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slaqsp.f(3) LAPACK slaqsp.f(3)

NAME

slaqsp.f -

SYNOPSIS

Functions/Subroutines


subroutine slaqsp (UPLO, N, AP, S, SCOND, AMAX, EQUED)
 
SLAQSP

Function/Subroutine Documentation

subroutine slaqsp (characterUPLO, integerN, real, dimension( * )AP, real, dimension( * )S, realSCOND, realAMAX, characterEQUED)

SLAQSP
Purpose:
 
 SLAQSP equilibrates a symmetric matrix A using the scaling factors
 in the vector S.
 
Parameters:
UPLO
          UPLO is CHARACTER*1
          Specifies whether the upper or lower triangular part of the
          symmetric matrix A is stored.
          = 'U':  Upper triangular
          = 'L':  Lower triangular
 
N
          N is INTEGER
          The order of the matrix A.  N >= 0.
 
AP
          AP is REAL array, dimension (N*(N+1)/2)
          On entry, the upper or lower triangle of the symmetric matrix
          A, packed columnwise in a linear array.  The j-th column of A
          is stored in the array AP as follows:
          if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j;
          if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = A(i,j) for j<=i<=n.
On exit, the equilibrated matrix: diag(S) * A * diag(S), in the same storage format as A.
 
S
          S is REAL array, dimension (N)
          The scale factors for A.
 
SCOND
          SCOND is REAL
          Ratio of the smallest S(i) to the largest S(i).
 
AMAX
          AMAX is REAL
          Absolute value of largest matrix entry.
 
EQUED
          EQUED is CHARACTER*1
          Specifies whether or not equilibration was done.
          = 'N':  No equilibration.
          = 'Y':  Equilibration was done, i.e., A has been replaced by
                  diag(S) * A * diag(S).
 
Internal Parameters:
 
  THRESH is a threshold value used to decide if scaling should be done
  based on the ratio of the scaling factors.  If SCOND < THRESH,
  scaling is done.
LARGE and SMALL are threshold values used to decide if scaling should be done based on the absolute size of the largest matrix element. If AMAX > LARGE or AMAX < SMALL, scaling is done.
 
Author:
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
November 2011
 
Definition at line 126 of file slaqsp.f.

Author

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