Thread Subject: matlab on a dual core

I have a strange phenomenon occurring when using Matlab on a dual
core Dell laptop machine. If I run two Matlab programs with two
Matlab windows open at the same time, each of them runs much faster
(2x or 3x) than if I run a single program with only one Matlab window
open (or, two Matlab windows open but one program being idle). Has
anybody encountered a similar problem?

In article <ef4af5a.-1@webcrossing.raydaftYaTP>, iacoviel@bcnospam.edu
says...
> I have a strange phenomenon occurring when using Matlab on a dual
> core Dell laptop machine. If I run two Matlab programs with two
> Matlab windows open at the same time, each of them runs much faster
> (2x or 3x) than if I run a single program with only one Matlab window
> open (or, two Matlab windows open but one program being idle). Has
> anybody encountered a similar problem?
>
You might be encountering some of the threading limitations of matlab.
You might look at O-Matrix, www.omatrix.com/bench.html, which will take
full advantage of both cores in a single instance of the executable.

Matt wrote:
>
>
> I have a strange phenomenon occurring when using Matlab on a dual
> core Dell laptop machine. If I run two Matlab programs with two
> Matlab windows open at the same time, each of them runs much faster
> (2x or 3x) than if I run a single program with only one Matlab
> window
> open (or, two Matlab windows open but one program being idle). Has
> anybody encountered a similar problem?
  
I cannot reproduce your result with my two processor (Xeon) Dell
Workstation with WinXP + R2006b. On the contrary each process is
about ten percent slower when the other is running.

I used this code for the test:

function cssm( N )
    val = rand( 1e6, 1 );
    while true
        tic
        for n = 1:N
            s1 = sin(val);
        end
        toc
        drawnow
    end
end

/ per

per isakson wrote:
>
>
> Matt wrote:
>>
>>
>> I have a strange phenomenon occurring when using Matlab on a
dual
>> core Dell laptop machine. If I run two Matlab programs with two
>> Matlab windows open at the same time, each of them runs much
> faster
>> (2x or 3x) than if I run a single program with only one Matlab
>> window
>> open (or, two Matlab windows open but one program being idle).
> Has
>> anybody encountered a similar problem?

i have seen strange results due to laptop power settings. newer
laptops can dynamically change processor speed that can cause odd
runtime speed changes. be sure to lock down the speed control on
max, lock hds on so they don't got to sleep, etc, so you can get
consistent speed results on a laptop.

Thanks. Do you know how in Windows I can lock down speed control?

dave wrote:
>
>
> per isakson wrote:
>>
>>
>> Matt wrote:
>>>
>>>
>>> I have a strange phenomenon occurring when using Matlab on
a
> dual
>>> core Dell laptop machine. If I run two Matlab programs with
> two
>>> Matlab windows open at the same time, each of them runs
much
>> faster
>>> (2x or 3x) than if I run a single program with only one
> Matlab
>>> window
>>> open (or, two Matlab windows open but one program being
> idle).
>> Has
>>> anybody encountered a similar problem?
>
> i have seen strange results due to laptop power settings. newer
> laptops can dynamically change processor speed that can cause odd
> runtime speed changes. be sure to lock down the speed control on
> max, lock hds on so they don't got to sleep, etc, so you can get
> consistent speed results on a laptop.

On Thu, 25 Jan 2007 13:18:47 -0500, Matt wrote:
<TOP-posting repaired>
> dave wrote:
>>
>>
>> per isakson wrote:
>>>
>>>
>>> Matt wrote:
>>>>
>>>>
>>>> I have a strange phenomenon occurring when using Matlab on
> a
>> dual
>>>> core Dell laptop machine. If I run two Matlab programs with
>> two
>>>> Matlab windows open at the same time, each of them runs
> much
>>> faster
>>>> (2x or 3x) than if I run a single program with only one
>> Matlab
>>>> window
>>>> open (or, two Matlab windows open but one program being
>> idle).
>>> Has
>>>> anybody encountered a similar problem?
>>
>> i have seen strange results due to laptop power settings. newer
>> laptops can dynamically change processor speed that can cause odd
>> runtime speed changes. be sure to lock down the speed control on
>> max, lock hds on so they don't got to sleep, etc, so you can get
>> consistent speed results on a laptop.

> Thanks. Do you know how in Windows I can lock down speed control?
>

I would assume that this is a BIOS-setting.I think it's called
speed-step technology for intel-based processors?

/PB