Here is more details on the code and error:
https://groups.google.com/d/msg/theano-users/bNnNHGFRXjs/tk_pB1YdBgAJ
On Tuesday, 23 May 2017 09:54:21 UTC+2, Cinar wrote:
>
> Hello,
>
> I'm facing a similar error and I don't have significant experience with
> scan. When I attempted to solve it with dimshuffle, I get another error
> that I don't expect.
> Any suggestions?
>
> Many thanks.
>
>
>
>
> On Wednesday, 17 February 2016 16:14:11 UTC+1, Dzmitry Bahdanau wrote:
>>
>> Hi all,
>>
>> I have significant experience with theano.scan, but its error messages
>> were always incomprehensible for me. Perhaps this is the day to figure out
>> how to read them..
>>
>> Here is a typical error message that I got this morning:
>>
>>
>> * When compiling the inner function of scan (the function called by scan
>> in each of its iterations) the following error has been encountered: The
>> initial state (`outputs_info` in scan nomenclature) of variable
>> IncSubtensor{Set;:int64:}.0 (argument number 0) has 3 dimension(s), while
>> the corresponding variable in the result of the inner function of scan
>> (`fn`) has 3 dimension(s) (it should be one less than the initial state).
>> For example, if the inner function of scan returns a vector of size d and
>> scan uses the values of the previous time-step, then the initial state in
>> scan should be a matrix of shape (1, d). The first dimension of this matrix
>> corresponds to the number of previous time-steps that scan uses in each of
>> its iterations. In order to solve this issue if the two varialbe currently
>> have the same dimensionality, you can increase the dimensionality of the
>> variable in the initial state of scan by using dimshuffle or shape_padleft.
>> *
>> Now, I know that it means that my "outputs_info" don't match the variable
>> returned by inner scan function. But let me try to read this error message
>> literally:
>>
>>
>>
>> *The initial state (`outputs_info` in scan nomenclature) of variable
>> IncSubtensor{Set;:int64:}.0 (argument number 0) has 3 dimension(s), while
>> the corresponding variable in the result of the inner function of scan
>> (`fn`) has 3 dimension(s)*All right, let's look what we have in
>> outputs_info
>>
>>
>>
>>
>>
>> *ipdb> outputs_info[None, Rebroadcast{0}.0]ipdb> outputs_info[1].ndim2*
>> Oops! First of all, there is no *IncSubtensor{Set;:int64:}.0, *in this
>> list. In addition, there is no variable with 3 dimensions. But let's look
>> further:
>>
>>
>>
>> *For example, if the inner function of scan returns a vector of size d
>> and scan uses the values of the previous time-step, then the initial state
>> in scan should be a matrix of shape (1, d). *While I believe that
>> providing an initial state of shape (1, d) would probably work, nobody does
>> this, including the official scan tutorial! The standard practice in such
>> case is to provide a d-vector as an initial state. In the common case when
>> only previous state results are used, it is perfectly fine to have the
>> initial state and the value returned by scan function with the same shape!
>>
>> This error message gives me a double blow: first it is incomprehensible,
>> second, it postulates that I have always been using Scan in wrong way, and
>> makes me wonder, how it ever worked. The only useful information in this
>> message is that the result of the inner function has 3 dimensions. This was
>> actually helpful in fixing the bug.
>>
>> I would be curious to hear the opinion of Theano developers, can we
>> somehow make this super common error message less confusing?
>>
>
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