Re: "ocaml_beginners"::[] speed of 32 bit versus 64 installations

Your code seems to do 64-bit integer calculations. The register-size is 
64 bit on x64 but 32 bit on x86.
This means that arithmetic operations on 64 bit integers can be done in 
a single step (more or less) on x64.
On x86 the code must handle things like carry over in software, thus 
requiring multiple steps for 64-bit arithmetic.
In general x64 code is faster than x86, but can also be slower e.g. due 
to the increased pointer size.

I don't know about the state of available (x64) ocaml packages for 
Ubuntu or Windows.

regards
Markus

On 2015-01-25 23:28, [email protected] [ocaml_beginners] wrote:
> Consider the following program:
> http://codeforces.com/contest/498/submission/9305810
>
> I'm running it on this input:
> 100000 100000 100000 100000 100000 100000 100000
>
> I'm testing it on three machines:
>
> A: 2008 macbook pro
>    2.4GHz Intel Core 2 Duo
>    running ocaml 4.01.0, in 64-bits
>
> B: An ubuntu Desktop.  /proc/cpuinfo gives:
>    vendor_id       : GenuineIntel
>    cpu family      : 6
>    model           : 23
>    model name      : Intel(R) Core(TM)2 Quad CPU    Q9550  @ 2.83GHz
>    running ocaml 4.01.0, in 32-bits
>
> C: A very new high-powered machine running wndows server.
>    (I don't have the exact details. This is the machine running on
>    the codeforces server.)
>    running ocaml 4.00.1, in 32-bits
>
> Here are the results:
>
>    A: 1.08 seconds
>    B: 2.95 seconds
>    C: over 3 seconds
>
> I believe that machines B and C are newer and at least as fast as
> machine A.  Yet machine A solves this problem three times faster.  
> The
> conclusion is that the 64 bit installation of ocaml is MUCH faster 
> (at
> least three times as fast) as the 32 bit installation. (On this
> program anyway.)
>
> Which leads to the question: Is there a precompiled package to 
> install
> the 64 bit version on Ubuntu?  On Windows?  It seems kind of 
> important.
>
> Another question.  The ocaml version on try.ocamlpro.com has 32-bit
> integers.  max_int is 2147483647.  I've never seen a release of ocaml
> with 32 bit integers.  Normally it is 31 bits or 63 bits.  What 
> gives?
> Thanks.
>
>                           Danny Sleator

-- 
Markus Weißmann, M.Sc.
Technische Universität München
Institut für Informatik
Boltzmannstr. 3
D-85748 Garching
Germany
http://wwwknoll.in.tum.de/