DPPSL(3)

SYNOPSIS
SUBROUTINE DPPSL (AP, N, B)

NAME
dppsl - Solve the real symmetric positive definite system using the factors computed by DPPCO or DPPFA.

LIBRARY
SLATEC (LINPACK)

CATEGORY
D2B1B

TYPE
DOUBLE 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
DPPSL solves the double precision symmetric positive definite system A * X = B 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 . B DOUBLE PRECISION(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 DPPCO(AP,N,RCOND,Z,INFO) IF (RCOND is too small .OR. INFO .NE. 0) GO TO ... DO 10 J = 1, P CALL DPPSL(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
DAXPY, DDOT

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)