* F07BHF Example Program Text * Mark 15 Release. NAG Copyright 1991. * .. Parameters .. INTEGER NIN, NOUT PARAMETER (NIN=5,NOUT=6) DOUBLE PRECISION ZERO PARAMETER (ZERO=0.0D0) INTEGER NMAX, NRHMAX, KLMAX, KUMAX, LDAB, LDAFB, LDB, LDX PARAMETER (NMAX=8,NRHMAX=NMAX,KLMAX=8,KUMAX=8, + LDAB=KLMAX+KUMAX+1,LDAFB=2*KLMAX+KUMAX+1, + LDB=NMAX,LDX=NMAX) CHARACTER TRANS PARAMETER (TRANS='N') * .. Local Scalars .. INTEGER I, IFAIL, INFO, J, K, KL, KU, N, NRHS * .. Local Arrays .. DOUBLE PRECISION AB(LDAB,NMAX), AFB(LDAFB,NMAX), B(LDB,NRHMAX), + BERR(NRHMAX), FERR(NRHMAX), WORK(3*NMAX), + X(LDX,NMAX) INTEGER IPIV(NMAX), IWORK(NMAX) * .. External Subroutines .. EXTERNAL DGBRFS, DGBTRF, DGBTRS, F06QFF, F06QHF, X04CAF * .. Intrinsic Functions .. INTRINSIC MAX, MIN * .. Executable Statements .. WRITE (NOUT,*) 'F07BHF Example Program Results' * Skip heading in data file READ (NIN,*) READ (NIN,*) N, NRHS, KL, KU IF (N.LE.NMAX .AND. NRHS.LE.NRHMAX .AND. KL.LE.KLMAX .AND. KU.LE. + KUMAX) THEN * * Set A to zero to avoid referencing uninitialized elements * CALL F06QHF('General',KL+KU+1,N,ZERO,ZERO,AB,LDAB) * * Read A and B from data file, and copy A to AFB and B to X * K = KU + 1 READ (NIN,*) ((AB(K+I-J,J),J=MAX(I-KL,1),MIN(I+KU,N)),I=1,N) READ (NIN,*) ((B(I,J),J=1,NRHS),I=1,N) * CALL F06QFF('General',KL+KU+1,N,AB,LDAB,AFB(KL+1,1),LDAFB) * CALL F06QFF('General',N,NRHS,B,LDB,X,LDX) * * Factorize A in the array AFB * CALL DGBTRF(N,N,KL,KU,AFB,LDAFB,IPIV,INFO) * WRITE (NOUT,*) IF (INFO.EQ.0) THEN * * Compute solution in the array X * CALL DGBTRS(TRANS,N,KL,KU,NRHS,AFB,LDAFB,IPIV,X,LDX,INFO) * * Improve solution, and compute backward errors and * estimated bounds on the forward errors * CALL DGBRFS(TRANS,N,KL,KU,NRHS,AB,LDAB,AFB,LDAFB,IPIV,B,LDB, + X,LDX,FERR,BERR,WORK,IWORK,INFO) * * Print solution * IFAIL = 0 * CALL X04CAF('General',' ',N,NRHS,X,LDX,'Solution(s)',IFAIL) * WRITE (NOUT,*) WRITE (NOUT,*) 'Backward errors (machine-dependent)' WRITE (NOUT,99999) (BERR(J),J=1,NRHS) WRITE (NOUT,*) + 'Estimated forward error bounds (machine-dependent)' WRITE (NOUT,99999) (FERR(J),J=1,NRHS) ELSE WRITE (NOUT,*) 'The factor U is singular' END IF END IF STOP * 99999 FORMAT ((3X,1P,7E11.1)) END