HDTenEightyP/NetNews huggingface dataset:
From: anik@crhc.uiuc.edu (Sadun Anik)
Subject: Re: Synchonizing watches
Organization: Center for Reliable and High-Performance Computing
Date: 3 Sep 92 11:14:31

In article <1992Sep3.123226.14205@hubcap.clemson.edu> steve@hubcap.clemson.edu ("Steve" Stevenson) writes:
   [I saw this on sci.logic. I thought it was a nice problem for this group.
     steve]
   >From: dougs@tvnews.tv.tek.com (Doug Stevens)
   >Message-ID: <1992Sep1.234452.26917@tvnews.tv.tek.com>

   [....]

   A and B are two people at two ends of a very slow telephone connection. 
   They are both completely cut off from the world except for their connection 
   with each other.  In particular, they have no idea what time it is in the 
   real world.

   There is a delay AB in the transmission of what is being said by
   A to B, and a delay BA in the transmission of what is being said
   by B to A. The delay AB does not equal the delay BA. The delays, for the
   purpose of this problem, are on the order of minutes in each direction.

   Both A and B have watches. Before they begin to talk, the watches are not
   set to the correct time, nor are they set to the same time.

   The problem is to devise a procedure such that A and B can, via their 
   telephone connection only, accurately synchronize their watches (to
   within a few seconds). The watches do not have to reflect time in the
   real world, but must match each other. Both A and B will know the procedure 
   before the call begins, and each will know whether he is A or B.

   Thanks for any help.
----------------

OK I'll bite. It is trivial for A and B to figure out AB+BA. It is
also trivial for them to synchronize their watches assuming AB=BA (or
any preset assumtion on AB/BA). At this point their watches are
actually synchronized. You can not refute this with any communication
between A and B using this communication channel. My wild guess :) and
please tell me if this is wrong.

[I don't think that your assumptions are safe. Steve]


If you are using a third person "C" to check if their watches are
actually synchronized using delays AC,CA,BC and CB, then the system you
are solving is perturbed so the previous solution doesn't need to be
valid. But this is irrelevant because this is not the system  in the
problem. The solution is not also valid if you have another means of
communication between A and B. 

--
Sadun Anik, U of Illinois at Urbana-Champaign
Center for Reliable and High-performance Computing
e-mail: anik@crhc.uiuc.edu

Newsgroups: comp.parallel
From: bernardl@cs.stanford.edu (Bernard Lee)
Subject: Thanks for your help with our beta-testing!
Keywords: beta-testing, iPSC/DASH library
Organization: CS Dept, Stanford University, CA 94305, USA
Date: Mon, 31 Aug 92 01:07:45 GMT

Most of the bugs on the current release of the iPSC/DASH  library
have  been  identified and fixed. All the C and FORTRAN functions
are now up and running.  As a result, we are  planning  to  leave
the  current  release as it is for now.  Many thanks to those who
have suffered through those bugs in the initial release!   Again,
the library is available via anonymous FTP at:

              36.22.0.120     mojave.stanford.edu

We have received a number of email questions from users who  have
not  yet registered with us.  For a variety of reasons (including
legal ones), we do wish to maintain a complete list of our active
users.  Since  we have shown a certain amount of trust by leaving
our code on an anonymous ftp site, we will very  much  appreciate
your  voluntary co-operation.  Please send us email if you forgot
to let us know that you have a copy, or if  you  forgot  to  tell
your friends to send us e-mail before suggesting them to download
a copy.

The next major release will include socket code that  will  allow
the  library  to  run  on  a  cluster of SGI workstations.  Since
sockets can be a little  dangerous  to  play  with,  we  are  not
planning  to  make  beta release  available through anonymous FTP
sites. If your site is interested in helping out with  our  beta-
testing,  please  reply  via e-mail with some descriptions on the
facilities available at your site.  Thanks very much.




Newsgroups: comp.parallel
From: JPerkins@novell.com (John Perkins)
Subject: AFS Summary
Apparently-To: comp-parallel@uunet.uu.net
Organization: Novell, Inc.
Date: Thu, 27 Aug 1992 15:56:57 GMT

Many thanks to the persons who e-mailed info. on where to find info.
on AFS.  The follow is a summary of information sent to me:

Morris, Satyanarayanan, Conner, Howard, Rosenthal and Smith:
Andrew: A Distributed Personal Computing Environment
Communications of the ACM March 1986, Volume 29, No. 3.

Satyanarayanan:
Scalable, Secure, and Highly Available Distributed File Access
IEEE Computer, May 1990

Satyanarayanan, Kistler, Kumar, Okasaki, Siegel and Steere:
Coda: A Higly Available File System for a Distributed Workstation Environment.
IEEE Trans. Comp. Vol. 39, No. 4, April 1990

Kistler and  Satyanarayanan:
Disconnected Operation in the Coda File System
ACM Trans. Comp. Systems, Vol. 10 No. 1, February 1992.

Sape Mullender:
Distributed Systems, ACM Press, Addison-Wesley, 1989, ISBN 0-201-41660-3
Page 149-188.

Andrew S. Tanenbaum:
Modern Operating Systems, Prentice-Hall, 1992, ISBN 0-13-595752-4
Page 573-578.

--

Try calling Transarc Corporation, they now do all development with AFS. 
Their number is 412-338-4400.

Rick Romero
Computing Services
Carnegie Mellon University

--

hope you have your ACM's ready

comm of ACM, March 1986, vol 29, number 3 pp184-201

acm trans. on comp sys vol 6, number 1, feb 1988, pp 51-81


proc. of the 10th acm symp. on oper sys principles, dec 1985
"the ITC dist. file system"



Newsgroups: comp.parallel
From: leo@nas.nasa.gov (Leo Dagum)
Subject: Re: Synchonizing watches
Apparently-To: comp-parallel@ames.arc.nasa.gov
Organization: NAS, NASA Ames Research Center, Moffett Field, CA
Date: Thu, 3 Sep 92 19:54:44 GMT

In article <1992Sep3.123226.14205@hubcap.clemson.edu> steve@hubcap.clemson.edu ("Steve" Stevenson) writes:
>[I saw this on sci.logic. I thought it was a nice problem for this group.
>  steve]
>>From: dougs@tvnews.tv.tek.com (Doug Stevens)
>>Message-ID: <1992Sep1.234452.26917@tvnews.tv.tek.com>
>
>[....]

Unless I'm missing something, this is fairly straightforward.

1) A zeroes watch, calls B and hangs up.
2) B waits till phone ends ringing then calls A and hangs up.
3) B calls A again and hangs up.
4) A times the first call back, and now knows (AB + BA), when he gets
   the second call back, he now knows BA as well (and therefore AB).
5) A sets his watch back by AB, and calls B
6) B picks up the phone and zeroes his watch, they now have (approximately)
   synchronized watches.
7) Bob's your uncle.


Leo Dagum
NASA Ames Reseach Center

Newsgroups: comp.parallel
From: eugene@nas.nasa.gov (Eugene N. Miya)
Subject: Biblio updated
Organization: Clemson University
Date: Thu, 3 Sep 92 10:47:17 -0700


I assume I have received "final" changes so I have added
those components and others to the biblio.  Long weekend
coming up (useful time to update copies).

--eugene miya, NASA Ames Research Center, eugene@orville.nas.nasa.gov
  Acting Associate Editor, Software and Book Reviews
Second Favorite email message: Returned mail: Cannot send message for 3 days
A Ref: Mathematics and Plausible Reasoning, vol. 1, G. Polya



Newsgroups: comp.parallel
From: samsung!ulowell!crs.cl.msu.edu!rattan@uunet.UU.NET ()
Subject: help in locating a paper from Supercomputing'90
Apparently-To: ulowell!uunet!comp-parallel
Followup-To: rattan@crs.cl.msu.edu
Keywords: hardcopy of a paper, Supercomputing'90
Organization: Michigan State University
Distribution: na
Date: Fri, 4 Sep 92 01:07:43 GMT

I have not been able to locate the following paper (it
was cited by marcoz@cs.cmu.edu -- in this group sometime
back). I would be grateful if some kind soul can send me
a hardcopy the paper by s-mail. Thanks in advance.

"An Optimal Hypercube Direct N-body solver on Connection
 Machine" Brunet, Mesirov, and Edleman; Supercomputing'90,
748-752.

Ishwar Rattan
Computer Science
Central Michigan University
Mt. Pleasant, MI 48859
rattan@crs.cl.msu.edu

Newsgroups: comp.parallel
From: cmp2c@uvacs.cs.Virginia.EDU (Carmen Pancerella)
Subject: Mesh computers?
Originator: cmp2c@palm.cs.Virginia.EDU
Organization: University of Virginia Computer Science Department
Date: Tue, 1 Sep 1992 02:00:38 GMT

If I remember correctly, there was a posted bibliography
on mesh computers and routing on mesh computers that 
appeared here a while ago.

I would appreciate it if someone send me a copy
of this.

Thanks so much!

Carmen Pancerella
cmp2c@virginia.edu 

Newsgroups: comp.parallel
From: martens@python.cis.ohio-state.edu (Jeff Martens)
Subject: EM-4(?) Question
Keywords: interconnect
Organization: Ohio State U. Dept. of Computer Science
Date: Fri, 4 Sep 1992 01:52:11 GMT

In a recent report posted to the net, David Kahaner said that the
interconnect used in one (or all?) of the EM-3/4/5 family is the
"processor omega with deadlock-free mechanism."

What exactly is the processor omega?  Is it similar to the
homogenous circular shuffle (aka single-stage cube, used in the
Man-Yo)?



-- 

-- Jeff (martens@cis.ohio-state.edu)

Newsgroups: comp.parallel
From: adele@tls-cs.cert.fr (Martin Adelantado)
Subject: Neural nets on CM-2
Organization: CERT Toulouse Dept of Computer Science, FRANCE
Date: 4 Sep 92 08:37:09 GMT



    I am researching applications of neural networks models
on the Connection Machine CM-2.

    Information on references, ftp sites, code, etc..., on this
subject, would be greatly appreciated.

    Please email to adele@tls-cs.cert.fr

Thanks,
Martin

Newsgroups: comp.parallel
From: "Magnus Q. Luo" <qyl@cs.strath.ac.uk>
Subject: Re: paper for distributed scheduling
Organization: Comp. Sci. Dept., Strathclyde Univ., Glasgow, Scotland.
Date: 31 Aug 92 13:53:09 GMT


Here are some papers related to distributed constraint satisfaction 
problems, which are the key problems for distributed scheduling.

Peter Burke and Patrick Prosser,
A Distributed Asynchronous System for Predictive and 
Reactive Scheduling, Department of Computer Science, 
University of Strathclyde, AISL-42-89, p. 57, October 1989

Zeev Collin and Rina Dechter,
A Distributed Solution to the Network Consistency Problem,
Israel Institute of Technology, 1990

E. C. Freuder and M. J. Quinn,
Parallelism in algorithms that take advantage of stable sets of
variables to solve constraint satisfaction problems, 
University of New Hampshire, Durham, New Hampshire., Tech. Rep. 85-21, 
1985

Q. Y. Luo and  J. T. Buchanan,
Distributed Tree Search Algorithms for Distributed 
Constraint Satisfaction Problems,
Department of Computer Science, University of Strathclyde,
KEG-2-91, p. 13, May 1991

Q. Y. Luo, P. G. Hendry, J. T. Buchanan,
A Hybrid Algorithm for Distributed Constraint Satisfaction Problems
The European Workshops on Parallel Computing 92, March 1992, SPAIN, p. 10

Q. Y. Luo, P. G. Hendry, J. T. Buchanan,
A New Algorithm for Dynamic Distributed Constraint Satisfaction Problems
Florida Artificial Intelligence Symposium 92, April 92, USA, p. 5 

Makoto Yokoo et al,
Distributed Constraint Satisfaction for DAI Problem,
The 10th International  Workshop for DAI, p. 20, Oct 1990

  Hope it will help.

  Cheers.

Magnus

Magnus Q. Luo, Department of Computer Science,      _                         
University of Strathclyde, Glasgow G1 1XH, UK      |   _  _  _| |      _ |    
qyl@uk.ac.strath.cs  041-552 4400 Ext 2952         |_T|_||_||_| |__|_||_ |< 

Newsgroups: comp.parallel
From: ewilts@galaxy.gov.bc.ca (Ed Wilts)
Subject: C* on MasPar?
News-Moderator: Approval required for posting to comp.parallel
Reply-To: EWILTS@GALAXY.GOV.BC.CA
Organization: BC Systems Corporation
Date: 3 Sep 92 09:43:58 -0700

I've got a user with C* experience on a Connection Machine.  Given that we have
a DECmpp 12000, does anyone know of any efforts to make C* available on the
MasPar platform?

Thanks,
	.../Ed
-- 

Ed Wilts, BC Systems Corp., 4000 Seymour Place, Victoria, B.C., Canada, V8X 4S8
EWilts@Galaxy.Gov.BC.CA   |   Ed.Wilts@BCSystems.Gov.BC.CA   |   (604) 389-3430


Newsgroups: comp.parallel
From: Barry Margolin <barmar@Think.COM>
Subject: Re: Synchonizing watches
Organization: Thinking Machines Corporation, Cambridge MA, USA
Date: Thu, 3 Sep 92 12:07:23 EDT


Take a look at the algorithms in the Network Time Protocol, RFC 1305.  Or
if the specific algorithms aren't a good match, the references (there are
about 60 of them) at the end of the document should be useful.

-- 
Barry Margolin
System Manager, Thinking Machines Corp.

barmar@think.com          {uunet,harvard}!think!barmar


Newsgroups: comp.parallel
From: maniattb@cs.rpi.edu (Bill Maniatty)
Subject: PhD Studies
Apparently-To: comp-parallel@cis.ohio-state.edu
Organization: Clemson University
Date: Thu, 27 Aug 1992 22:56:40 GMT

[There are lots of programs---what do you want? Check in the directory
 pub/parallel/schools on anonymous ftp to hubcap.clemson.edu. I keep a
 list of schools and a blurb about them. ---Steve]

I'm finishing up my M.S. here at R.P.I. and working in applied parallel computing.
I'm interested in going for a PhD. and I need to make sure I find the best
possible match for my PhD program.

Any recommendations?

Bill

-- 
|
|	maniattb@cs.rpi.edu - in real life Bill Maniatty
|

Newsgroups: comp.parallel
From: jpmott%sunspot.nosc.mil@nosc.mil (Jon Mott)
Subject: Request: Feedback from STRAND users
Apparently-To: comp-parallel@ucsd.edu
Summary: STRAND language
Originator: jpmott@sunspot
Keywords: strand88 parallel distributed processing
Organization: Naval Ocean Systems Center, San Diego, CA
Date: Wed, 2 Sep 1992 22:02:01 GMT

Hello - 

	I would appreciate hearing comments from users of the
STRAND88 product, by Strand Software Technologies. Informal
impressions about the product are all that I am looking for
at this time. I am especially interested in hearing about 
how easy it is to configure, manage and merge with existing
code.

	For those who don't know, STRAND is a language specifically
for parallel and distributed applications, on multiple processors,
of various types across a network, etc.

Thanks,
Jon Mott
Universal Computing, San Diego, CA
jpmott@sunspot.nosc.mil
(or universal!jon@ucsd.edu)

Newsgroups: comp.parallel
From: sullivan@cs.rose-hulman.edu (Fred Sullivan)
Subject: shared memory multiprocessors
Apparently-To: comp-parallel@cis.ohio-state.edu
Organization: Rose-Hulman Institute of Technology
Distribution: usa
Date: Wed, 26 Aug 1992 21:45:42 GMT


I am developing an introductory course in parallel computing and will
shortly be writing a proposal for equipment.  I would like like to have a
multiprocessor system which runs Unix with shared memory and some fairly
small number of processors (4?, 8?, 16?).  What is available for < $50,000?
I know that 4 processor Suns are available in that price range, but these
are really designed to be server machines and come with big disks.  What I
would like is something with more processors for less money.  I am not
particularly worried about absolute performance, since the machines would be
used primarily for teaching.


--
Fred Sullivan                           6060 Wabash Avenue
Computer Science Department             Terre Haute, IN  47803
Rose-Hulman Institute of Technology     sullivan@cs.rose-hulman.edu

Newsgroups: comp.parallel
From: martens@python.cis.ohio-state.edu (Jeff Martens)
Subject: Reduced-diameter rings
Organization: Ohio State U. Dept. of Computer Science
Date: Thu, 27 Aug 1992 02:08:34 GMT


Some time ago (ICPP '90?  But I can't find the paper...) I saw a
scheme to reduce the diameter of a ring by adding chords between
selected nodes.  Does anyone:

1) know about a scheme like this, or

2) know of a publication on a scheme like this?

Thanks.
-- 

-- Jeff (martens@cis.ohio-state.edu)

Newsgroups: comp.parallel
From: parallel@netcom.com (B. Mitchell Loebel)
Subject: The PARALLEL Processing Connection
Organization: Netcom - Online Communication Services  (408 241-9760 guest) 
Distribution: usa
Date: Wed, 02 Sep 92 04:42:44 GMT

September 14, 1992 - Meeting notice -- The PARALLEL Processing 
Connection

MasPar - Supercomputing With a SIMD Architecture

The high performance computing world is becoming increasingly focused 
on MIMD based machines;  MasPar believes that the "MIMD hysteria" has 
clouded the real problem, delivering application performance. Their VP of 
Technology and Architecture, Tom Blank, will discuss the applications 
which best utilize the MasPar autonomous SIMD architecture. Tom is 
uniquely qualified to do this; it is our understanding that he was the prime 
developer of the architecture. Too, this will be the first public presentation 
of their new I/O system which provides solid state disk, I/O buffering and a 
shared extended memory with transfer rates up to 1GB/sec. As usual, we 
will explore third party opportunities for our members with MasPar. And 
we will want to know if they are targeting industrial and commercial 
customers for their machine.

The meeting will take place at 7:30PM at Sun Microsystems at 901 East San 
Antonio Road in Mountain View, California. This is just off the southbound 
San Antonio exit of 101; northbound travelers also exit at San Antonio and
take the overpass to the other side of 101.

Please be prompt; as usual, we expect a large attendance; don't be left out or 
left standing. There is a $8 fee for non-members and members are admitted 
free.

-- 
B. Mitchell Loebel                                      parallel@netcom.COM
PARALLEL Processing Connection                                 408-732-9869

Newsgroups: comp.parallel
From: Patrick Surry <pds@epcc.edinburgh.ac.uk>
Subject: Re: Synchonizing watches
Organization: Edinburgh Parallel Computing Centre
Date: 4 Sep 92 13:49:52 GMT


In article <1992Sep3.201917.25468@hubcap.clemson.edu>, mailrus!samsung!ulowell!cs.ulowell.edu!wex@uunet.UU.NET (Paul M. Wexelblat) writes:

> OK A --->B:  "I'm going to say "BONG" as soon as my second hand
> reaches the 12, when you hear the "BONG", start counting seconds
> on your watch out loud.
> 
> A says "BONG" and times AB+BA seconds; at the end of that time the number
> B has reached is the BA delay

I don't think so.  A says "BONG" at t=0.  At t=AB, B hears "BONG" and
starts counting, saying "zero" at t=AB, "one" at t=AB+1, ...
A will hear "zero" at time AB+BA  - there is no way for A to know
what number B has reached because A won't hear it for another BA seconds.

I think the earlier proof that no solution exists looked right.

Patrick

---------------------------------------------------------------------------
 Engineers  think that theory  approximates reality | Mathematicians never
 Physicists think that reality approximates theory  | make the connection
---------------------------------------------------------------------------
 Patrick Surry, JCMB 2254, Edinburgh, Scotland   e||)   Edinburgh Parallel  
 EMail: pds@epcc.ed.ac.uk  Tel: (031) 650-5960   c||c   Computing Centre    
---------------------------------------------------------------------------

Newsgroups: comp.parallel
From: simon@kikel.Berkeley.EDU (B.Simon@frec.bull.fr)
Subject: Parallel device drivers
Keywords: Device driver, SCSI
Reply-To: simon@kikel.Berkeley.EDU (B.Simon@frec.bull.fr)
Organization: BULL SA Echirolles FRANCE
Date: 26 Aug 92 11:36:38 GMT

Hi,

I am looking for any book or publication on parallel
device driver SCSI or others.


Thanks in advance,

Bertrand Simon

B.Simon@frec.bull.fr


__________________________________________________________





Newsgroups: comp.parallel
From: anik@crhc.uiuc.edu (Sadun Anik)
Subject: Re: Synchonizing watches
Organization: Center for Reliable and High-Performance Computing
	<1992Sep3.172657.10929@hubcap.clemson.edu>
Date: 4 Sep 92 12:40:39

In article <1992Sep3.172657.10929@hubcap.clemson.edu> anik@crhc.uiuc.edu (Sadun Anik) writes:

In my reply I said:
>   OK I'll bite. It is trivial for A and B to figure out AB+BA. It is
>   also trivial for them to synchronize their watches assuming AB=BA (or
>   any preset assumtion on AB/BA). At this point their watches are
>   actually synchronized. You can not refute this with any communication
>   between A and B using this communication channel. My wild guess :) and
>   please tell me if this is wrong.

Ed's comment.
   [I don't think that your assumptions are safe. Steve]
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Maybe it was
not clear in the previous paragraph but what I mean is A and B can
assume a value for AB/BA and solve the problem. Because of the nature
of the problem any assumtion is equally valid and would give you a
solution. There is no safety problem here because this is just a
choice for the value of a parameter. This is the case simply because
as far as A and B are concerned their watches will be synchronized,
and they are the only people which count. They can conduct time based
experiments and their results and all their related communication
(over the slow line) will verify this. Of course they are cutoff from
external world so their experiments will be very limited.

My understanding from the comment above is that when with an asumption
like AB/BA=1/3 A and B synchronize their watches, sometime in the
future they will realise that their their assumtion is not correct.
As I said, if this is the case I would really like to know the
algorithm. I don't have formal background in this topic so I
can't prove what I said is correct. 

>   If you are using a third person "C" to check if their watches are
>   actually synchronized using delays AC,CA,BC and CB, then the system you
>   are solving is perturbed so the previous solution doesn't need to be
>   valid. But this is irrelevant because this is not the system  in the
>   problem. The solution is not also valid if you have another means of
>   communication between A and B. 

Even if you observe A and B and see that their watches are not
"actualy" synchronized (A and B don't know anything about this
observer) for A and B their watches are still synchronized. If
the original question addressed the problem of synchronization as far
as the observer is concerned, there shouldn't be any solution. This
follows trivially from the solution above.



--
Sadun Anik, U of Illinois at Urbana-Champaign
Center for Reliable and High-performance Computing
e-mail: anik@crhc.uiuc.edu

Newsgroups: comp.parallel
From: sxl2259@ritvax.isc.rit.edu
Subject: Truing Plus Language
Apparently-To: uunet!comp-parallel
Reply-To: sxl2259@ritvax.isc.rit.edu
Organization: Rochester Institute of Technology
Date: Fri, 4 Sep 1992 14:56:09 GMT

Hi,

I am looking for Turing Plus for concurrent programming. Please tell me where
I can get it if you know about it. Thanks your time.


Bravo.

Newsgroups: comp.parallel
From: lobsang@unixland.natick.ma.us (Michael Levin)
Subject: need help in C* (for Connection Machine)
Organization: Unixland Public Access Unix & Think_Tank BBS
Distribution: usa
Date: Wed, 26 Aug 1992 03:49:01 GMT


   Is anyone out there familiar with the C* language? This is an
extension to C that is used on the Connection Machine parallel
computers. I have a small grant from the PSC for some computer time on
their CM2 machine, but the manuals they sent me are very skimpy on the
details of programming in C*. If anyone knows this language, and is
willing to answer a couple of simple questions, please email to
mlevin@presto.cs.tufts.edu. Thanks in advance.

Mike Levin
-- 
Maine Network Backup

Newsgroups: comp.parallel