d14r4.txt

来自「VB常用数值算法集 内含有解线性代数方程组」· 文本 代码 · 共 36 行

Dim KMAX, KOUNT, DXSAV
Private Sub Command1_Click()
    'PROGRAM D14R4
    'Driver for routine ODEINT
    NVAR = 4
    Dim VSTART(4), XP(200), YP(10, 200)
    X1 = 1#
    X2 = 10#
    VSTART(1) = BESSJ0(X1)
    VSTART(2) = BESSJ1(X1)
    VSTART(3) = BESSJ(2, X1)
    VSTART(4) = BESSJ(3, X1)
    EPS = 0.0001
    H1 = 0.1
    HMIN = 0#
    KMAX = 100
    DXSAV = (X2 - X1) / 20#
    Call ODEINT(VSTART, NVAR, X1, X2, EPS, H1, HMIN, NOK, NBAD, XP(), YP())
    Print
    Print Tab(5); "Successful step: "; NOK
    Print Tab(5); "Bad step: "; NBAD
    Print Tab(5); "Stored intermediate values:  "; KOUNT
    Print
    Print Tab(5); "   X          Integral      BESSJ(3,X)"
    For I = 1 To KOUNT
        Print Tab(5); Format$(XP(I), "##.###0");
        Print Tab(19); Format$(YP(4, I), "##.#####0");
        Print Tab(33); Format$(BESSJ(3, XP(I)), "##.#####0");
    Next I
End Sub
Sub DERIVS(X, Y(), DYDX())
    DYDX(1) = -Y(2)
    DYDX(2) = Y(1) - (1# / X) * Y(2)
    DYDX(3) = Y(2) - (2# / X) * Y(3)
    DYDX(4) = Y(3) - (3# / X) * Y(4)
End Sub