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32- and 64-bit performance
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Date: 2005-03-30 (12:52)
From: Jon Harrop <jon@f...>
Subject: Re: [Caml-list] 32- and 64-bit performance
On Wednesday 30 March 2005 10:01, Ville-Pertti Keinonen wrote:
> Back when I got my first amd64 machine...


> 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...

Yes. I was thinking that the GC would be slower due to worse cache use in 
64-bit. I used the phrase "de/allocation" as I was applying it to both C++ 
and OCaml.

This raises the question of exactly which OCaml types incur 64-bit quantities 
in the run-time. My guess:

  int (d'oh)
  constant (polymorphic) variant constructor?
  non-constant (polymorphic) variant constructor
  records (except those with all-float fields)

But isn't there quite a low limit on the number of constant variant type 
constructors allowed? So maybe they're squeezed into something a little 

Dr Jon D Harrop, Flying Frog Consultancy Ltd.
Objective CAML for Scientists