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. 30 000 steps)

• More detail physics?

4

Where is Fluka spending time?Some primary particle create a lot secondaries (105 - 106)

1. Small bug on HMPID: by error someone comment the initialization of the array with the quantum efficiency properties. QEff = 1031 instead of = 1

T0HMPID

Fix on the CVS

5

Where is Fluka spending time?

# Primaries with (transp. time > 30s):

657 (1.1%)

with a total time:

151067 s = 41.9632 h (63.8%)

Transp. time(seg.) Volume name

134101.00 (37.3h) ALIC

6970.29 ZNST

1600.35 ZNSL

1351.01 ZPST

1338.15 QB28

766.762 QF29

650.828 ZPSL

594.577 ZDC

401.73 QBPM

376.511 QS29

192.871 ZNG4

190.431 ZNG3

177.951 ZNG1

177.051 ZNG2

168.76 HUWA

TFluka HIJING Pb-Pb 5.5TeV central event56140 particles(Laptop Centrino 2GHz 1Gb RAM)

Total transport time: 236389s (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 ZNSTZNSL

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

CVS With new volumes

TFluka 65 h 9 h

Geant3 4 h 2 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

3841.32 ZNST

1209.11 ZPST

924.061 ZNSL

818.353 ALIZ

645.909 ZPSL

297.304 ZDC

104.881 ZNG4

103.681 ZNG3

100.791 ZNG2

100.521 ZNG1

53.16 ZNF3

51.78 ZNF4

50.12 ZNF2

49.53 ZNF1

3841.32 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