DPPDI(3)

SYNOPSIS
SUBROUTINE DPPDI (AP, N, DET, JOB)

NAME
dppdi - Compute the determinant and inverse of a real symmetric positive definite matrix using factors from DPPCO or DPPFA.

LIBRARY
SLATEC (LINPACK)

CATEGORY
D2B1B, D3B1B

TYPE
DOUBLE PRECISION (SPPDI-S, DPPDI-D, CPPDI-C)

KEYWORDS
DETERMINANT, INVERSE, LINEAR ALGEBRA, LINPACK, MATRIX, PACKED, POSITIVE DEFINITE

AUTHOR
Moler, C. B., (U. of New Mexico)

DESCRIPTION
DPPDI computes the determinant and inverse of a double precision symmetric positive definite matrix using the factors computed by DPPCO or DPPFA . On Entry AP DOUBLE PRECISION (N*(N+1)/2) the output from DPPCO or DPPFA. N INTEGER the order of the matrix A . JOB INTEGER = 11 both determinant and inverse. = 01 inverse only. = 10 determinant only. On Return AP the upper triangular half of the inverse . The strict lower triangle is unaltered. DET DOUBLE PRECISION(2) determinant of original matrix 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 DPOCO or DPOFA has set INFO .EQ. 0 .

REFERENCES
J. J. Dongarra, J. R. Bunch, C. B. Moler, and G. W. Stewart, LINPACK Users' Guide, SIAM, 1979.

ROUTINES CALLED
DAXPY, DSCAL

REVISION HISTORY (YYMMDD)
780814 DATE WRITTEN
890831 Modified array declarations. (WRB)
890831 REVISION DATE from Version 3.2
891214 Prologue converted to Version 4.0 format. (BAB)
900326 Removed duplicate information from DESCRIPTION section. (WRB)
920501 Reformatted the REFERENCES section. (WRB)