d14r6.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 35 行

Private Sub Command1_Click()
    'PROGRAM D14R6
    'Driver for routine BSSTEP
    N = 4
    Dim Y(4), DYDX(4), YSCAL(4)
    X = 1#
    Y(1) = BESSJ0(X)
    Y(2) = BESSJ1(X)
    Y(3) = BESSJ(2, X)
    Y(4) = BESSJ(3, X)
    DYDX(1) = -Y(2)
    DYDX(2) = Y(1) - Y(2)
    DYDX(3) = Y(2) - 2# * Y(3)
    DYDX(4) = Y(3) - 3# * Y(4)
    For I = 1 To N
        YSCAL(I) = 1#
    Next I
    HTRY = 0.1
    Print
    Print Tab(5); "  eps        htry         hdid         hnext"
    For I = 1 To 15
        EPS = Exp(-CSng(I))
        Call BSSTEP(Y(), DYDX(), N, X, HTRY, EPS, YSCAL(), HDID, HNEXT)
        Print Tab(5); Format$(EPS, ".###0E+00");
        Print Tab(19); Format$(HTRY, ".##");
        Print Tab(29); Format$(HDID, ".###000");
        Print Tab(43); Format$(HNEXT, ".###000")
    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