SPODI(3F)SPODI(3F)NAMESPODI - SPODI computes the determinant and inverse of a certain real
symmetric positive definite matrix (see below) using the factors computed
by SPOCO, SPOFA or SQRDC.
SYNOPSYS
SUBROUTINE SPODI(A,LDA,N,DET,JOB)
DESCRIPTION
On Entry
A REAL(LDA, N)
the output A from SPOCO or SPOFA
or the output X from SQRDC.
LDA INTEGER
the leading dimension of the array A .
N INTEGER
the order of the matrix A .
JOB INTEGER
= 11 both determinant and inverse.
= 01 inverse only.
= 10 determinant only. On Return
A If SPOCO or SPOFA was used to factor A , then
SPODI produces the upper half of INVERSE(A) .
If SQRDC was used to decompose X , then
SPODI produces the upper half of INVERSE(TRANS(X)*X),
where TRANS(X) is the transpose.
Elements of A below the diagonal are unchanged.
If the units digit of JOB is zero, A is unchanged.
DET REAL(2)
determinant of A or of TRANS(X)*X if requested.
Otherwise not referenced.
Determinant = DET(1) * 10.0**DET(2)
with 1.0 .LE. DET(1) .LT. 10.0
or DET(1) .EQ. 0.0 . Error Condition
A division by zero will occur if the input factor contains a zero on the
diagonal and the inverse is requested. It will not occur if the
subroutines are called correctly and if SPOCO or SPOFA has set INFO .EQ.
0 . LINPACK. This version dated 08/14/78 . Cleve Moler, University of
New Mexico, Argonne National Lab. Subroutines and Functions BLAS
SAXPY,SSCAL Fortran MOD
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