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man pages->IRIX man pages -> complib/SSIDI (3)
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### Contents

```
SSIDI(3F)							     SSIDI(3F)

```

### NAME[Toc][Back]

```     SSIDI   - SSIDI computes the determinant, inertia and inverse of a	real
symmetric matrix using the	factors	from SSIFA.

```

### SYNOPSYS[Toc][Back]

```      SUBROUTINE SSIDI(A,LDA,N,KPVT,DET,INERT,WORK,JOB)
```

### DESCRIPTION[Toc][Back]

```     On	Entry

A REAL(LDA,N)
the output from	SSIFA.

LDA INTEGER
the leading dimension of the array A.

N INTEGER
the order of the matrix	A.

KPVT INTEGER(N)
the pivot vector from SSIFA.

WORK REAL(N)
work vector.  Contents destroyed.

JOB INTEGER
JOB has	the decimal expansion  ABC  where
If  C .NE. 0, the inverse is computed,
If  B .NE. 0, the determinant is computed,
If  A .NE. 0, the inertia is computed.
For example, JOB = 111	gives all three.  On Return Variables not
requested by JOB are not used.

A contains	the upper triangle of the inverse of
the original matrix.  The strict lower triangle
is never referenced.

DET REAL(2)
determinant of original	matrix.
Determinant = DET(1) * 10.0**DET(2)
with 1.0 .LE. ABS(DET(1)) .LT. 10.0
or DET(1) = 0.0.

INERT INTEGER(3)
the inertia of the original matrix.
INERT(1)  =  number of positive	eigenvalues.
INERT(2)  =  number of negative	eigenvalues.
INERT(3)  =  number of zero eigenvalues.  Error	Condition

A division	by zero	may occur if the inverse is requested and  SSICO  has
set RCOND .EQ. 0.0	or  SSIFA  has set  INFO .NE. 0	.  LINPACK.  This

Page 1

SSIDI(3F)							     SSIDI(3F)

version dated 08/14/78 .  James Bunch, Univ. Calif. San Diego, Argonne
Nat. Lab Subroutines and Functions	BLAS SAXPY,SCOPY,SDOT,SSWAP Fortran
ABS,IABS,MOD

PPPPaaaaggggeeee 2222```
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