Re: [Boost-users] [serialization] binary_iarchive performancedegradation with Intel 9.0 compiler

From: Robert Ramey (ramey_at_[hidden])
Date: 2006-06-05 13:07:03

First of - thanks for a very simple example illustrating the problem.  This
has allowed me to say right of the bat that I can't imagine what might be
going on here - thereby saving us all lots of time.

Bill Lear wrote:

> Here is the strange part: When using the Intel compiler, and run with
> the text and xml archive headers commented out, the load method takes
> about 9.6 seconds.  When I uncomment the text and xml headers, the
> load time almost doubles, to 18.8 seconds or so.  I do not see
> this with gcc.
>
> So the question is: have I done something foolish here, or is this
> wacky?

It certainly looks wacky to me.  It would seem that a lot of
code is getting instantiated and invoked even though the archive
is never used.

> I am using the following command to compile the code:
>
> % icpc -O2 -Ob2 -ip <...>
>
> Any help appreciated.

By me as well.

This would require pretty determined sleuthing.  Here are some
suggestions - in no particular order.

How does the size of the executable vary.  It shouldn't - but if
it does that would indicate extra code being instantiated.

Does the linker produce a "map" of some sort - this might
indicate differences in code instantiation.

I'm assuming it compiled for the "appropriate" optimization level.
Lower optimization levels leave in lots of code useful only for
debugging.  This is especially true with templates.

Is there an execution time profiler facilty available which shows
which functions are consuming how much time.  Intel prides
itself on its tools in this area.  That might be very help to
check these out.

Let us know what you find out.

Robert Ramey