Program f07hffe ! F07HFF Example Program Text ! Mark 24 Release. NAG Copyright 2012. ! .. Use Statements .. Use nag_library, Only: dpbequ, 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 Character (1), Parameter :: uplo = 'U' ! .. Local Scalars .. Real (Kind=nag_wp) :: amax, big, scond, small Integer :: i, i0, i1, ifail, ilen, info, j, kd, & ldab, n ! .. Local Arrays .. Real (Kind=nag_wp), Allocatable :: ab(:,:), s(:) ! .. Intrinsic Procedures .. Intrinsic :: max, min, real ! .. Executable Statements .. Write (nout,*) 'F07HFF Example Program Results' Write (nout,*) Flush (nout) ! Skip heading in data file Read (nin,*) Read (nin,*) n, kd ldab = kd + 1 Allocate (ab(ldab,n),s(n)) ! Read the upper or lower triangular part of the band matrix A ! from data file If (uplo=='U') Then Do i = 1, n Read (nin,*)(ab(kd+1+i-j,j),j=i,min(n,i+kd)) End Do Else If (uplo=='L') Then Do i = 1, n Read (nin,*)(ab(1+i-j,j),j=max(1,i-kd),i) End Do End If ! Print the matrix A ! ifail: behaviour on error exit ! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft ifail = 0 If (uplo=='U') Then Call x04cef(n,n,0,kd,ab,ldab,'Matrix A',ifail) Else If (uplo=='L') Then Call x04cef(n,n,kd,0,ab,ldab,'Matrix A',ifail) End If Write (nout,*) ! Compute diagonal scaling factors ! The NAG name equivalent of dpbequ is f07hff Call dpbequ(uplo,n,kd,ab,ldab,s,scond,amax,info) If (info>0) Then Write (nout,99999) 'Diagonal element', info, ' of A is non positive' Else ! Print SCOND, AMAX and the scale factors Write (nout,99998) 'SCOND =', scond, ', AMAX =', amax Write (nout,*) Write (nout,*) 'Diagonal scaling factors' Write (nout,99997) s(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 ((scondbig)) Then ! Scale A If (uplo=='U') Then ! The NAG name equivalent of dscal is f06edf Do j = 1, n i0 = max(1,j-kd) i1 = 1 + i0 - (j-kd) ilen = j - i0 + 1 Call dscal(ilen,s(j),ab(i1,j),1) Call f06fcf(ilen,s(i0),1,ab(i1,j),1) End Do Else If (uplo=='L') Then Do j = 1, n i1 = 1 ilen = min(n,j+kd) - j + 1 Call dscal(ilen,s(j),ab(i1,j),1) Call f06fcf(ilen,s(j),1,ab(i1,j),1) End Do End If ! Print the scaled matrix ifail = 0 If (uplo=='U') Then Call x04cef(n,n,0,kd,ab,ldab,'Scaled matrix',ifail) Else If (uplo=='L') Then Call x04cef(n,n,kd,0,ab,ldab,'Scaled matrix',ifail) End If End If End If 99999 Format (1X,A,I4,A) 99998 Format (1X,2(A,1P,E8.1)) 99997 Format ((1X,1P,7E11.1)) End Program f07hffe