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| 2 | <TITLE> |
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| 3 | </TITLE> |
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| 4 | |
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| 5 | <BODY> |
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| 6 | <TABLE WIDTH="100%"><TR> |
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| 7 | <TD> |
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| 8 | |
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| 9 | |
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| 10 | <A HREF="index.html"> |
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| 11 | <IMG SRC="../../../../resources/html/IconsGIF/Contents.gif" ALT="Contents"></A> |
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| 12 | <A> |
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| 13 | <IMG SRC="../../../../resources/html/IconsGIF/PreviousGR.gif" ALT="Previous"></A> |
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| 14 | <A HREF="histogramming.html"> |
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| 16 | </TD> |
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| 17 | <TD ALIGN="Right"> |
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| 18 | <FONT SIZE="-1" COLOR="#238E23"> |
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| 19 | <B>Geant4 User's Guide</B> |
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| 20 | <BR> |
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| 21 | <B>For Application Developers</B> |
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| 22 | <BR> |
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| 23 | <B>Appendix</B> |
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| 24 | </FONT> |
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| 25 | </TD> |
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| 26 | </TR></TABLE> |
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| 27 | <BR><BR> |
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| 28 | |
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| 29 | <P ALIGN="Center"> |
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| 30 | <FONT SIZE="+3" COLOR="#238E23"> |
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| 31 | <A name="10.1"> |
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| 32 | <B>10.1 Tips for Program Compilation</B></A> |
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| 33 | </FONT> |
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| 34 | <BR><BR> |
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| 35 | |
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| 36 | <HR ALIGN="Center" SIZE="7%"> |
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| 37 | <BR><BR> |
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| 38 | |
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| 39 | <!-- ============================================== Section --> |
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| 40 | |
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| 41 | This section is dedicated to illustrate and justify some of the options |
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| 42 | used and fixed by default in the compilation of the Geant4 toolkit. It |
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| 43 | is also meant to be a simple guide for the user/installer to avoid or |
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| 44 | overcome problems which may occur on some compilers. Solutions proposed |
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| 45 | here are based on the experience gained while porting the Geant4 code |
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| 46 | to different architectures/compilers and are specific to the OS's and |
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| 47 | compiler's version valid at the current time of writing of this manual. |
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| 48 | <P> |
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| 49 | It's well known that each compiler adopts its own internal techniques |
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| 50 | to produce the object code, which in the end might be more or less |
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| 51 | perfomant and more or less optimised, depending on several factors also |
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| 52 | related to the system architecture which it applies to. A peculiarity |
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| 53 | of C++ compilers nowadays is the way templated instances are treated |
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| 54 | during the compilation/linkage process. Some C++ compilers need to |
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| 55 | store temporarily template instantiation files (object files or |
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| 56 | temporary source code files) in a "template repository" or directory |
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| 57 | that can be specified as unique or not directly from the compilation |
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| 58 | command (probably historically coming from the old cfront-based |
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| 59 | implementation of the C++ compiler). |
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| 60 | <P> |
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| 61 | After the installation of the libraries, we strongly suggest to always |
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| 62 | distinguish between the installation directory (identified by $G4INSTALL) |
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| 63 | and the working directory (identified by $G4WORKDIR), in order not to |
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| 64 | alter the installation area for the template repository. |
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| 65 | <P> |
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| 66 | In Geant4, the path to the template repository (for those compilers which |
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| 67 | make use of it) is specified by the environment variable $G4TREP, which |
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| 68 | is fixed and points by default to |
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| 69 | <KBD>$G4WORKDIR/tmp/$G4SYSTEM/g4.ptrepository/</KBD>, where |
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| 70 | <KBD>$G4SYSTEM</KBD> identifies the system-architecture/compiler |
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| 71 | currently used and <KBD>$G4WORKDIR</KBD> is the |
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| 72 | path to the user working directory for Geant4. |
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| 73 | <P> |
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| 74 | A secondary template repository <KBD>$G4TREP/exec</KBD> is created by |
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| 75 | default and |
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| 76 | can be used when building executables to isolate the main repository |
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| 77 | used for building the libraries in case of clashes provoked by |
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| 78 | conflicting class-names. This secondary template repository can be |
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| 79 | activated by defining in the environment (or in the GNUmakefile related |
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| 80 | to the test/example to be built) the flag <KBD>G4EXEC_BUILD</KBD>; |
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| 81 | once activated, the secondary repository will become the read/write one, |
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| 82 | while the primary repository will be considered read-only. |
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| 83 | <P> |
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| 84 | At the current time, only few compilers still make use of a template |
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| 85 | repository. A good recommendation valid in general such compilers is to |
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| 86 | make use of a single template repository (specified by the |
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| 87 | <KBD>$G4TREP</KBD> environment variable) for building all Geant4 libraries; |
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| 88 | then use a secondary template repository (<KBD>$G4TREP/exec</KBD>, together |
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| 89 | with the <KBD>$G4EXEC_BUILD</KBD> flag) |
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| 90 | when building any kind of example or application.<BR> |
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| 91 | It's always good practise to clean-up the secondary template repository |
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| 92 | from time to time. |
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| 93 | |
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| 94 | <HR> |
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| 95 | <A name="10.1.3"> |
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| 96 | <H2>10.1.3 Sun</H2></A> |
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| 97 | <P> |
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| 98 | OS: SunOS<BR> |
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| 99 | Compiler: CC<BR> |
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| 100 | <P> |
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| 101 | The default optimisation level is <KBD>-O2</KBD>.<BR> |
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| 102 | Since version 5.0 of the compiler, native-STL is supported and ISO/ANSI |
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| 103 | compliance is required. |
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| 104 | |
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| 105 | <HR> |
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| 106 | <A name="10.1.4"> |
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| 107 | <H2>10.1.4 Unix/Linux - g++</H2></A> |
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| 108 | <P> |
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| 109 | OS: Linux<BR> |
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| 110 | Compiler: GNU/gcc<BR> |
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| 111 | <P> |
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| 112 | Strict ISO/ANSI compilation is forced (<tt>-ansi -pedantic</tt> compiler flags), also |
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| 113 | code is compiled with high verbosity diagnostics (<tt>-Wall</tt> flag). |
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| 114 | The default optimisation level is <KBD>-O2</KBD>.<BR> |
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| 115 | NOTE:<BR> |
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| 116 | Additional compilation options (<TT>-march=pentium4 -mfpmath=sse</TT>) to adopt |
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| 117 | Pentium4 chip specific floating-point operations on the SSE unit, can be activated |
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| 118 | by uncommenting the relevant part in the <TT>Linux-g++.gmk</TT> configuration script. |
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| 119 | By doing so, it has been verified a greater stability of results, making possible |
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| 120 | reproducibility of exact outputs between debug, non-optimised and optimised runs. |
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| 121 | A little performance improvement (in the order of 2%) can also be achieved in some |
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| 122 | cases. To be considered that binaries built using these chip-specific options will |
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| 123 | NOT be portable cross platforms; generated applications will only run on Pentium4-based |
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| 124 | architectures. |
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| 125 | |
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| 126 | <HR> |
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| 127 | <A name="10.1.5"> |
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| 128 | <H2>10.1.5 Windows - MS Visual C++</H2></A> |
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| 129 | OS: MS/Windows<BR> |
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| 130 | Compiler: MS-VC++<BR> |
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| 131 | <P> |
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| 132 | Since version .NET 7.0 of the compiler, ISO/ANSI compliance is required.<BR> |
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| 133 | See <A HREF="../../../InstallationGuide/html/PCMachines/pcMachines.html#3.1">section 3.1</A> |
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| 134 | of the Installation Guide for more detailed information.<BR> |
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| 135 | See also <A HREF="buildFile.html">section 10.6</A> for more tips. |
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| 136 | |
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| 137 | <HR> |
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| 138 | <A name="10.1.6"> |
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| 139 | <H2>10.1.6 MacOS-X - g++</H2></A> |
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| 140 | OS: MacOS/Darwin<BR> |
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| 141 | Compiler: GNU/gcc<BR> |
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| 142 | <P> |
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| 143 | The setup adopted for the <TT>g++</TT> compiler on MacOS resembles in |
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| 144 | great part the one for Linux systems.<BR> |
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| 145 | The default optimisation level in this case is <KBD>-O2</KBD>.<BR> |
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| 146 | Dynamic libraries (<TT>.dylib</TT>) are supported as well; once built, in |
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| 147 | order to run the generated application, the user must specify the absolute |
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| 148 | path in the system where they're installed with the <TT>DYLD_LIBRARY_PATH</TT> |
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| 149 | system variable. |
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| 150 | |
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| 151 | <HR> |
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| 152 | <A HREF="../../../../Authors/html/subjectsToAuthors.html"> |
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| 153 | <I>About the authors</I></A> |
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| 154 | |
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| 155 | </BODY> |
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| 156 | </HTML> |
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