Program f07bffe ! F07BFF Example Program Text ! Mark 24 Release. NAG Copyright 2012. ! .. Use Statements .. Use nag_library, Only: dgbequ, dscal, f06fcf, nag_wp, x02ajf, x02amf, & x02bhf, x04cef ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Real (Kind=nag_wp), Parameter :: one = 1.0_nag_wp Real (Kind=nag_wp), Parameter :: thresh = 0.1_nag_wp Integer, Parameter :: nin = 5, nout = 6 ! .. Local Scalars .. Real (Kind=nag_wp) :: amax, big, colcnd, rowcnd, small Integer :: i, i0, i1, ifail, ilen, info, j, k, & kl, ku, ldab, n ! .. Local Arrays .. Real (Kind=nag_wp), Allocatable :: ab(:,:), c(:), r(:) ! .. Intrinsic Procedures .. Intrinsic :: max, min, real ! .. Executable Statements .. Write (nout,*) 'F07BFF Example Program Results' Write (nout,*) Flush (nout) ! Skip heading in data file Read (nin,*) Read (nin,*) n, kl, ku ldab = kl + ku + 1 Allocate (ab(ldab,n),c(n),r(n)) ! Read the band matrix A 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) ! Print the matrix A ! ifail: behaviour on error exit ! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft ifail = 0 Call x04cef(n,n,kl,ku,ab,ldab,'Matrix A',ifail) Write (nout,*) ! Compute row and column scaling factors ! The NAG name equivalent of dgbequ is f07bff Call dgbequ(n,n,kl,ku,ab,ldab,r,c,rowcnd,colcnd,amax,info) If (info>0) Then If (info<=n) Then Write (nout,99999) 'Row ', info, ' of A is exactly zero' Else Write (nout,99999) 'Column ', info - n, ' of A is exactly zero' End If Else ! Print ROWCND, COLCND, AMAX and the scale factors Write (nout,99998) 'ROWCND =', rowcnd, ', COLCND =', colcnd, & ', AMAX =', amax Write (nout,*) Write (nout,*) 'Row scale factors' Write (nout,99997) r(1:n) Write (nout,*) Write (nout,*) 'Column scale factors' Write (nout,99997) c(1:n) Write (nout,*) Flush (nout) ! Compute values close to underflow and overflow small = x02amf()/(x02ajf()*real(x02bhf(),kind=nag_wp)) big = one/small If ((rowcnd>=thresh) .And. (amax>=small) .And. (amax<=big)) Then If (colcnd=thresh) Then ! Just row scale A Do j = 1, n i0 = max(1,j-ku) i1 = 1 + i0 - (j-ku) ilen = min(n,j+kl) - i0 + 1 Call f06fcf(ilen,r(i0),1,ab(i1,j),1) End Do Else ! Row and column scale A Do j = 1, n i0 = max(1,j-ku) i1 = 1 + i0 - (j-ku) ilen = min(n,j+kl) - i0 + 1 Call dscal(ilen,c(j),ab(i1,j),1) Call f06fcf(ilen,r(i0),1,ab(i1,j),1) End Do End If ! Print the scaled matrix ifail = 0 Call x04cef(n,n,kl,ku,ab,ldab,'Scaled matrix',ifail) End If 99999 Format (1X,A,I4,A) 99998 Format (1X,3(A,1P,E8.1)) 99997 Format ((1X,1P,7E11.1)) End Program f07bffe