Computational resources
The track finding and fitting must run on the D0 reconstruction farm and must be able
to keep up with the data acquisition.
CPU time
Our goal for average reconstruction time is roughly 10 sec/event. This corresponds to
200 processors and a data rate of 20 events/sec. We are near this level for simple events
but expect the addition of missing features to increase the time while continuing optimization
decreases it.
The time is a sensitive function of parameters such as the minimum transverse momentum
and the maximum impact parameter. These may have to be adjusted to meet our goal of
keeping up with the data acquisition.
We might eventually adopt a two-pass strategy where interesting events are selected in the
first pass or more detailed tracking is done in regions of interest (around a calorimeter
cluster or vertex) in a second pass.
Memory
We must also fit in the memory present in the farm machines. At present, this is 256 MB
per processor. The present code is much larger but it appears there is a memory leak.
We do not believe the entire program must fit in the real memory but we understand that
accessing virtual memory will cost CPU time.
D0 Global Tracking Status GCAS March 2000 dladams@uta.edu