SNBSL(3)

SYNOPSIS
SUBROUTINE SNBSL (ABE, LDA, N, ML, MU, IPVT, B, JOB)

NAME
snbsl - Solve a real band system using the factors computed by SNBCO or SNBFA.

LIBRARY
SLATEC

CATEGORY
D2A2

TYPE
SINGLE PRECISION (SNBSL-S, DNBSL-D, CNBSL-C)

KEYWORDS
BANDED, LINEAR EQUATIONS, NONSYMMETRIC, SOLVE

AUTHOR
Voorhees, E. A., (LANL)

DESCRIPTION
SNBSL solves the real band system A * X = B or TRANS(A) * X = B using the factors computed by SNBCO or SNBFA. On Entry ABE REAL(LDA, NC) the output from SNBCO or SNBFA. NC must be .GE. 2*ML+MU+1 . LDA INTEGER the leading dimension of the array ABE . N INTEGER the order of the original matrix. ML INTEGER number of diagonals below the main diagonal. MU INTEGER number of diagonals above the main diagonal. IPVT INTEGER(N) the pivot vector from SNBCO or SNBFA. B REAL(N) the right hand side vector. JOB INTEGER = 0 to solve A*X = B . = nonzero to solve TRANS(A)*X = B , where TRANS(A) is the transpose. 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 often caused by improper arguments or improper setting of LDA. It will not occur if the subroutines are called correctly and if SNBCO has set RCOND .GT. 0.0 or SNBFA has set INFO .EQ. 0 . To compute INVERSE(A) * C where C is a matrix with P columns CALL SNBCO(ABE,LDA,N,ML,MU,IPVT,RCOND,Z) IF (RCOND is too small) GO TO ... DO 10 J = 1, P CALL SNBSL(ABE,LDA,N,ML,MU,IPVT,C(1,J),0) 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)
800717 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)
920501 Reformatted the REFERENCES section. (WRB)