PING – Re: [Patch] Fortran: Handle allocated() with coindexed scalars [PR93834] (was: [PATCH] PR fortran/93834 - [9/10/11/12 Regression] ICE in trans_caf_is_present, at fortran/trans-intrinsic.c:8469)

[Tobias Burnus]

Patch PING – see comment in the follow-up email of the patch email - and
in the email(s) before in that thread.

Tobias

On 07.09.21 16:33, Tobias Burnus wrote:
> Now I actually tested the patch – and fixed some issues.
>
> OK? – It does add support for 'allocated(a[i])' by treating
> it as 'allocated(a)', as 'a' must be collectively allocated
> ("established") on all images of the team.*
>
> 'a[i]' is (probably) an allocatable, following Malcolm in
> answer to my question to the J3-list as linked below.
>
> Tobias
>
> * Ignoring issues related to failed images. It could
> also be handled by fetching 'a' from the remote
> image, but I am not sure that's better in terms of
> handling failed images.
>
> PS:
> On 07.09.21 10:02, Tobias Burnus wrote:
>> Hi Harald,
>>
>> I spend yesterday about two hours with this. Now I am still
>> tired but understand more. I think the confusion between the
>> two of us is due to wording and in which directions the
>> thoughts then go:
>>
>>
>> Talking about coindexed, all of a[i], b[i]%c and c%d[i] are
>> coindexed and there are many constraints like "shall not be
>> a coindexed variable" – which then rejects all of those.
>> That's what I was thinking of.
>>
>> I think your starting point is that while ('a' = allocatable)
>>   a, b%a, c[5]%d(1)%a
>> are ALLOCATABLE, adding a subobject reference such as
>>   a(:), b%a(:,:), c[5]%d(1)%a(:,:,:)
>> makes the variable no longer allocatable.
>> I think that's what you were thinking of.
>>
>> We then both argued along those different lines – which caused
>> the confusion as we both thought we talked about the same.
>>
>>
>> While those cases are clear, the question is whether
>>   a[i] or b%a[i]
>> is allocatable or not – assuming that 'a' is a scalar.
>> (For an array, '(:)' has to appear before the image-selector,
>> which in turn makes it nonallocatable.)
>>
>>
>> I tried to pinpoint the words for this in the standard – and
>> failed. I think I need a "how to read the Fortran standard" 101
>> and some long time actually reading it :-(
>>
>> Malcolm has answered me – and he believes (but only offhand) that
>>   a[i]  and  b%a[i]
>> _are_ allocatable. See (6) at
>> https://mailman.j3-fortran.org/pipermail/j3/2021-September/013322.html
>>
>>
>> This implies that
>>   if ( allocated (a[i]) .and. allocated (b%a[i]) ) stop 1
>> is valid.
>>
>> However, I do note that coarray allocatables have to be collectively
>> (de)allocated, therefore
>>   allocated (a[i]) .and. allocated (b%a[i])
>> is equivalent to
>>   allocated (a) .and. allocated (b%a)
>> at least assuming that no image has failed.
>>
>>
>> First: Does this answer all the questions you had and resolved the
>> confusion?
>> Secondly, do you agree about the last bits of the analysis?
>> Thirdly, what do you think of the attached patch?
>>
>> Tobias
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