Re: [Boost-users] Building boost faster: /MP

Subject: Re: [Boost-users] Building boost faster: /MP
From: Robert Dailey (rcdailey_at_[hidden])
Date: 2009-07-15 15:46:28

On Wed, Jul 15, 2009 at 2:26 PM, Igor R <boost.lists_at_[hidden]> wrote:

> > If this is a compiler flag, then can you try full build with
> >
> >        cxxflags=-MP
> >
> > and then without and report the timings? If this is a magic way to make
> > builds faster, it can be enabled by default.
>
> It is a compiler flag, and it really improves build times in milticore
> environment, but it's somewhat limited:
> http://msdn.microsoft.com/en-us/library/bb385193.aspx

Yes, it is limited in that it does not support a couple of other flags
simultaneously.

However, if you think about it, /MP is a replacement of /Gm (Incremental
Build) and /Yc (Precompiled Headers). When you can build 4 or 8 source files
simultaneously, that's a lot better than these two features, which do not
speed up the build quite as much as this feature does. Additionally, this
feature provides an increase in build speed without the disadvantages of
using PCH and other alternatives.

I think that /MP should be made a default, but give the user the ability to
disable it JUST in case they need to use any of the documented incompatible
language features. That's just my two cents.