def affine_forward(x, w, b): out = None # Reshape x into rows N = x.shape[0] x_row = x.reshape(N, -1) # (N,D) -1表示不知道多少列,指定行,就能算出列 = 2 * 32 * 16 * 16/2 = 8192 out = np.dot(x_row, w) + b # (N,M) 2*8192 8192*100 =>2 * 100 cache = (x, w, b) return out, cache,如何改为适用于mnist的矩阵
时间: 2023-11-16 10:06:53 浏览: 31
如果你想将这个`affine_forward`函数应用到MNIST数据集上,你需要将输入的形状从`(N, 2*32*16*16/2)`改为`(N, 784)`,因为MNIST数据集的每张图片的大小是28x28,展开成一维向量后有784个元素。同时,你需要将权重矩阵`w`的形状从`(2*32*16*16/2, M)`改为`(784, M)`。具体的代码实现如下:
```python
def affine_forward(x, w, b):
out = None
# Reshape x into rows
N = x.shape[0]
x_row = x.reshape(N, -1) # (N,784)
out = np.dot(x_row, w) + b # (N,M)
cache = (x, w, b)
return out, cache
```
在这个代码中,我们将输入的形状从`(N, 2*32*16*16/2)`改为`(N, 784)`,并将权重矩阵`w`的形状从`(2*32*16*16/2, M)`改为`(784, M)`。这样,你就可以将这个函数应用到MNIST数据集上了。
相关问题
def affine_forward(x, w, b): out = None # Reshape x into rows N = x.shape[0] x_row = x.reshape(N, -1) # (N,784) out = np.dot(x_row, w) + b # (N,M) cache = (x, w, b) return out, cacheshapes (40,6272) and (8192,100) not aligned: 6272 (dim 1) != 8192 (dim 0)报错
根据你提供的代码,错误可能在于你的权重矩阵和偏置项矩阵的维度不匹配。在这个具体的例子中,权重矩阵 w 的维度为 (6272, 8192),而偏置项矩阵 b 的维度为 (100,),这意味着你需要将偏置项矩阵 b 扩展为一个维度为 (1, 100) 的矩阵,然后将其加到 np.dot(x_row, w) 的结果上。你可以尝试以下代码:
```python
def affine_forward(x, w, b):
out = None
# Reshape x into rows
N = x.shape[0]
x_row = x.reshape(N, -1) # (N, 6272)
out = np.dot(x_row, w) + b.reshape(1, -1) # (N, 100)
cache = (x, w, b)
return out, cache
```
这应该可以解决报错问题。
def affine_forward(x, w, b): out = None N = x.shape[0] x_row = x.reshape(N, -1) out = np.dot(x_row, w) + b.reshape(1, -1) cache = (x, w, b) return out, cache,W为超参数会导致程序错误,应该如何修改
如果W是超参数,则应该在函数外部定义并传递给函数。你可以修改函数定义,使其接受额外的W参数,如下所示:
```
def affine_forward(x, w, b, W):
out = None
N = x.shape[0]
x_row = x.reshape(N, -1)
out = np.dot(x_row, W) + b.reshape(1, -1)
cache = (x, W, b)
return out, cache
```
在调用函数时,你需要将W作为参数传递给函数。例如:
```
W = np.random.randn(784, 100)
out, cache = affine_forward(x, w, b, W)
```
这样,你就可以在函数内部使用超参数W,而不会出现错误。
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