* F07GBF Example Program Text * Mark 21 Release. NAG Copyright 2004. * .. Parameters .. INTEGER NIN, NOUT PARAMETER (NIN=5,NOUT=6) INTEGER NMAX PARAMETER (NMAX=8) INTEGER LDB, LDX, NRHSMX PARAMETER (LDB=NMAX,LDX=NMAX,NRHSMX=NMAX) CHARACTER UPLO PARAMETER (UPLO='U') * .. Local Scalars .. DOUBLE PRECISION RCOND INTEGER I, IFAIL, INFO, J, N, NRHS CHARACTER EQUED * .. Local Arrays .. DOUBLE PRECISION AFP((NMAX*(NMAX+1))/2), AP((NMAX*(NMAX+1))/2), + B(LDB,NRHSMX), BERR(NRHSMX), FERR(NRHSMX), + S(NMAX), WORK(3*NMAX), X(LDX,NRHSMX) INTEGER IWORK(NMAX) * .. External Subroutines .. EXTERNAL DPPSVX, X04CAF * .. Executable Statements .. WRITE (NOUT,*) 'F07GBF Example Program Results' WRITE (NOUT,*) * Skip heading in data file READ (NIN,*) READ (NIN,*) N, NRHS IF (N.LE.NMAX .AND. NRHS.LE.NRHSMX) THEN * * Read the upper or lower triangular part of the matrix A from * data file * IF (UPLO.EQ.'U') THEN READ (NIN,*) ((AP(I+(J*(J-1))/2),J=I,N),I=1,N) ELSE IF (UPLO.EQ.'L') THEN READ (NIN,*) ((AP(I+((2*N-J)*(J-1))/2),J=1,I),I=1,N) END IF * * Read B from data file * READ (NIN,*) ((B(I,J),J=1,NRHS),I=1,N) * * Solve the equations AX = B for X * CALL DPPSVX('Equilibration',UPLO,N,NRHS,AP,AFP,EQUED,S,B,LDB,X, + LDX,RCOND,FERR,BERR,WORK,IWORK,INFO) * IF ((INFO.EQ.0) .OR. (INFO.EQ.N+1)) THEN * * Print solution, error bounds, condition number and the form * of equilibration * 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,*) 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.'Y') THEN WRITE (NOUT,*) + 'A has been row and column scaled as diag(S)*A*diag(S)' END IF * 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 leading minor of order ', INFO, + ' is not positive definite' END IF ELSE WRITE (NOUT,*) 'NMAX and/or NRHSMX too small' END IF * 99999 FORMAT ((3X,1P,7E11.1)) 99998 FORMAT (1X,A,I3,A) END