SPOSL(3)

SYNOPSIS
SUBROUTINE SPOSL (A, LDA, N, B)

NAME
sposl - Solve the real symmetric positive definite linear system using the factors computed by SPOCO or SPOFA.

LIBRARY
SLATEC (LINPACK)

CATEGORY
D2B1B

TYPE
SINGLE PRECISION (SPOSL-S, DPOSL-D, CPOSL-C)

KEYWORDS
LINEAR ALGEBRA, LINPACK, MATRIX, POSITIVE DEFINITE, SOLVE

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

DESCRIPTION
SPOSL solves the real symmetric positive definite system A * X = B using the factors computed by SPOCO or SPOFA. On Entry A REAL(LDA, N) the output from SPOCO or SPOFA. LDA INTEGER the leading dimension of the array A . N INTEGER the order of the matrix A . B REAL(N) the right hand side vector. On Return B the solution vector X . Error Condition A division by zero will occur if the input factor contains a zero on the diagonal. Technically, this indicates singularity, but it is usually caused by improper subroutine arguments. It will not occur if the subroutines are called correctly and INFO .EQ. 0 . To compute INVERSE(A) * C where C is a matrix with P columns CALL SPOCO(A,LDA,N,RCOND,Z,INFO) IF (RCOND is too small .OR. INFO .NE. 0) GO TO ... DO 10 J = 1, P CALL SPOSL(A,LDA,N,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
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)