Re: problem with parallelism feature example in documentation

From: Vladimir Prus (ghost_at_[hidden])
Date: 2004-11-29 04:17:11

Toon Knapen wrote:

> 
> Vladimir Prus wrote:
>> On Friday 26 November 2004 19:54, Toon Knapen wrote:
>> 
>> 
>>>I'm pretty sure you added the <parallelism> feature example after a
>>>similar question from me;-) Only now I start to really understand the
>>>power of this and how to do it. So I tried it but bjam tells me that I
>>>have a recursivity problem and have no idea why.
>> 
>> 
>> Hi Toon,
>> after looking at the testcase you actually provided (as opposed to some
>> other archive), I understand the problem better.
>> You define libmpi which happens to be built with <parallelism>mpi, which
>> is expanded to reference to libmpi, so libmpi is built again, giving the
>> error.
> 
> I don't understand that. My Jamfile explicitly requests explicitly the
> libmpi with <parallelism>none in following line, right ?
> 
> feature.compose <parallelism>mpi :
> <library>/user-config//libmpi/<parallelism>none ;

That's right, but when you invoke bjam it tries to build all targets with
the default values of properties. For <parallelism> that's "mpi"

1. "libmpi" is built with <parallelism>mpi
2. <parallelism>mpi is expanded to
<library>/user-config//libmpi/<parallelism>none.
3. An attempt to build /user-config//libmpi/<parallelism>none is made, at
which point a recursion cycle is detected.

- Volodya