| Geant4 Cross Reference |
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4 Geant4 - an Object-Oriented Toolkit for S 4 Geant4 - an Object-Oriented Toolkit for Simulation in HEP
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6 6
7 Tips how to run an example in multi-th 7 Tips how to run an example in multi-threading mode
8 -------------------------------------- 8 --------------------------------------------------
9 9
10 Only migrated examples or user applications c 10 Only migrated examples or user applications can be run in multi-threading (MT) mode.
11 The instructions for migrating user applicati 11 The instructions for migrating user applications can be found in Geant4 documentation guides
12 and a short howto is available here: 12 and a short howto is available here:
13 13
14 https://twiki.cern.ch/twiki/bin/view/Geant4/Q 14 https://twiki.cern.ch/twiki/bin/view/Geant4/QuickMigrationGuideForGeant4V10
15 15
16 In this file, we give just useful tips for ru 16 In this file, we give just useful tips for running already migrated examples
17 (or user applications). 17 (or user applications).
18 18
19 1) RUN EXAMPLE IN MULTI-THREADING MODE 19 1) RUN EXAMPLE IN MULTI-THREADING MODE
20 20
21 No special steps are needed to build an examp << 21 No special steps are needed to build an example in multi-threading mode.
22 The examples which has been migrated to multi 22 The examples which has been migrated to multi-threading will automatically
23 run in MT when they are built against the Gea 23 run in MT when they are built against the Geant4 libraries built with MT mode
24 activated, otherwise they will run in sequent 24 activated, otherwise they will run in sequential mode.
25 Not migrated examples will run in sequential 25 Not migrated examples will run in sequential mode even when built against
26 Geant4 libraries built with MT mode activated 26 Geant4 libraries built with MT mode activated.
27 27
28 The examples which do NOT support MT can be e << 28 The examples which support MT can be easily recognized by the following lines
29 of code in main (): 29 of code in main ():
30 30
>> 31 #ifdef G4MULTITHREADED
>> 32 G4MTRunManager* runManager = new G4MTRunManager;
>> 33 #else
31 G4RunManager* runManager = new G4RunManager 34 G4RunManager* runManager = new G4RunManager;
>> 35 #endif
32 36
33 or << 37 The compiler flag -DG4MULTITHREADED is automatically set when building applications
34 << 38 using Geant4's CMake (via GEANT4_USE_FILE) and GNUmake systems, and is listed in
35 auto* runManager = G4RunManagerFactory::Cre << 39 the flags reported by the --cflags option of the geant4-config program.
36 40
37 2) SET NUMBER OF THREADS 41 2) SET NUMBER OF THREADS
38 42
39 When the number of threads is not selected in 43 When the number of threads is not selected in the application, the default number
40 (which is actually 2) will be used. Another n 44 (which is actually 2) will be used. Another number of threads can be set in several
41 ways: 45 ways:
42 46
43 - in the code 47 - in the code
44 48
45 auto* runManager = ...; << 49 #ifdef G4MULTITHREADED
46 runManager->SetNumberOfThreads(4); << 50 G4MTRunManager* runManager = new G4MTRunManager;
>> 51 runManager->SetNumberOfThreads(4);
>> 52 #else
>> 53 ...
47 54
48 - in a macro file via UI command added just b 55 - in a macro file via UI command added just before /run/initialize
49 56
50 /run/numberOfThreads 4 57 /run/numberOfThreads 4
51 58
52 - by setting the environment variable 59 - by setting the environment variable
53 60
54 export G4FORCENUMBEROFTHREADS = 4 61 export G4FORCENUMBEROFTHREADS = 4
55 or 62 or
56 setenv G4FORCENUMBEROFTHREADS 4 63 setenv G4FORCENUMBEROFTHREADS 4
57 64
58 The environment variable value is forced and 65 The environment variable value is forced and it cannot be changed from a code
59 call or a macro. A warning is issued in such 66 call or a macro. A warning is issued in such situation.
60 67
61 3) OUTPUT FROM THREADS 68 3) OUTPUT FROM THREADS
62 69
63 In MT processing each worker produces its out 70 In MT processing each worker produces its output and these messages are interlayed
64 on the screen. The messeges from threads are 71 on the screen. The messeges from threads are preceded with a predefined string
65 G4WTi> where i is the thread number. Users c 72 G4WTi> where i is the thread number. Users can change this default behaviour
66 and choose 73 and choose
67 74
>> 75 - to buffer the output from each thread at a time, so that the output of each
>> 76 thread is grouped and printed at the end of the job
>> 77
>> 78 /control/cout/useBuffer true|false
>> 79
68 - to limit the output from threads to one sel 80 - to limit the output from threads to one selected thread only:
69 81
70 /control/cout/ignoreThreadsExcept 0 82 /control/cout/ignoreThreadsExcept 0
71 83
72 - to redirect the output from threads in a fi 84 - to redirect the output from threads in a file:
73 85
74 /control/cout/setCoutFile coutFileName 86 /control/cout/setCoutFile coutFileName
75 /control/cout/setCerrFile cerrFileName 87 /control/cout/setCerrFile cerrFileName
76 <<
77 - to buffer the output from each thread at a <<
78 thread is grouped and printed at the end of <<
79 <<
80 /control/cout/useBuffer true|false <<