1 Speed up ALICE simulation with TFluka Ernesto Lopez Torres

2 Problem HIJING Central event takes ~ 60 h with TFluka ~ 4 h with Geant3

3 Why TFluka takes so long time? First ideas: Energy transport cuts on region basics is not allow for hadrons, so we have 1MeV cut for all volumes There is not cut on number of track steps (for GEANT we have set max steps) More detail physics?

4 Where is Fluka spending time? Some primary particle create a lot secondaries ( ) 1.Small bug on HMPID: by error someone comment the initialization of the array with the quantum efficiency properties. QEff = instead of = 1 T0 HMPID Fix on the CVS

5 Where is Fluka spending time? # Primaries with (transp. time > 30s): 657 (1.1%) with a total time: s = h (63.8%) Transp. time(seg.)Volume name (37.3h) ALIC ZNST ZNSL ZPST QB QF ZPSL ZDC QBPM QS ZNG ZNG ZNG ZNG HUWA TFluka HIJING Pb-Pb 5.5TeV central event particles (Laptop Centrino 2GHz 1Gb RAM) Total transport time: s (65.6 h)

6 Where is Fluka spending time? Small hadronic cut (1MeV) on ZDC calorimeter (PIPE, etc) allow the develop of detail hadronic showers. Those hadrons escape the volume and develop the EM part also in ALIC from AliZDCv2::CreateMaterials() // Thresholds for showering in the ZDCs i = 1; //tantalum gMC->Gstpar(idtmed[i], "CUTGAM",.001); gMC->Gstpar(idtmed[i], "CUTELE",.001); gMC->Gstpar(idtmed[i], "CUTNEU",.01); gMC->Gstpar(idtmed[i], "CUTHAD",.01); …… i = 5; //lead gMC->Gstpar(idtmed[i], "CUTGAM",.001); gMC->Gstpar(idtmed[i], "CUTELE",.001); gMC->Gstpar(idtmed[i], "CUTNEU",.01); gMC->Gstpar(idtmed[i], "CUTHAD",.01); …. // Avoid too detailed showering along the beam line i = 7; //iron with energy loss (ZIRON) gMC->Gstpar(idtmed[i], "CUTGAM",.1); gMC->Gstpar(idtmed[i], "CUTELE",.1); gMC->Gstpar(idtmed[i], "CUTNEU", 1.); gMC->Gstpar(idtmed[i], "CUTHAD", 1.);

7 Where is Fluka spending time? ZDC (ZEM), PIPE, Compensator DIPO =>ALIC AliMC::Stepping() timer.Stop() TH3F->Fill(x,y,z,timer.CpuTime());... timer.Start() } T0 ZEM

8 Where is Fluka spending time? (ZDC (ZEM), PIPE, Compensator DIPO) ->ALIC 1100 cm ALIC pi- P=92Gev #secondaries=17626 transport time=134s (2.3 min)

9 Where is Fluka spending time? ZDC and PIPE => ALIC TH3F->Fill(x,y,z,timer.CpuTime()); ZDC ZNST ZNSL ZPST

10 Where is Fluka spending time? ZDC and PIPE -> ALIC

11 To reduce the transport time in ALIC we introduced new volumes with high Energy cuts for gammas an electrons (0.1GeV) ALIC ALIZ Shielding around dipole compensator DCAR PIAR

12 We change from to

13 Final Results CVSWith new volumes TFluka65 h9 h Geant34 h2 h # Primaries with (transp. time > 30s): 33 (0.05%) with a total time: 8497 s = 2.3 h (25.5%) Transp. time(seg.) Volume name ZNST ZPST ZNSL ALIZ ZPSL ZDC ZNG ZNG ZNG ZNG ZNF ZNF ZNF ZNF ZNST

14 TODO Check how the changes could affect the ZDC performance.

15 END

16 Where is Fluka spending time? ALIC ZDC

17 Final FLUKA GEANT