# 2nd prog problem Regularization Week 1 . np.sum(np.square(W1)

Hi,
What am I not understanding about double sums over several indicies???
My solution to L2 Reg is
`L2_regularization_cost = (lambd/(2*m))*(np.sum(np.square(W1))+np.sum(np.square(W2)+np.sum(np.square(W3))))`
I thought a sign was incorrect but that wasn’t it.
These are the shapes of the W3 W2 and W1
(1, 3) (3, 2) (2, 3)

But the checker gives me an error.
Error: Wrong output
1 Tests passed
1 Tests failed

AssertionError Traceback (most recent call last)
in
3 print("cost = " + str(cost))
4
----> 5 compute_cost_with_regularization_test(compute_cost_with_regularization)

~/work/release/W1A2/public_tests.py in compute_cost_with_regularization_test(target)
30 ]
31
—> 32 single_test(test_cases, target)
33
34 def backward_propagation_with_regularization_test(target):

~/work/release/W1A2/test_utils.py in single_test(test_cases, target)
118 print(’\033[92m’, success," Tests passed")
119 print(’\033[91m’, len(test_cases) - success, " Tests failed")
→ 120 raise AssertionError(“Not all tests were passed for {}. Check your equations and avoid using global variables inside the function.”.format(target.name))
121
122 def multiple_test(test_cases, target):

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

It looks like some * signs got trashed because you just “copy/pasted” the code as text. You might want to use the </> tool to define it as “code”, so that it displays correctly. At first glance, the use of np.sum and np.square in your code looks correct, but I think there is a subtle error: your parentheses do not group the terms correctly. You can use the notebook editor to check the matching parens. Look at them carefully and I think you’ll see the error.