, AMAX, WORK, INFO) INTEGER INFO, LDA, N DOUBLE PRECISION AMAX, SCOND CHARACTER*1 UPLO DOUBLE PRECISION A(LDA,*), S(*), WORK(*) SUBROUTINE DSYEQUB_64(UPLO, N, A, LDA, S, SCOND, AMAX, WORK, INFO) INTEGER*8 INFO, LDA, N DOUBLE PRECISION AMAX, SCOND CHARACTER*1 UPLO DOUBLE PRECISION A(LDA,*), S(*), WORK(*) F95 INTERFACE SUBROUTINE SYEQUB(UPLO, N, A, LDA, S, SCOND, AMAX, WORK, INFO) INTEGER :: N, LDA, INFO CHARACTER(LEN=1) :: UPLO REAL(8), DIMENSION(:,:) :: A REAL(8), DIMENSION(:) :: S, WORK REAL(8) :: SCOND, AMAX SUBROUTINE SYEQUB_64(UPLO, N, A, LDA, S, SCOND, AMAX, WORK, INFO) INTEGER(8) :: N, LDA, INFO CHARACTER(LEN=1) :: UPLO REAL(8), DIMENSION(:,:) :: A REAL(8), DIMENSION(:) :: S, WORK REAL(8) :: SCOND, AMAX C INTERFACE #include <sunperf.h> void dsyequb (char uplo, int n, double *a, int lda, double *s, double *scond, double *amax, int *info); void dsyequb_64 (char uplo, long n, double *a, long lda, double *s, double *scond, double *amax, long *info); PURPOSE dsyequb computes row and column scalings intended to equilibrate a sym- metric matrix A and reduce its condition number (with respect to the two-norm). S contains the scale factors, S(i) = 1/sqrt(A(i,i)), chosen so that the scaled matrix B with elements B(i,j) = S(i)*A(i,j)*S(j) has ones on the diagonal. This choice of S puts the condition number of B within a factor N of the smallest possible condition number over all possible diagonal scalings. ARGUMENTS UPLO (input) UPLO is CHARACTER*1 Specifies whether the details of the factorization are stored as an upper or lower triangular matrix. = 'U': Upper triangular, form is A = U*D*U**T; = 'L': Lower triangular, form is A = L*D*L**T. N (input) N is INTEGER The order of the matrix A. N >= 0. A (input) A is DOUBLE PRECISION array, dimension (LDA,N) The N-by-N symmetric matrix whose scaling factors are to be computed. Only the diagonal elements of A are referenced. LDA (input) LDA is INTEGER The leading dimension of the array A. LDA >= max(1,N). S (output) S is DOUBLE PRECISION array, dimension (N) If INFO = 0, S contains the scale factors for A. SCOND (output) SCOND is DOUBLE PRECISION If INFO = 0, S contains the ratio of the smallest S(i) to the largest S(i). If SCOND >= 0.1 and AMAX is neither too large nor too small, it is not worth scaling by S. AMAX (output) AMAX is DOUBLE PRECISION Absolute value of largest matrix element. If AMAX is very close to overflow or very close to underflow, the matrix should be scaled. WORK (output) WORK is DOUBLE PRECISION array, dimension (3*N) INFO (output) INFO is INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value; > 0: if INFO = i, the i-th diagonal element is nonpositive. 7 Nov 2015 dsyequb(3P)