python中的黄金分割法，python黄金分割法,''' a,b = br

python中的黄金分割法，python黄金分割法,''' a,b = br

''' a,b = bracket(f,xStart,h)    Finds the brackets (a,b) of a minimum point of the    user-supplied scalar function f(x).    The search starts downhill from xStart with a step    length h.    x,fMin = search(f,a,b,tol=1.0e-6)    Golden section method for determining x that minimizes    the user-supplied scalar function f(x).    The minimum must be bracketed in (a,b).'''       from math import log, ceildef bracket(f,x1,h):    c = 1.618033989     f1 = f(x1)    x2 = x1 + h; f2 = f(x2)  # Determine downhill direction and change sign of h if needed    if f2 > f1:        h = -h        x2 = x1 + h; f2 = f(x2)      # Check if minimum between x1 - h and x1 + h        if f2 > f1: return x2,x1 - h   # Search loop    for i in range (100):            h = c*h        x3 = x2 + h; f3 = f(x3)        if f3 > f2: return x1,x3        x1 = x2; x2 = x3        f1 = f2; f2 = f3    print "Bracket did not find a mimimum"        def search(f,a,b,tol=1.0e-9):    nIter = int(ceil(-2.078087*log(tol/abs(b-a)))) # Eq. (10.4)    R = 0.618033989    C = 1.0 - R  # First telescoping    x1 = R*a + C*b; x2 = C*a + R*b    f1 = f(x1); f2 = f(x2)  # Main loop    for i in range(nIter):        if f1 > f2:            a = x1            x1 = x2; f1 = f2            x2 = C*a + R*b; f2 = f(x2)        else:            b = x2            x2 = x1; f2 = f1            x1 = R*a + C*b; f1 = f(x1)    if f1 < f2: return x1,f1    else: return x2,f2