[SCore-users] Help: Too slow running any program

[Bogdan Costescu]

On Fri, 18 Jul 2003, Huiqun Zhou wrote:

> It even took 2 minutes or more to run the simple examples, hello and
> cpi. Although the results are correct, it seems that it keeps looking
> for something at the begining of the run.

I the beginning of the run the only part affected ? I mean, does it take a 
lot of time before printing the first line of output, but afterwards 
everthing works with normal speed ? What is the load of the nodes when 
this happens ?

> only 3COM card is in use.

With Ethernet hardware, especially with FastEthernet one, care must be
taken that the speed and duplex setting of the switch ports and cards are
in harmony. The best solution is to set both the card (default with the
3c59x driver) and the switch port to autonegotiate/NWAY. Failure to do so 
will provide a link with very high probability of packet loss which 
drastically reduces the maximum data transfer rate that can be obtained as 
packets have to be retransmitted. Obviously, any kind of parallel 
computation that uses such a broken link would be very slow.

-- 
Bogdan Costescu

IWR - Interdisziplinaeres Zentrum fuer Wissenschaftliches Rechnen
Universitaet Heidelberg, INF 368, D-69120 Heidelberg, GERMANY
Telephone: +49 6221 54 8869, Telefax: +49 6221 54 8868
E-mail: Bogdan.Costescu at IWR.Uni-Heidelberg.De