[SAGA-RG] SAGA Message API Extension

[Andrei Hutanu]

Hi,

>>
>> 2) I see ordering is enforced, could that be an option?
>
>
> I think ordering is *not* enforced, but I do wonder if it should be  
> an option or a channel property (certainly semireliable will likely  
> result in some reording whereas a TCP channel would enforce ordering  
> of the messages for instance).
>
> This is a controversial topic in the HPC message passing community  
> (whether msg. ordering is a good or bad-thing to enforce in at the  
> hardware level).
>
I was thinking the same (no strong feelings for either option or 
property) but the text tells otherwise :
In 2.1 introduction :
In contrast, this message API extension guarantees that message blocks 
of arbitrary size are delivered in order, and intact, without the need 
for additional application level coordination or synchronization.
and

then in 2.1.7 reliability corectness and ordering
The order of sent messages MUST be preserved by the implementation. 
Global ordering is, however, not guaranteed to be preserved:

Assume three endpoints A, B and C, all connected to each other. If A 
sends two messages [a1, a2], in this order, it is guaranteed that both B 
and C receive the messages in this order [a1, a2]. If, however, A sends 
a message [a1] and then B sends a message [b1], C may receive the 
messages in either order, [a1, b1] or [b1, a1].

Andrei