[MPICH] Maximum message length

[James S Perrin]

Ashley Pittman wrote:

> On Thu, 2006-01-05 at 12:14 +0000, James S Perrin wrote:
> 
>>Hi,
>>	As the in Sends/Recvs message count is defined as an int (32bit) is the maximum 
>>message count 2^31 or (2^31)/sizeof(datatype) ie the number of bytes is limited 
>>to 2^31 ? Is this behaviour implementation specific?
> 
> 
> This isn't quite right, the maximum count is 2^31 as you say but the
> maximum message size if (2^31)*sizeof(datatype). 

Thanks that answers my question.

> Given that a int is 4
> bytes allows 8Gb transfers, if you want more just use a larger
> datatypes.

No, I need to send messages of any datatype where count > 2^31. Though I could
define a large array of datatype as a new MPI_Type I would think it better to
send the messages in chunks of 2^31 (or less)?

Regards
James
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