# Error in conv_forward function

Hello.

I got this error in exercise 3

## Z’s mean = nan

IndexError Traceback (most recent call last)
in
8 Z, cache_conv = conv_forward(A_prev, W, b, hparameters)
9 print(“Z’s mean =\n”, np.mean(Z))
—> 10 print(“Z[0,2,1] =\n”, Z[0, 2, 1])
11 print(“cache_conv[0][1][2][3] =\n”, cache_conv[0][1][2][3])
12

IndexError: index 2 is out of bounds for axis 1 with size 0

Can anyone help me to solve the problem?

Hi Lilit.Ghalachyan,

The error indicates that you do not calculate Z correctly, so its mean cannot be calculated and it cannot be indexed into.

So you need to look at your code and see whether you initialize Z and calculate its value correctly.

I wrote for Z
Z = np.zeros((m, n_H, n_W, n_C))

and also

for c in range(n_C):
weights=W[:,:,:,c]
biases =b[:,:,:,c]
Z[i, h, w, c] = conv_single_step(a_slice_prev, weights, biases)

Can not find the mistake.

I also made some corrections and got this error.

## Z’s mean = 0.2999719807951914 Z[0,2,1] = [ 3.07229898 -2.60921766 -1.63280904 5.71720329 1.18903119 0.90610057 9.2941049 5.13892311] cache_conv[0][1][2][3] = [-1.1191154 1.9560789 -0.3264995 -1.34267579] (2, 13, 15, 8) Error: Wrong output for variable in position 0. 2 Tests passed 1 Tests failed

AssertionError Traceback (most recent call last)
in
11 print(“cache_conv[0][1][2][3] =\n”, cache_conv[0][1][2][3])
12
—> 13 conv_forward_test(conv_forward)

~/work/release/W1A1/public_tests.py in conv_forward_test(target)
118 ]
119
→ 120 multiple_test(test_cases, target)
121
122

~/work/release/W1A1/test_utils.py in multiple_test(test_cases, target)
151 print(’\033[91m’, len(test_cases) - success, " Tests failed")
152 raise AssertionError(
→ 153 “Not all tests were passed for {}. Check your equations and avoid using global variables inside the function.”.format(target.name))

AssertionError: Not all tests were passed for conv_forward. Check your equations and avoid using global variables inside the function.

I have just solved my problem, thank you.

can you please tell how you have sloved?