概要
本サンプルはFortran言語によりLAPACKルーチンDSYEVRを利用するサンプルプログラムです。
対称行列の指標が の範囲に含まれる固有値と対応する固有ベクトルを求めます。必要で利用されたワークスペースの情報も合わせて出力されます。
入力データ
(本ルーチンの詳細はDSYEVR のマニュアルページを参照)1 2 3 4 5 6 7 8
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DSYEVR Example Program Data 4 2 3 :Values of N, IL and IU 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DSYEVR のマニュアルページを参照)1 2 3 4 5 6 7 8 9 10 11 12
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DSYEVR Example Program Results Selected eigenvalues -0.5146 -0.2943 Warning: Floating invalid operation occurred Warning: Floating divide by zero occurred 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DSYEVR 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。
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Program dsyevr_example ! DSYEVR Example Program Text ! Copyright 2017, Numerical Algorithms Group Ltd. http://www.nag.com ! .. Use Statements .. Use lapack_example_aux, Only: nagf_file_print_matrix_real_gen Use lapack_interfaces, Only: dsyevr Use lapack_precision, Only: dp ! .. Implicit None Statement .. Implicit None ! .. Parameters .. Real (Kind=dp), Parameter :: zero = 0.0E+0_dp Integer, Parameter :: nb = 64, nin = 5, nout = 6 ! .. Local Scalars .. Real (Kind=dp) :: abstol, vl, vu Integer :: i, ifail, il, info, iu, lda, ldz, liwork, lwork, m, n ! .. Local Arrays .. Real (Kind=dp), Allocatable :: a(:, :), w(:), work(:), z(:, :) Real (Kind=dp) :: dummy(1) Integer :: idum(1) Integer, Allocatable :: isuppz(:), iwork(:) ! .. Intrinsic Procedures .. Intrinsic :: max, nint ! .. Executable Statements .. Write (nout, *) 'DSYEVR Example Program Results' Write (nout, *) ! Skip heading in data file and read N and the lower and upper ! indices of the smallest and largest eigenvalues to be found Read (nin, *) Read (nin, *) n, il, iu lda = n ldz = n m = n Allocate (a(lda,n), w(n), z(ldz,m), isuppz(2*m)) ! Use routine workspace query to get optimal workspace. lwork = -1 liwork = -1 Call dsyevr('Vectors', 'I', 'Upper', n, a, lda, vl, vu, il, iu, abstol, & m, w, z, ldz, isuppz, dummy, lwork, idum, liwork, info) ! Make sure that there is enough workspace for block size nb. lwork = max((nb+6)*n, nint(dummy(1))) liwork = max(10*n, idum(1)) Allocate (work(lwork), iwork(liwork)) ! Read the upper triangular part of the matrix A from data file Read (nin, *)(a(i,i:n), i=1, n) ! 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 dsyevr('Vectors', 'I', 'Upper', n, a, lda, vl, vu, il, iu, abstol, & m, w, z, ldz, isuppz, work, lwork, iwork, liwork, info) If (info==0) Then ! Print solution Write (nout, *) 'Selected eigenvalues' Write (nout, 100) w(1:m) Flush (nout) ! 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) Else Write (nout, 110) 'Failure in DSYEVR. INFO =', info End If 100 Format (3X, (8F8.4)) 110 Format (1X, A, I5) End Program