SRC/spoequ.f(3)            Library Functions Manual            SRC/spoequ.f(3)

NAME
       SRC/spoequ.f

SYNOPSIS
   Functions/Subroutines
       subroutine spoequ (n, a, lda, s, scond, amax, info)
           SPOEQU

Function/Subroutine Documentation
   subroutine spoequ (integer n, real, dimension( lda, * ) a, integer lda,
       real, dimension( * ) s, real scond, real amax, integer info)
       SPOEQU

       Purpose:


           !>
           !> SPOEQU computes row and column scalings intended to equilibrate a
           !> symmetric 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 condition number over all possible diagonal
           !> scalings.
           !>

       Parameters
           N

           !>          N is INTEGER
           !>          The order of the matrix A.  N >= 0.
           !>

           A

           !>          A is REAL array, dimension (LDA,N)
           !>          The N-by-N symmetric positive definite matrix whose scaling
           !>          factors are to be computed.  Only the diagonal elements of A
           !>          are referenced.
           !>

           LDA

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

           S

           !>          S is REAL array, dimension (N)
           !>          If INFO = 0, S contains the scale factors for A.
           !>

           SCOND

           !>          SCOND is REAL
           !>          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

           !>          AMAX is REAL
           !>          Absolute value of largest matrix element.  If AMAX is very
           !>          close to overflow or very close to underflow, the matrix
           !>          should be scaled.
           !>

           INFO

           !>          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.
           !>

       Author
           Univ. of Tennessee


           Univ. of California Berkeley


           Univ. of Colorado Denver


           NAG Ltd.

       Definition at line 111 of file spoequ.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

LAPACK                          Version 3.12.0                 SRC/spoequ.f(3)