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From: Markus Elfring <Markus.Elfring@web.de>
To: Julia Lawall <julia.lawall@lip6.fr>
Cc: Coccinelle <cocci@systeme.lip6.fr>
Subject: Re: [Cocci] Working with pipes for parallel SmPL data processing?
Date: Tue, 11 Jun 2019 09:50:07 +0200
Message-ID: <169696ef-4868-14e7-6afd-f3e4b458fa47@web.de> (raw)
In-Reply-To: <alpine.DEB.2.21.1906102257030.2636@hadrien>



Am 10.06.19 um 23:00 schrieb Julia Lawall:
>
>
> On Sun, 9 Jun 2019, Markus Elfring wrote:
>
>> Hello,
>>
>> The Coccinelle software supports also a variant of parallel data processing
>> after the parameter “--jobs” was passed.
>> https://github.com/coccinelle/coccinelle/blob/7ec31ed1fadf738bc487ccefdc63bfe0598f44cc/docs/manual/spatch_options.tex#L745
>>
>> It is nice when it works to distribute analysis on source files to some processors.
>> Unfortunately, undesirable software behaviour can be observed if a database
>> like “PostgreSQL 11.3-7.1” would be used in such a system configuration.
>> Thus I imagine that it can be occasionally appropriate to perform desired
>> parallel data processing by the usage of a detailed pipeline instead.
>> https://ocaml.github.io/ocamlunix/pipes.html
>>
>> How do you think about another application for this kind of
>> inter-process communication?
>
> When you use -j,

with a value bigger than one


> you fork processes that thus the child processes write to
> a different region of memory than the parent process.

This can be.

But such forked processes have got access also to copied data
from the the parent process.


> I don't have any interest in connecting Coccinelle to a database,

I am curious if any other users of your software can adjust
the corresponding development interests.


> so I'm not going to spend any time on debugging your issue.

I hope that collateral software evolution can happen if more advices
will be taken better into account from existing software documentation.
https://docs.sqlalchemy.org/en/13/core/pooling.html#using-connection-pools-with-multiprocessing


The data storage is working already if known database connections
would be performed only by a single process (instead of background processes).


> Maybe you can use a hashtable,

I would find an other data structure more helpful for the storage
of analysis results from parallel source code processing.


> then use merge in a finalize,

Thanks for such feedback.


> and the write the information to the database in the parent thread.

This is also my software development idea for working with a detailed
process pipeline.


> The use of merge is illustrated in eg tests/merge_vars.cocci

I would about the detail that a test source file is empty here.
https://github.com/coccinelle/coccinelle/commit/0207001b5241092e7b22cf4f99b22db13c01a24d#diff-27862a1fe13b63e871b358e9fc54b3b7

I find the usage of Coccinelle's merge functionality unclear at the moment.
Can such an area become better documented?

Regards,
Markus
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Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-09 17:19 Markus Elfring
2019-06-10 21:00 ` Julia Lawall
2019-06-11  7:50   ` Markus Elfring [this message]

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