关于cs231作业1双层神经网络梯度检查的澄清

Question

cs231赋值1Q4: Two-Layer Neural Network (25 points)中的梯度检查逻辑似乎有错误

它正在做梯度检查

two_layer_net.ipynb使用参数W定义lambda，但未使用

from cs231n.gradient_check import eval_numerical_gradient
loss, grads = net.loss(X, y, reg=0.05)
for param_name in grads:
    f = lambda W: net.loss(X, y, reg=0.05)[0]   # <--- W is not used anywhere
    # f = lambda : net.loss(X, y, reg=0.05)[0]  # <--- Should be like this
    param_grad_num = \
        eval_numerical_gradient(f,              # <--- lambda passed as f
                                net.params[param_name], verbose=False)

cs231n.gradient\u check.eval\u numerical\u gradient.py作为f(x)调用，但x将不使用

def eval_numerical_gradient(f, x, verbose=True, h=0.00001):
    """
    a naive implementation of numerical gradient of f at x
    - f should be a function that takes a single argument  # <--- Should have no need to take an argument
    - x is the point (numpy array) to evaluate the gradient at
    """
    grad = np.zeros_like(x)
    it = np.nditer(x, flags=['multi_index'], op_flags=['readwrite'])
    while not it.finished:

        # evaluate function at x+h
        ix = it.multi_index
        oldval = x[ix]
        x[ix] = oldval + h # increment by h
        fxph = f(x) # evalute f(x + h)          # <--- x will not be used 
        # fxph = f()                            # <--- Should be like this
        x[ix] = oldval - h
        fxmh = f(x) # evaluate f(x - h)
        x[ix] = oldval # restore

        # compute the partial derivative with centered formula
        grad[ix] = (fxph - fxmh) / (2 * h) # the slope
        it.iternext() # step to next dimension

    return grad

问题:

我相信它正好起作用，因为np.nditer(x, flags=['multi_index'], op_flags=['readwrite'])直接更新了net.params[param_name]

请确认此理解是否正确