SPPSL(3)

SYNOPSIS
SUBROUTINE SPPSL (AP, N, B)

NAME
sppsl - Solve the real symmetric positive definite system using the factors computed by SPPCO or SPPFA.

LIBRARY
SLATEC (LINPACK)

CATEGORY
D2B1B

TYPE
SINGLE PRECISION (SPPSL-S, DPPSL-D, CPPSL-C)

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

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

DESCRIPTION
SPPSL solves the real symmetric positive definite system A * X = B using the factors computed by SPPCO or SPPFA. On Entry AP REAL (N*(N+1)/2) the output from SPPCO or SPPFA. 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 SPPCO(AP,N,RCOND,Z,INFO) IF (RCOND is too small .OR. INFO .NE. 0) GO TO ... DO 10 J = 1, P CALL SPPSL(AP,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)