Hey,

I am unable to calculate grad_b1, even though my equation seems to be correct, as I have passed all the other unit test except for this one, despite the fact that other equation seems to have a similar format to this one.

Hey,

I am unable to calculate grad_b1, even though my equation seems to be correct, as I have passed all the other unit test except for this one, despite the fact that other equation seems to have a similar format to this one.

Both cases indicate that you incorrectly implemented `grad_b1`

calculation (while other calculations are ok). So please check your `grad_b1`

calculation.

Cheers

I am having the exact same problem / behavior (output numbers for grad_b1 are the same).

I have been up and down the code 1000 times and canâ€™t see what the problem is. As the OP mentioned, grad_b1 is calculated with very similar parts to both grad_W1 and grad_b2, both of which are passing the unit tests in this case.

I even tried pre-calculating the common factors (yhat-y) and (l1 * z1) into their own variables and sharing those variables for the calculations of grad_b1, grad_W1 and grad_b2 just to see if there was something stupid I was doing, but Iâ€™m getting the same result.

Any guidance on this?

(Also, if there any chance that a change has made the unit tests wrong â€“ looks like two identical issues within a week of each other. Just wonderingâ€¦)

thanks in advance!

That is true. In this assignment, to calculate layer 1 parametersâ€™ gradients we use an intermediate variable `l1`

. So if you calculated `grad_W1`

correctly, there should be no problem calculating `grad_b1`

.

It is hard guide why particularly the `grad_b1`

but judging by your comment, you donâ€™t need to multiply `l1`

by `z1`

when calculating `grad_b1`

(similarly as you did in `grad_W1`

calculation).

Cheers

1 Like

@arvyzukai, thank you!

Switching the grad_b1 to just use l1 instead of l1*z1 did the trick.

I believe the figure at the top of Exercise 4 is wrong, then, since it says to use l1*z1 in grad_b1.

1 Like

I agree that the figure is not the most elegant one, but here l1 (the final version of it in calculations) is the **everything inside the bracket**, *not just* the first part.

So when calculating grad_b1, you just have to reduce it with the sum (and I agree that the choice of dot 1^T_m is unintuitive notation to indicate the sum ) (and also the choice of using the \cdot here â€¦ I donâ€™t know, to me it seems not the right notation, but Iâ€™m not the expert here so â€¦)

Cheers

Thank you guys - I was stuck here for 2 hours!

This must be fixed, or at least supplemented with more explanations.

hi , In backprob i have same issue the error come below

Failed default_check.

Expected:

[[ 0.56665733]

[ 0.46268776]

[ 0.1063147 ]

[-0.17481454]

[ 0.11041817]

[ 0.32025188]

[-0.51827161]

[ 0.08430878]

[ 0.19341 ]

[ 0.08339139]

[-0.35949678]

[-0.13053946]

[ 0.19055422]

[ 0.56405985]

[ 0.13321988]],

but got:

[[0.56665733]

[0.46268776]

[0.1063147 ]

[0. ]

[0.11041817]

[0.32025188]

[0. ]

[0.08430878]

[0.19341 ]

[0.08339139]

[0. ]

[0. ]

[0.19055422]

[0.56405985]

[0.13321988]].

Failed default_check.

Expected:

[[ 0.01864644]

[-0.31966546]

[-0.3564441 ]

[-0.31703253]

[-0.26702975]

[ 0.14815984]

[ 0.25794505]

[ 0.24893135]

[ 0.05895103]

[-0.15348205]],

but got:

[[0.01864644]

[0. ]

[0. ]

[0. ]

[0. ]

[0.14815984]

[0.25794505]

[0.24893135]

[0.05895103]

[0. ]].