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--- howto:compiling_tips_n_tricks [2013/07/19 09:51]
kevin
+++ howto:compiling_tips_n_tricks [2021/12/09 16:42] (current)
@@ Line 9: / Line 9: @@
 > Many people write the first and last as C/C++.  That's misleading.  C and C++ are separate languages.  Confusing them is responsible for many problems.
-The compilers found at the CHPC fall into three families: GCC, Intel and Sun Studio.
+The compilers found at the CHPC fall into three families: GCC, Intel and [[guide:m9000|Sun Studio]].
 > 'GCC' stands for GNU Compiler Collection; 'gcc' stands for GNU C Compiler; try not to confuse them 8-)
->> There's a fourth family, IBM XL, but we won't worry about it since the P690s are gone and BG/P is DOA.
+>> There's a fourth family, IBM XL, but we won't worry about it since the P690s are gone and BG/P is in hibernation.
 ====Table of Compilers and their Command Names====
@@ Line 25: / Line 25: @@
 <code bash>
-you@login01:~$ gcc -o hello hello.c
+gcc -o hello hello.c
 </code>
@@ Line 31: / Line 31: @@
 <code bash>
-you@login01:~$ ifort -o hello hello.f90
+ifort -o hello hello.f90
 </code>
@@ Line 51: / Line 51: @@
 ====Example====
-When building an MPI library --- for example, OpenMPI --- one should specify all four since MPI provides MPI compilers for:
+When building an MPI library --- for example, OpenMPI --- one should set all four variables since MPI provides MPI compilers for:
 | ''mpicc'' | MPI C compiler ^
@@ Line 58: / Line 58: @@
 | ''mpif90'' | MPI Fortran 90 compiler |
-When building OpenMPOI then, before the usual ''make; make install'' command, tell ''configure'' which compilers to use:
+When building OpenMPI then, before the usual ''make; make install'' command, tell ''configure'' which compilers to use:
-<code>
+<code bash>
 ./configure --prefix=$HOME/mpi/intel/ \
 CC=icc CXX=icpc F77=ifort FC=ifort \
@@ Line 68: / Line 68: @@
 > The above example uses Intel compilers and also builds in InfiniBand support.
+=====Which Compilers am I Using?=====
+That's a very good question.
+====Table of Compiler Commands for Version====
+| Language ^  GCC         ^  Intel     |
+^ C        | ''%%gcc --version%%''      | ''icc -v''    |
+^ Fortran  | ''%%gfortran --version%%'' | ''ifort -v''  |
+^ C++      | ''%%g++ --version%%''      | ''icpc -v''   |
+The ''-v'' options stands for 'verbose' and it produces additional messages when used with any compiler command.  For the Intel compilers, ''-v'' by itself just produces the version:
+<code bash>
+login01:~$ icc -v
+Version 12.0.0
+</code>
+For the GCC compilers, ''-v'' produces a lot more information:
+<code>
+login01:~$ gfortran -v
+Using built-in specs.
+Target: x86_64-redhat-linux
+Configured with: ../configure --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info
+--enable-shared --enable-threads=posix --enable-checking=release --with-system-zlib
+--enable-__cxa_atexit --disable-libunwind-exceptions --enable-libgcj-multifile --enable-
+languages=c,c++,objc,obj-c++,java,fortran,ada --enable-java-awt=gtk --disable-dssi
+--disable-plugin --with-java-home=/usr/lib/jvm/java-1.4.2-gcj-1.4.2.0/jre --with-cpu=generic
+--host=x86_64-redhat-linux
+Thread model: posix
+gcc version 4.1.2 20080704 (Red Hat 4.1.2-52)
+</code>
+Which is why GCC compilers provide the long option ''%%--version%%'' to just obtain the version:
+<code>
+login01:~$ gfortran --version
+GNU Fortran (GCC) 4.1.2 20080704 (Red Hat 4.1.2-52)
+Copyright (C) 2007 Free Software Foundation, Inc.
+GNU Fortran comes with NO WARRANTY, to the extent permitted by law.
+You may redistribute copies of GNU Fortran
+under the terms of the GNU General Public License.
+For more information about these matters, see the file named COPYING
+</code>
+> You also get a copyright message but the version is in the first line.
+> <code>login01:~$ gfortran --version | head -1
+GNU Fortran (GCC) 4.1.2 20080704 (Red Hat 4.1.2-52)</code>
+Using a different, newer, version of GCC is easy through the use of GNU [[guide:compiling|modules]]:
+<code bash>
+login01:~$ module load gcc
+login01:~$ gfortran --version | head -1
+GNU Fortran (GCC) 4.7.2
+</code>

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