SPBSL(3)

SYNOPSIS
SUBROUTINE SPBSL (ABD, LDA, N, M, B)

NAME
spbsl - Solve a real symmetric positive definite band system using the factors computed by SPBCO or SPBFA.

LIBRARY
SLATEC (LINPACK)

CATEGORY
D2B2

TYPE
SINGLE PRECISION (SPBSL-S, DPBSL-D, CPBSL-C)

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

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

DESCRIPTION
SPBSL solves the real symmetric positive definite band system A*X = B using the factors computed by SPBCO or SPBFA. On Entry ABD REAL(LDA, N) the output from SPBCO or SPBFA. LDA INTEGER the leading dimension of the array ABD . N INTEGER the order of the matrix A . M INTEGER the number of diagonals above the main diagonal. 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 SPBCO(ABD,LDA,N,RCOND,Z,INFO) IF (RCOND is too small .OR. INFO .NE. 0) GO TO ... DO 10 J = 1, P CALL SPBSL(ABD,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
890531 Changed all specific intrinsics to generic. (WRB)
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)