Re: [boost] RFC - Updated MapReduce library

Subject: Re: [boost] RFC - Updated MapReduce library
From: Craig Henderson (cdm.henderson_at_[hidden])
Date: 2009-08-29 13:46:06

From: boost-bounces_at_[hidden] [mailto:boost-bounces_at_[hidden]]
On Behalf Of joel
On 09 August 2009 17:32, joel wrote:
> Craig Henderson wrote: 
> > I think we're misunderstanding each other. My point is that if it is an 
> > instance of a functor, then the developer may be tempted to presume a
state 
> > of the object and store instance data. This is invalid as the map task 
> > object is created, used and then destroyed. Any attempt to share data 
> > between map objects breaks the MapReduce design and scalability
properties 
> > (which need to be preserved for loyalty to the MapReduce paradigm and
for 
> > future multi-machine scalability). 
> >   
>
> Well that's a problem with any kind of functor anyway. There is the same 
> problem with Boost.Thread where you should be aware of the internal copy 
> of the functor object etc... 

I've thought about this a lot, and have concluded that a regular functor
*is* more intuitive as it is consistent with other libraries. To that end,
I've updated the sandbox with the code changes in the library and
sample/test applications as well as the documentation

To all users of the library; PLEASE NOTE the Breaking change: map_task and
reduce_task now must implement a function operator rather than static
methods map and reduce. The functor signatures are the same the previous
static methods.

Thanks
-- Craig
http://www.craighenderson.co.uk