[mpich-discuss] Why is my quad core slower than cluster

[Scott Atchley]

Darius,

Sorry, I was thinking kernel-to-kernel and not userspace. It should  
not affect userspace-to-userspace.

Scott

On Jul 10, 2008, at 11:22 AM, Darius Buntinas wrote:

>
> But the kernel is not doing the memcpy.  The memcpy used in mpich2  
> for intel x64_64 is from libc.  Scott, do you know if there is a  
> problem with libc memcpy also?
>
> -d
>
> On 07/10/2008 09:00 AM, Scott Atchley wrote:
>> On Jul 8, 2008, at 12:35 PM, zach wrote:
>>> I am using a cluster.
>>> Each pc has two cpus and they are Xeon. Each cpu has 4GB, i think  
>>> red
>>> hat is running.
>>>
>>> I also use a pc at home- quad core intel chip, 8gb ram, ubuntu.
>>>
>>> Both are using mpich.
>>>
>>> I have found that my home pc is only running about 1/3 the speed of
>>> the cluster, and the number of processes (4) and code is the same.
>>>
>>> Can anyone tell me if this is typical, and why, or am I not  
>>> optimizing
>>> something properly?
>>>
>>> Thanks
>>> Zach
>> Which processor (Harpertown?). Which kernel?
>> Kernels <= 2.6.20 use the wrong memory copy routine for Intel Core2  
>> cpus. Since all of your communication will use memory copy, it will  
>> make a difference.
>> Scott
>