Available Compilers

The Palmetto offers the following compiler suites for C, C++ and Fortran applications:

  1. GNU Compiler Collection (gcc)
  2. Intel Compiler Suite
  3. PGI Compiler Suite
$ module avail gcc
$ module avail intel

Compiling "Hello World" Program


Simple hello.c file that reads

{% highlight cpp %}


int main(void){ printf("Hello, world!\n"); return 0; } {% endhighlight %}

can be compiled on Palmetto using the following commands

Compiler Module Command
Intel intel/13.0 icc hello.c -o hello.x
GCC gcc/4.8.1 gcc hello.c -o hello.x
PGI pgi/16.10 pgcc hello.c -o hello.x


The same example in C++ put in a file hello.cpp

{% highlight cpp %}


int main() { std::cout << "Hello, world!" << std::endl; return 0; } {% endhighlight %}

can be compiled on Palmetto using the following commands

Compiler Module Command
Intel intel/13.0 icpc hello.cpp -o hello.x
GCC gcc/4.8.1 g++ hello.cpp -o hello.x
PGI pgi/16.10 pgc++ hello.cpp -o hello.x


To compile a simple FORTAN program test.f90

{% highlight fortran %} program test print *,'hello from fortran' end program test {% endhighlight %}

use a command appropriate for a given compiler suite

Compiler Module Command
Intel intel/13.0 ifort test.f90 -o test.x
GCC gcc/4.8.1 gfortran test.f90 -o test.x
PGI pgi/16.10 pgfortran test.f90 -o hello.x

GCC compiler options

Switch Description
-c Compile the source file but do not link
-x language Set the specific language instead of letting the compiler decide based on the source file suffix. Useful for FORTRAN i.e. language can be replaced with f77, f77-cpp-input, f95 or f95-cpp-input
-o file Change the name of the binary file from a.out to file
-v Print version of the compiler with options used for its configuration
-fopenmp Enables OpenMP directives to create a multithreaded code
-fno-gnu-keywords Turns off GNU specific language extensions
-w Suspend add warnings
-Wall Enables all warnings
-g Enables debugging information
-p or -pg Turns on gprof profiling information
-ftree-vectorizer-verbose Enables verbose mode for GCC vectorization
-O, -O1, -O2 or -O3 Different levels of code optimization; -O3 is the most aggressive
-Ofast -Ofast enables all -O3 optimizations. It also enables optimizations that are not valid for all standard-compliant programs
-Og Turns on debugging safe optimization mode
-floop-block Perform loop blocking transformations on loops
-floop-interchange Perform loop interchange transformations on loops
-ftree-vectorize Perform loop vectorization on trees. This flag is enabled by default at -O3
-funroll-loops Unroll loops whose number of iterations can be determined at compile time or upon entry to the loop
-fprefetch-loop-arrays Generate instructions to prefetch memory to improve the performance of loops that access large arrays
-ffast-math Use faster but less accurate mathematical functions
-D Define a macro
-I<dir> Add <dir> to compilers path for included files
-l<lib> Pass a library <lib> to the linker
-L<dir> Add directory <dir> to the linker library path
-march=native This selects the CPU to generate code for at compilation time by determining the processor type of the compiling machine
-ffree-form FORTRAN : Specify the layout used by the source file
-cpp FORTRAN : Enable preprocessor for FORTRAN files
-fno-underscoring FORTRAN : Do not transform names of entities specified in the Fortran source file by appending underscores to them
-fexternal-blas FORTRAN : This option will make gfortran generate calls to BLAS functions for some matrix operations like "MATMUL"
-floop-parallelize-all Identify loops that can be parallelized
-ftree-parallelize-loops=n Parallelize loops, i.e., split their iteration space to run in n threads. This option implies -pthread

More information

Intel compiler options

Switch Description
-parallel enable the auto-parallelizer to generate multi-threaded code for loops that can be safely executed in parallel
-par-reportX (X=1,2,3) control the auto-parallelizer diagnostic level
-openmp enable the compiler to generate multi-threaded code based on the OpenMP* directives
-openmp-reportX (X=1,2,3) control the OpenMP parallelizer diagnostic level
-fast enable -xHOST -O3 -ipo -no-prec-div -static options set by -fast cannot be overridden with the exception of -xHOST, list options separately to change behavior
-O0 disable optimizations
-O1 optimize for maximum speed, but disable some optimizations which increase code size for a small speed benefit
-O2 optimize for maximum speed (DEFAULT)
-O3 optimize for maximum speed and enable more aggressive optimizations that may not improve performance on some programs
-threads specify that multi-threaded libraries should be linked against -nothreads disables multi-threaded libraries
-vec enables (DEFAULT) vectorization (-novec disables vectorization)
-mkl link to the Math Kernel Library (MKL) and bring in the associated headers, -mkl= one of parallel (default), sequential or cluster
-opt-matmul replace matrix multiplication with calls to intrinsics and threading libraries for improved performance (DEFAULT at -O3 -parallel)
-xHost generate instructions for the highest instruction set and processor available on the compilation host machine
-integer-size XX specifies the default size of integer and logical variables size: 16, 32, 64
-real-size XX specify the size of REAL and COMPLEX declarations, constants, functions, and intrinsics size: 32, 64, 128
-w disable all warnings, equivalent to -warn none or -nowarn
-warn all enables all warnings
-L<dir> instruct linker to search <dir> for libraries
-l<string> instruct the linker to link in the -l<string> library
-Wl,<o1>[,<o2>,...] pass options o1, o2, etc. to the linker for processing
-V display compiler version information
-multiple-processes[=<n>] create multiple processes that can be used to compile large numbers of source files at the same time
-c compile to object (.o) only, do not link
-S compile to assembly (.s) only, do not link
-o <file> name output executable file
-g produce symbolic debug information in object file (implies -O0 when another optimization option is not explicitly set)
-p compile and link for function profiling with UNIX gprof tool, -pg is also valid
-D<name>[=<text>] define macro
-I<dir> add directory to include file search path
-fpp run Fortran preprocessor on source files prior to compilation