SSISL(3)

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

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

LIBRARY
SLATEC (LINPACK)

CATEGORY
D2B1A

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

KEYWORDS
LINEAR ALGEBRA, LINPACK, MATRIX, SOLVE, SYMMETRIC

AUTHOR
Bunch, J., (UCSD)

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

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)