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32- and 64-bit performance
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Date: 2005-03-30 (09:02)
From: Ville-Pertti Keinonen <will@e...>
Subject: Re: [Caml-list] 32- and 64-bit performance
On Wed, 2005-03-30 at 10:41 +0200, Alex Baretta wrote:

> Ah, obviously! But this seems to imply that a 32-bit machine/compiler 
> couple would be generally faster on symbolic processing algorithms, 
> which generally require a good deal of memory allocations/deallocations. 
> Since this is the kind of code which seems to be most idiomatic in 
> Ocaml, I wonder how well or how badly 64 bits will actually impact all 
> our software.

As long as the choice is between i386 and amd64, 64-bit is probably the
way to go; in Jon Harrop's benchmarks, i386 is seldom a win.  Back when
I got my first amd64 machine, I ran some benchmarks that were less
computationally intensive, in which the differences were generally
something like 10-20%.  Which was faster seemed fairly random.

Note that it isn't memory allocation and deallocation that is slower (on
amd64, memory allocation is probably faster, since the allocation
pointer is kept in a register), but programs that use fairly large
amounts of memory.  32-bit vs. 64-bit might be the difference between
everything fitting in L2 or not...