spbsl.f
SUBROUTINE SPBSL (ABD, LDA, N, M, B)
C***BEGIN PROLOGUE SPBSL
C***PURPOSE Solve a real symmetric positive definite band system
C using the factors computed by SPBCO or SPBFA.
C***LIBRARY SLATEC (LINPACK)
C***CATEGORY D2B2
C***TYPE SINGLE PRECISION (SPBSL-S, DPBSL-D, CPBSL-C)
C***KEYWORDS BANDED, LINEAR ALGEBRA, LINPACK, MATRIX,
C POSITIVE DEFINITE, SOLVE
C***AUTHOR Moler, C. B., (U. of New Mexico)
C***DESCRIPTION
C
C SPBSL solves the real symmetric positive definite band
C system A*X = B
C using the factors computed by SPBCO or SPBFA.
C
C On Entry
C
C ABD REAL(LDA, N)
C the output from SPBCO or SPBFA.
C
C LDA INTEGER
C the leading dimension of the array ABD .
C
C N INTEGER
C the order of the matrix A .
C
C M INTEGER
C the number of diagonals above the main diagonal.
C
C B REAL(N)
C the right hand side vector.
C
C On Return
C
C B the solution vector X .
C
C Error Condition
C
C A division by zero will occur if the input factor contains
C a zero on the diagonal. Technically, this indicates
C singularity, but it is usually caused by improper subroutine
C arguments. It will not occur if the subroutines are called
C correctly and INFO .EQ. 0 .
C
C To compute INVERSE(A) * C where C is a matrix
C with P columns
C CALL SPBCO(ABD,LDA,N,RCOND,Z,INFO)
C IF (RCOND is too small .OR. INFO .NE. 0) GO TO ...
C DO 10 J = 1, P
C CALL SPBSL(ABD,LDA,N,C(1,J))
C 10 CONTINUE
C
C***REFERENCES J. J. Dongarra, J. R. Bunch, C. B. Moler, and G. W.
C Stewart, LINPACK Users' Guide, SIAM, 1979.
C***ROUTINES CALLED SAXPY, SDOT
C***REVISION HISTORY (YYMMDD)
C 780814 DATE WRITTEN
C 890531 Changed all specific intrinsics to generic. (WRB)
C 890831 Modified array declarations. (WRB)
C 890831 REVISION DATE from Version 3.2
C 891214 Prologue converted to Version 4.0 format. (BAB)
C 900326 Removed duplicate information from DESCRIPTION section.
C (WRB)
C 920501 Reformatted the REFERENCES section. (WRB)
C***END PROLOGUE SPBSL