SSPDI(3F)SSPDI(3F)NAMESSPDI - SSPDI computes the determinant, inertia and inverse of a real
symmetric matrix using the factors from SSPFA, where the matrix is stored
in packed form.
SYNOPSYS
SUBROUTINE SSPDI(AP,N,KPVT,DET,INERT,WORK,JOB)
DESCRIPTION
On Entry
AP REAL (N*(N+1)/2)
the output from SSPFA.
N INTEGER
the order of the matrix A.
KPVT INTEGER(N)
the pivot vector from SSPFA.
WORK REAL(N)
work vector. Contents ignored.
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.
AP contains the upper triangle of the inverse of
the original matrix, stored in packed form.
The columns of the upper triangle are stored
sequentially in a one-dimensional array.
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 will occur if the inverse is requested and SSPCO has
set RCOND .EQ. 0.0 or SSPFA has set INFO .NE. 0 . LINPACK. This
version dated 08/14/78 . James Bunch, Univ. Calif. San Diego, Argonne
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SSPDI(3F)SSPDI(3F)
Nat. Lab. Subroutines and Functions BLAS SAXPY,SCOPY,SDOT,SSWAP Fortran
ABS,IABS,MOD
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