DSISL(3)

SYNOPSIS
SUBROUTINE DSISL (A, LDA, N, KPVT, B)

NAME
dsisl - Solve a real symmetric system using the factors obtained from SSIFA.

LIBRARY
SLATEC (LINPACK)

CATEGORY
D2B1A

TYPE
DOUBLE PRECISION (SSISL-S, DSISL-D, CHISL-C, CSISL-C)

KEYWORDS
LINEAR ALGEBRA, LINPACK, MATRIX, SOLVE, SYMMETRIC

AUTHOR
Bunch, J., (UCSD)

DESCRIPTION
DSISL solves the double precision symmetric system A * X = B using the factors computed by DSIFA. On Entry A DOUBLE PRECISION(LDA,N) the output from DSIFA. LDA INTEGER the leading dimension of the array A . N INTEGER the order of the matrix A . KPVT INTEGER(N) the pivot vector from DSIFA. B DOUBLE PRECISION(N) the right hand side vector. On Return B the solution vector X . Error Condition A division by zero may occur if DSICO has set RCOND .EQ. 0.0 or DSIFA has set INFO .NE. 0 . To compute INVERSE(A) * C where C is a matrix with P columns CALL DSIFA(A,LDA,N,KPVT,INFO) IF (INFO .NE. 0) GO TO ... DO 10 J = 1, P CALL DSISL(A,LDA,N,KPVT,C(1,J)) 10 CONTINUE

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

ROUTINES CALLED
DAXPY, DDOT

REVISION HISTORY (YYMMDD)
780814 DATE WRITTEN
890531 Changed all specific intrinsics to generic. (WRB)
890831 Modified array declarations. (WRB)
891107 Modified routine equivalence list. (WRB)
891107 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)