DGBSL(3F)DGBSL(3F)NAMEDGBSL - DGBSL solves the double precision band system A * X = B or
TRANS(A) * X = B using the factors computed by DGBCO or DGBFA.
SYNOPSYS
SUBROUTINE DGBSL(ABD,LDA,N,ML,MU,IPVT,B,JOB)
DESCRIPTION
On Entry
ABD DOUBLE PRECISION(LDA, N)
the output from DGBCO or DGBFA.
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 DGBCO or DGBFA.
B DOUBLE PRECISION(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 DGBCO has set RCOND .GT. 0.0
or DGBFA has set INFO .EQ. 0 . To compute INVERSE(A) * C where C is
a matrix with P columns
CALL DGBCO(ABD,LDA,N,ML,MU,IPVT,RCOND,Z)
IF (RCOND is too small) GO TO ...
DO 10 J = 1, P
CALL DGBSL(ABD,LDA,N,ML,MU,IPVT,C(1,J),0) 10 CONTINUE LINPACK. This
version dated 08/14/78 . Cleve Moler, University of New Mexico, Argonne
National Lab. Subroutines and Functions BLAS DAXPY,DDOT Fortran MIN0
Page 1