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From: Richard Graham (rlgraham_at_[hidden])
Date: 2007-08-13 14:00:03


On 8/13/07 12:34 PM, "Galen Shipman" <gshipman_at_[hidden]> wrote:

>>>>>
>>>> Ok here is the numbers on my machines:
>>>> 0 bytes
>>>> mvapich with header caching: 1.56
>>>> mvapich without header caching: 1.79
>>>> ompi 1.2: 1.59
>>>>
>>>> So on zero bytes ompi not so bad. Also we can see that header
>>>> caching
>>>> decrease the mvapich latency on 0.23
>>>>
>>>> 1 bytes
>>>> mvapich with header caching: 1.58
>>>> mvapich without header caching: 1.83
>>>> ompi 1.2: 1.73
>
>
> Is this just convertor initialization cost?

Last night I measured the cost of the convertor initialization in ob1 on my
dual processor mac, using ompi-tests/simple/ping/mpi-ping, and it costs 0.02
to 0.03 microseconds. To be specific, I commented out the check for 0 byte
message size, and the latency went up from about 0.59 usec (this is with
modified code in tmp/latency) to about 0.62 usec.

Rich

>
> - Galen
>
>>>>
>>>> And here ompi make some latency jump.
>>>>
>>>> In mvapich the header caching decrease the header size from
>>>> 56bytes to
>>>> 12bytes.
>>>> What is the header size (pml + btl) in ompi ?
>>>
>>> The match header size is 16 bytes, so it looks like ours is already
>>> optimized ...
>> So for 0 bytes message we are sending only 16bytes on the wire , is it
>> correct ?
>>
>>
>> Pasha.
>>>
>>> george.
>>>
>>>>
>>>> Pasha
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>>>
>>>
>>
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