ssidi.f
SUBROUTINE SSIDI (A, LDA, N, KPVT, DET, INERT, WORK, JOB)
C***BEGIN PROLOGUE SSIDI
C***PURPOSE Compute the determinant, inertia and inverse of a real
C symmetric matrix using the factors from SSIFA.
C***LIBRARY SLATEC (LINPACK)
C***CATEGORY D2B1A, D3B1A
C***TYPE SINGLE PRECISION (SSIDI-S, DSIDI-D, CHIDI-C, CSIDI-C)
C***KEYWORDS DETERMINANT, INVERSE, LINEAR ALGEBRA, LINPACK, MATRIX,
C SYMMETRIC
C***AUTHOR Bunch, J., (UCSD)
C***DESCRIPTION
C
C SSIDI computes the determinant, inertia and inverse
C of a real symmetric matrix using the factors from SSIFA.
C
C On Entry
C
C A REAL(LDA,N)
C the output from SSIFA.
C
C LDA INTEGER
C the leading dimension of the array A.
C
C N INTEGER
C the order of the matrix A.
C
C KPVT INTEGER(N)
C the pivot vector from SSIFA.
C
C WORK REAL(N)
C work vector. Contents destroyed.
C
C JOB INTEGER
C JOB has the decimal expansion ABC where
C If C .NE. 0, the inverse is computed,
C If B .NE. 0, the determinant is computed,
C If A .NE. 0, the inertia is computed.
C
C For example, JOB = 111 gives all three.
C
C On Return
C
C Variables not requested by JOB are not used.
C
C A contains the upper triangle of the inverse of
C the original matrix. The strict lower triangle
C is never referenced.
C
C DET REAL(2)
C determinant of original matrix.
C Determinant = DET(1) * 10.0**DET(2)
C with 1.0 .LE. ABS(DET(1)) .LT. 10.0
C or DET(1) = 0.0.
C
C INERT INTEGER(3)
C the inertia of the original matrix.
C INERT(1) = number of positive eigenvalues.
C INERT(2) = number of negative eigenvalues.
C INERT(3) = number of zero eigenvalues.
C
C Error Condition
C
C A division by zero may occur if the inverse is requested
C and SSICO has set RCOND .EQ. 0.0
C or SSIFA has set INFO .NE. 0 .
C
C***REFERENCES J. J. Dongarra, J. R. Bunch, C. B. Moler, and G. W.
C Stewart, LINPACK Users' Guide, SIAM, 1979.
C***ROUTINES CALLED SAXPY, SCOPY, SDOT, SSWAP
C***REVISION HISTORY (YYMMDD)
C 780814 DATE WRITTEN
C 890531 Changed all specific intrinsics to generic. (WRB)
C 890831 Modified array declarations. (WRB)
C 891107 Modified routine equivalence list. (WRB)
C 891107 REVISION DATE from Version 3.2
C 891214 Prologue converted to Version 4.0 format. (BAB)
C 900326 Removed duplicate information from DESCRIPTION section.
C (WRB)
C 920501 Reformatted the REFERENCES section. (WRB)
C***END PROLOGUE SSIDI