On 2/5/14 11:49 PM, "Greg Lindahl" <lind...@pbm.com> wrote:
>In the usual Clos network, 1/2 of the nodes can make a single call to >the other 1/2 of the nodes. That's what's non-blocking. Nothing else >is. Running any real code, every node talks to more than one other >node, and the network is not non-blocking. > >It makes perfect sense in a telephone network. In the real world, a >Clos network is good but not non-blocking. In this case, though, leaving aside multicast, isn't it not so much that the network cannot connect, but that any given node can only "receive" one call at a time, so the blocking is when the second caller tries to call the node when it's "busy" You have N/2 independent paths available (or some equivalent) and that is the most you could possibly use since any path can have only two endpoints. If the nodes are (at some granularity) single threaded, then having multiple interfaces on each node wouldn't help, since the CPU can only talk to one at a time. (Yes, real processors have DMA and so do I/O interfaces, so you can actually have data coming from multiple sources at exactly the same time) Maybe the issue is that *real* codes don't have a single thread on a processor? (even if the multiple parallel threads are things like CPU and DMA I/O devices). > _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
