HSF Generator Meeting, 28 March 2019
Present/Contributors: Andrea Valassi, Josh McFayden, Servesh
Muralidharan, Qiang Li, Frank Siegert, Graeme Stewart, Stephen Jiggins,
ATLAS and CMS event generator accounting update
- Qiang: update on CMS accounting numbers (attached to the agenda):
- Official Numbers from CMS Computing:
- Gen+Sim = 50 sec/ev/core
- Digi: 10 sec/ev/ecore
- Reco: 25 sec/ev/core
- Assume 1 core = 10 HS06, note this introduces a 20% error
- Table 1, CMS:
- Total Events:
- GEN fraction ~7.3% (1.41*0.05 + 1.96*0.17 + 0.43*0.05
- 1.94*0.04 + 0.712*0.05 + 0.154*0.05 + 0.876*0.05 +
1.95*0.05)/9.4, where 0.05, 0.17 and 0.04 are from
numbers achieved from local tests, presented in last
meetings (DY LO MLM 5%, DY NLO 17%, TT powheg 4%, QCD
50to80 Pythia8 <1%)
- Thus GEN -> 85*7.3%=6.2 sec/ev/core (6.2*9.4B=58.3B)
- Qiang: this 7% is GEN as a fraction of MC production, but MC prod
is only ~50% of worldwide CMS computing, so this translates to
GEN being approximately 4%.
- Josh: note that 4% is still lower than the ATLAS number
previously presented, but it is larger than the 1% previously
presented by CMS at the CSRG. On the other hand, there are
also some other small samples missing.
- Josh: will also change the ATLAS numbers to have a closer
- Josh on ATLAS numbers in the other tables.
- Andrea: would be nice now to concentrate on one biggest
consumer, ie sherpa for ATLAS and MG for CMS in V+jets. Josh:
this is exactly what I am trying to do in the next tables in
the document. Table 2 is one V+jets (W→eν+jets@NLO).
- Josh: two columns for sec/evts, to take into account the
generation time with and without filtering. Average 400 sec/event
because many events are thrown away by filtering, while
60sec/event is intrinsic generator speed. Andrea: interesting,
maybe CMS generation is faster also because of a different
- Josh: CPU% adds up to 100% for all rows. It is based on the first
column, not the second.
- Would it be possible to get similar numbers as in Table 2 and 3
for CMS (from local tests?). Qiang: will try to get some numbers
for the next meeting in two weeks.
- Josh on the next section on benchmarking (eg figure 2).
- Josh: we should think of a more meaningful way to present
weight effect than just negative weight distribution. Andrea:
could this be a multiplicative factor, “you have to generate
and simulate 10 times as many events”? Frank: yes a
multiplicative factor is probably what we need, but we need to
convolute all sorts of effects, not just negative weights but
also non-unity weights, so we definitely need to include
- Josh: in figure 4 the difference between blue and yellow is in the
choice of the scale. Efe: please write down the scale choice, so
we can try the same in CMS too. Frank: we should make sure that
green MG and yellow sherpa are comparable.
- Josh to Andrea: any progress in investigating the use of some
machines for benchmarking? Andrea: would help to get a five-line
plan, do we need this one day per week, or one week every few
months, is it bare metal, and so on.
- Graeme: there was a presentation by Junichi about Madgraph on
GPUs. Should invite him along to one of these meetings. Graeme:
will email him and cc the WG convenors.