* F07BPF Example Program Text * Mark 21 Release. NAG Copyright 2004. * .. Parameters .. INTEGER NIN, NOUT PARAMETER (NIN=5,NOUT=6) INTEGER NMAX, KLMAX, KUMAX, NRHSMX PARAMETER (NMAX=8,KLMAX=4,KUMAX=4,NRHSMX=2) INTEGER LDAB, LDAFB, LDB, LDX PARAMETER (LDAB=KLMAX+KUMAX+1,LDAFB=LDAB+KLMAX,LDB=NMAX, + LDX=NMAX) * .. Local Scalars .. DOUBLE PRECISION RCOND INTEGER I, IFAIL, INFO, J, K, KL, KU, N, NRHS CHARACTER EQUED * .. Local Arrays .. COMPLEX *16 AB(LDAB,NMAX), AFB(LDAFB,NMAX), B(LDB,NRHSMX), + WORK(2*NMAX), X(LDX,NRHSMX) DOUBLE PRECISION BERR(NRHSMX), C(NMAX), FERR(NRHSMX), R(NMAX), + RWORK(NMAX) INTEGER IPIV(NMAX) CHARACTER CLABS(1), RLABS(1) * .. External Subroutines .. EXTERNAL X04DBF, ZGBSVX * .. Intrinsic Functions .. INTRINSIC MAX, MIN * .. Executable Statements .. WRITE (NOUT,*) 'F07BPF Example Program Results' WRITE (NOUT,*) * Skip heading in data file READ (NIN,*) READ (NIN,*) N, NRHS, KL, KU IF (N.LE.NMAX .AND. KL.LE.KLMAX .AND. KU.LE.KUMAX .AND. NRHS.LE. + NRHSMX) THEN * * Read the band matrix A and B from data file * 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) * * Solve the equations AX = B for X * CALL ZGBSVX('Equilibration','No transpose',N,KL,KU,NRHS,AB, + LDAB,AFB,LDAFB,IPIV,EQUED,R,C,B,LDB,X,LDX,RCOND, + FERR,BERR,WORK,RWORK,INFO) * IF ((INFO.EQ.0) .OR. (INFO.EQ.N+1)) THEN * * Print solution, error bounds, condition number, the form * of equilibration and the pivot growth factor * IFAIL = 0 CALL X04DBF('General',' ',N,NRHS,X,LDX,'Bracketed','F7.4', + 'Solution(s)','Integer',RLABS,'Integer',CLABS, + 80,0,IFAIL) * WRITE (NOUT,*) WRITE (NOUT,*) 'Backward errors (machine-dependent)' WRITE (NOUT,99999) (BERR(J),J=1,NRHS) WRITE (NOUT,*) WRITE (NOUT,*) + 'Estimated forward error bounds (machine-dependent)' WRITE (NOUT,99999) (FERR(J),J=1,NRHS) WRITE (NOUT,*) WRITE (NOUT,*) 'Estimate of reciprocal condition number' WRITE (NOUT,99999) RCOND WRITE (NOUT,*) IF (EQUED.EQ.'N') THEN WRITE (NOUT,*) 'A has not been equilibrated' ELSE IF (EQUED.EQ.'R') THEN WRITE (NOUT,*) 'A has been row scaled as diag(R)*A' ELSE IF (EQUED.EQ.'C') THEN WRITE (NOUT,*) 'A has been column scaled as A*diag(C)' ELSE IF (EQUED.EQ.'B') THEN WRITE (NOUT,*) + 'A has been row and column scaled as diag(R)*A*diag(C)' END IF WRITE (NOUT,*) WRITE (NOUT,*) 'Estimate of reciprocal pivot growth factor' WRITE (NOUT,99999) RWORK(1) * IF (INFO.EQ.N+1) THEN WRITE (NOUT,*) WRITE (NOUT,*) + 'The matrix A is singular to working precision' END IF ELSE WRITE (NOUT,99998) 'The (', INFO, ',', INFO, ')', + ' element of the factor U is zero' END IF ELSE WRITE (NOUT,*) + 'One or more of NMAX, KLMAX, KUMAX or NRHSMX is too small' END IF * 99999 FORMAT ((3X,1P,7E11.1)) 99998 FORMAT (1X,A,I3,A,I3,A,A) END