SGBSL(3)

SYNOPSIS
SUBROUTINE SGBSL (ABD, LDA, N, ML, MU, IPVT, B, JOB)

NAME
sgbsl - Solve the real band system A*X=B or TRANS(A)*X=B using the factors computed by SGBCO or SGBFA.

LIBRARY
SLATEC (LINPACK)

CATEGORY
D2A2

TYPE
SINGLE PRECISION (SGBSL-S, DGBSL-D, CGBSL-C)

KEYWORDS
BANDED, LINEAR ALGEBRA, LINPACK, MATRIX, SOLVE

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

DESCRIPTION
SGBSL solves the real band system A * X = B or TRANS(A) * X = B using the factors computed by SBGCO or SGBFA. On Entry ABD REAL(LDA, N) the output from SBGCO or SGBFA. LDA INTEGER the leading dimension of the array ABD . 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 SBGCO or SGBFA. 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 SBGCO has set RCOND .GT. 0.0 or SGBFA has set INFO .EQ. 0 . To compute INVERSE(A) * C where C is a matrix with P columns CALL SBGCO(ABD,LDA,N,ML,MU,IPVT,RCOND,Z) If (RCOND is too small) GO TO ... DO 10 J = 1, P CALL SGBSL(ABD,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)
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)