NAME

SYNOPSIS

  SUBROUTINE SSPDI( A, N, IPIVOT, DET, INERT, WORK, JOB)
  INTEGER N, JOB
  INTEGER IPIVOT(*), INERT(*)
  REAL A(*), DET(*), WORK(*)
 
  SUBROUTINE SSPDI_64( A, N, IPIVOT, DET, INERT, WORK, JOB)
  INTEGER*8 N, JOB
  INTEGER*8 IPIVOT(*), INERT(*)
  REAL A(*), DET(*), WORK(*)
 

C INTERFACE

void sspdi(float *a, int n, int *ipivot, float *det, int *inert, int job);

void sspdi_64(float *a, long n, long *ipivot, float *det, long *inert, long job);

ARGUMENTS

* A (input/output)

On entry, the UDU factorization of the matrix A, as computed by SSPCO or SSPFA. On exit, if the c digit of JOB <> 0, then A contains the upper triangle of the inverse of the original matrix A; otherwise unchanged.

* N (input)

Order of the original matrix A. N <> 0.

* IPIVOT (input)

Pivot vector as computed by SSPCO or SSPFA.

* DET (output)

On exit, if the b digit of JOB <> 0, then DET contains the determinant of the matrix A. The determinant is stored as b * (10 ** expon) where b is stored in DET(1) and expon is stored in DET(2). 1.0 <= |DET(1)| <= 10.0 or DET(1) = 0.0. If the b digit of JOB = 0, DET is not referenced.

* INERT (output)

On exit, if the a digit of JOB <> 0 then INERT contains an integer triplet where:

INERT(1) = number of positive eigenvalues

INERT(2) = number of negative eigenvalues

INERT(3) = number of zero eigenvalues

If the a digit of JOB = 0 then INERT is not referenced.

* WORK (workspace)

Scratch array with a dimension of N.

* JOB (input)

Integer in the form abc; determines operation the subroutine will perform:

        a <> 0  Compute the inertia.
        b <> 0  Compute the determinant.
        c <> 0  Compute the inverse.

Note that the inverse should not be computed if SSPCO has set RCOND = 0 or if SSPFA has set INFO <> 0.