Durga,
did you confuse PML and MTL ?
basically, a BTL (Byte Transport Layer ?) is used with "primitive"
interconnects that can only send bytes.
(e.g. if you need to transmit a tagged message, it is up to you
send/recv the tag and manually match the tag on the receiver side so you
can put the message into the right place)
on the other hand, MTL (Message Transport Layer ?) can be used with more
advanced interconnects, that can "natively" send/recv (tagged) messages.
for example, with infiniband, you can use the openib BTL, or the mxm MTL
(note the openib BTL only requires the free ibverbs libraries
and mxm MTL requires proprietary extensions provided by mellanox)
a good starting point is the video Jeff posted at
https://www.open-mpi.org/video/?category=internals
Cheers,
Gilles
On 2/4/2016 2:20 PM, dpchoudh . wrote:
Hi developers
I am trying to add support for a new (proprietary) RDMA capable fabric
to OpenMPI and have the following question:
As I understand, some networks are implemented as a PML framework and
some are implemented as a BTL framework. It seems there is even
overlap as Myrinet seems to exist in both.
My question is: what is the difference between these two frameworks?
When adding support for a new fabric, what factors one should consider
when choosing between one type of framework over the other?
And, with apologies for asking a summary question: is there any kind
of documentation and/or book that explains all the internal details of
the implementation (which looks little like voodoo to a newcomer like
me)?
Thanks for your help.
Durga Choudhury
Life is complex. It has real and imaginary parts.
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