Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watmath!clyde!cbosgd!ucbvax!ucbcad!ames!hao!gatech!hubcap!ravi From: ravi@hubcap.UUCP Newsgroups: comp.hypercube Subject: Re: Question on hypercube routing Message-ID: <293@hubcap.UUCP> Date: Tue, 14-Jul-87 15:50:48 EDT Article-I.D.: hubcap.293 Posted: Tue Jul 14 15:50:48 1987 Date-Received: Fri, 17-Jul-87 01:34:01 EDT Sender: fpst@hubcap.UUCP Lines: 36 Approved: hypercube@hubcap.clemson.edu In article <291@hubcap.UUCP> wen-king@VLSI.CALTECH.EDU (Wen-King Su) writes: > >In article <285@hubcap.UUCP> ravi@CS.UCLA.EDU writes: ><>The obvious solution to this problem is to randomly choose the direction >>bits that differ instead of scanning from right to left or left to right. > >each message at a randomly chosen bit for that message. > >If you do this, you may have problems with deadlock due to lack of queue >space along the path of the message. One reason for using the routing >algorithm described by pase in his article is that the algorithm is proven >to be deadlock free provided that the destination node will eventually >consumes all messages it receives. This particular routing algorithm is >call the e-cube routing algorithm. I can see the possibility that a message will never reach its destination when it is routed in an arbitrary direction (no longer shortest path routing) instead of a direction towards the destination. A case can be made for doing this in a congested situation when buffers in the chosen direction are full. However when one chooses a direction toward the destination I see no reason why it should deadlock. I would appreciate if you can give us the argument as to why it deadlocks or any references pointing to the deadlock proof. ravi ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ T. M. Ravi UCLA Computer Science Department, 3680 Boelter Hall, UCLA Los Angeles, CA 90024 Phone: (213) 825-2266 ARPA : ravi@CS.UCLA.EDU UUCP : {...sdcrdcf, ihnp4, trwspp, ucbvax}!ucla-cs!ravi ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~