dpoequ (3p)

Name

dpoequ - metric positive definite matrix A and reduce its condition number (with respect to the two-norm)

Synopsis

SUBROUTINE DPOEQU(N, A, LDA, SCALE, SCOND, AMAX, INFO)

INTEGER N, LDA, INFO
DOUBLE PRECISION SCOND, AMAX
DOUBLE PRECISION A(LDA,*), SCALE(*)

SUBROUTINE DPOEQU_64(N, A, LDA, SCALE, SCOND, AMAX, INFO)

INTEGER*8 N, LDA, INFO
DOUBLE PRECISION SCOND, AMAX
DOUBLE PRECISION A(LDA,*), SCALE(*)




F95 INTERFACE
SUBROUTINE POEQU(N, A, LDA, SCALE, SCOND, AMAX, INFO)

INTEGER :: N, LDA, INFO
REAL(8) :: SCOND, AMAX
REAL(8), DIMENSION(:) :: SCALE
REAL(8), DIMENSION(:,:) :: A

SUBROUTINE POEQU_64(N, A, LDA, SCALE, SCOND, AMAX, INFO)

INTEGER(8) :: N, LDA, INFO
REAL(8) :: SCOND, AMAX
REAL(8), DIMENSION(:) :: SCALE
REAL(8), DIMENSION(:,:) :: A




C INTERFACE
#include <sunperf.h>

void  dpoequ(int  n,  double *a, int lda, double *scale, double *scond,
double *amax, int *info);

void dpoequ_64(long n, double  *a,  long  lda,  double  *scale,  double
*scond, double *amax, long *info);

Description

Oracle Solaris Studio Performance Library                           dpoequ(3P)



NAME
       dpoequ - compute row and column scalings intended to equilibrate a sym-
       metric positive definite matrix A and reduce its condition number (with
       respect to the two-norm)


SYNOPSIS
       SUBROUTINE DPOEQU(N, A, LDA, SCALE, SCOND, AMAX, INFO)

       INTEGER N, LDA, INFO
       DOUBLE PRECISION SCOND, AMAX
       DOUBLE PRECISION A(LDA,*), SCALE(*)

       SUBROUTINE DPOEQU_64(N, A, LDA, SCALE, SCOND, AMAX, INFO)

       INTEGER*8 N, LDA, INFO
       DOUBLE PRECISION SCOND, AMAX
       DOUBLE PRECISION A(LDA,*), SCALE(*)




   F95 INTERFACE
       SUBROUTINE POEQU(N, A, LDA, SCALE, SCOND, AMAX, INFO)

       INTEGER :: N, LDA, INFO
       REAL(8) :: SCOND, AMAX
       REAL(8), DIMENSION(:) :: SCALE
       REAL(8), DIMENSION(:,:) :: A

       SUBROUTINE POEQU_64(N, A, LDA, SCALE, SCOND, AMAX, INFO)

       INTEGER(8) :: N, LDA, INFO
       REAL(8) :: SCOND, AMAX
       REAL(8), DIMENSION(:) :: SCALE
       REAL(8), DIMENSION(:,:) :: A




   C INTERFACE
       #include <sunperf.h>

       void  dpoequ(int  n,  double *a, int lda, double *scale, double *scond,
                 double *amax, int *info);

       void dpoequ_64(long n, double  *a,  long  lda,  double  *scale,  double
                 *scond, double *amax, long *info);



PURPOSE
       dpoequ  computes row and column scalings intended to equilibrate a sym-
       metric positive definite 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 condi-
       tion number over all possible diagonal scalings.


ARGUMENTS
       N (input) The order of the matrix A.  N >= 0.


       A (input) The  N-by-N  symmetric positive definite matrix whose scaling
                 factors are to be computed.  Only the diagonal elements of  A
                 are referenced.


       LDA (input)
                 The leading dimension of the array A.  LDA >= max(1,N).


       SCALE (output)
                 If INFO = 0, SCALE contains the scale factors for A.


       SCOND (output)
                 If  INFO  =  0,  SCALE  contains  the  ratio  of the smallest
                 SCALE(i) to the largest SCALE(i).  If SCOND >= 0.1  and  AMAX
                 is  neither  too large nor too small, it is not worth scaling
                 by SCALE.


       AMAX (output)
                 Absolute value of largest matrix element.  If  AMAX  is  very
                 close  to  overflow  or  very  close to underflow, the matrix
                 should be scaled.


       INFO (output)
                 = 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                        dpoequ(3P)