ries@Informatik.TU-Muenchen.DE (Bernhard Ries) (06/21/91)
We have an Alliant FX/2800 which has been running for about 6 months.
The configuration is as follows:
Memory Size = 64 Mb
CE-Cache Size = 1024 Kb
User Memory = 48.9 Mb
Paging File = 165.3 Mb
Swapping File = 135.3 Mb
Number of IPs = 1
Number of CEs = 8
Detach/Attach = 5/4
Cluster 0: CE00 CE01 CE04 CE05
We are currently running Concentrix 2800 2.0.04 and use the
following compilers:
FX/C-2800 V1.1.27
fortran , version 1.1.27
In the last couple of months we have experienced a number of
rather nasty problems with the machine:
1) Programs written using the threads package often cause
operating system panics. In one case, a C-program which
used a wrong array index caused a double bus error. Another
example recursively created threads. This also led to a
operating system crash after a while.
2) The compilers (especially the FX/C-Compiler) often crash and
produce core-dumps. In other cases, loop unrolling is not
handled correctly, which leads to completely wrong results
(A simple loop that should print 1,2,3 prints 1,1,2 instead, etc.)
Since this form of loop unrolling can not be disabled individually,
the only way to fix this seems to be to use no optimization
at all.
3) Excessive ethernet-traffic (e.g. starting a big number of
applications that produce a lot of X-Window output) cause
a deadlock. We circumvented this problem by doubling the
buffer space allocated for the ethernet.
4) The speedup which can be achieved with the machine are
disappointing. This applies to applications which use
processor clusters and to explicitly parallel programs which
use threads. One of the main reasons for this seems to
be the lack of cache consistency mechanisms for the i860 caches.
In most cases, programs which use the threads package are
considerably slower than equivalent programs using standard
UNIX processes.
I would like to know if anyone out there has an FX/2800 and has
made similar experiences or if we are just doing everything wrong.ccm@arco.com (Chuck Mosher) (06/26/91)
Bernhard Ries writes: > Subject: Experiences with Alliant FX/2800 > Message-ID: <1991Jun21.104122.9132@Informatik.TU-Muenchen.DE> > Date: 21 Jun 91 10:41:22 GMT > Sender: news@Informatik.TU-Muenchen.DE > Organization: Technische Universitaet Muenchen, Germany > > We have an Alliant FX/2800 which has been running for about 6 months. > The configuration is as follows: > > Memory Size = 64 Mb > CE-Cache Size = 1024 Kb > User Memory = 48.9 Mb > Paging File = 165.3 Mb > Swapping File = 135.3 Mb > Number of IPs = 1 > Number of CEs = 8 > Detach/Attach = 5/4 > Cluster 0: CE00 CE01 CE04 CE05 > > In the last couple of months we have experienced a number of > rather nasty problems with the machine: > > < stuff deleted about panics, core dumps, etc > > > 4) The speedup which can be achieved with the machine are > disappointing. This applies to applications which use > processor clusters and to explicitly parallel programs which > use threads. One of the main reasons for this seems to > be the lack of cache consistency mechanisms for the i860 caches. > In most cases, programs which use the threads package are > considerably slower than equivalent programs using standard > UNIX processes. > > I would like to know if anyone out there has an FX/2800 and has > made similar experiences or if we are just doing everything wrong. > > We have nearly the same configuration here at ARCO. We have had similar problems with peripherals, mainly tapes. Alliant has been pretty good about responding to and resolving our problems. As for parallel speedup, we've had mixed results using the parallelizing compilers, but very good results using a distributed memory model and message passing. This gets around the cache problems. -- ----+----1----+----2----+----3----+----4----+----5----+----6----+----7-- | Chuck Mosher | Internet : ccm@arco.com | Who needs an editor | | ARCO, Plano, TX | Telephone: (214)754-6468 | when you have ISPF? | ************************************************************************