概要
本サンプルはFortran言語によりLAPACKルーチンDSPEVXを利用するサンプルプログラムです。
対称行列の半開区間![$ (-1, 1]$](img/img75.gif){kind=small}
の固有値と対応する固有ベクトルを求めます。
入力データ
（本ルーチンの詳細はDSPEVX のマニュアルページを参照）| このデータをダウンロード |
DSPEVX Example Program Data
4 :Value of N
-1.0 1.0 :Values of VL and VU
1.0 2.0 3.0 4.0
2.0 3.0 4.0
3.0 4.0
4.0 :End of matrix A
出力結果
（本ルーチンの詳細はDSPEVX のマニュアルページを参照）| この出力例をダウンロード |
DSPEVX Example Program Results
Number of eigenvalues found = 2
Eigenvalues
-0.5146 -0.2943
Selected eigenvectors
1 2
1 -0.5144 -0.2767
2 0.4851 0.6634
3 0.5420 -0.6504
4 -0.4543 0.2457
ソースコード
（本ルーチンの詳細はDSPEVX のマニュアルページを参照）※本サンプルソースコードのご利用手順は「サンプルのコンパイル及び実行方法」をご参照下さい。
| このソースコードをダウンロード |
Program dspevx_example
! DSPEVX Example Program Text
! Copyright 2017, Numerical Algorithms Group Ltd. http://www.nag.com
! .. Use Statements ..
Use lapack_example_aux, Only: nagf_blas_damax_val, &
nagf_file_print_matrix_real_gen
Use lapack_interfaces, Only: dspevx
Use lapack_precision, Only: dp
! .. Implicit None Statement ..
Implicit None
! .. Parameters ..
Real (Kind=dp), Parameter :: zero = 0.0E+0_dp
Integer, Parameter :: nin = 5, nout = 6
Character (1), Parameter :: uplo = 'U'
! .. Local Scalars ..
Real (Kind=dp) :: abstol, r, vl, vu
Integer :: i, ifail, il, info, iu, j, k, ldz, m, n
! .. Local Arrays ..
Real (Kind=dp), Allocatable :: ap(:), w(:), work(:), z(:, :)
Integer, Allocatable :: iwork(:), jfail(:)
! .. Executable Statements ..
Write (nout, *) 'DSPEVX Example Program Results'
Write (nout, *)
! Skip heading in data file
Read (nin, *)
Read (nin, *) n
ldz = n
m = n
Allocate (ap((n*(n+1))/2), w(n), work(8*n), z(ldz,m), iwork(5*n), jfail( &
n))
! Read the lower and upper bounds of the interval to be searched,
! and read the upper or lower triangular part of the matrix A
! from data file
Read (nin, *) vl, vu
If (uplo=='U') Then
Read (nin, *)((ap(i+(j*(j-1))/2),j=i,n), i=1, n)
Else If (uplo=='L') Then
Read (nin, *)((ap(i+((2*n-j)*(j-1))/2),j=1,i), i=1, n)
End If
! Set the absolute error tolerance for eigenvalues. With ABSTOL
! set to zero, the default value is used instead
abstol = zero
! Solve the symmetric eigenvalue problem
Call dspevx('Vectors', 'Values in range', uplo, n, ap, vl, vu, il, iu, &
abstol, m, w, z, ldz, work, iwork, jfail, info)
If (info>=0) Then
! Print solution
Write (nout, 100) 'Number of eigenvalues found =', m
Write (nout, *)
Write (nout, *) 'Eigenvalues'
Write (nout, 110) w(1:m)
Flush (nout)
! Normalize the eigenvectors: largest element positive
Do i = 1, m
Call nagf_blas_damax_val(n, z(1,i), 1, k, r)
If (z(k,i)<zero) Then
z(1:n, i) = -z(1:n, i)
End If
End Do
! ifail: behaviour on error exit
! =0 for hard exit, =1 for quiet-soft, =-1 for noisy-soft
ifail = 0
Call nagf_file_print_matrix_real_gen('General', ' ', n, m, z, ldz, &
'Selected eigenvectors', ifail)
If (info>0) Then
Write (nout, 100) 'INFO eigenvectors failed to converge, INFO =', &
info
Write (nout, *) 'Indices of eigenvectors that did not converge'
Write (nout, 120) jfail(1:m)
End If
Else
Write (nout, 100) 'Failure in DSPEVX. INFO =', info
End If
100 Format (1X, A, I5)
110 Format (3X, (8F8.4))
120 Format (3X, (8I8))
End Program