Alpsize-02 Fortran Introduction

This chapter explains how to install and use ALPS Fortran. It assumes the reader has basic knowledge of Fortran programming.

Operating Environment

ALPS Fortran is a wrapper library for running Fortran code on the ALPS system. The following are required:

Installation

ALPS Fortran is provided as a patch file applied to the ALPS source tree.

1. Download the patch

   Download the ALPS Fortran archive from the ALPS repository and extract it:

    $ cd ~/
    $ wget http://xxx.xxx/alps_fortran.tar.gz
    $ tar -zxvf alps_fortran.tar.gz
   

   This creates the following files and directories:

    alps_fortran/
        + alps_fortran.patch
        + samples/
            + hello/
            + ising/
            + looper-2/
            + tutorial/
   

2. Apply the patch

   Change to the ALPS source directory (${ALPS_SRC}) and apply the patch:

    $ cd ${ALPS_SRC}
    $ patch -p0 < ~/alps_fortran/alps_fortran.patch
   

3. Build and install ALPS

   Build ALPS according to the installation documentation. ALPS Fortran is installed alongside ALPS and produces the following files (where ${ALPS_ROOT} is your ALPS installation prefix):

   • ${ALPS_ROOT}/lib/libalps_fortran.a
   • ${ALPS_ROOT}/include/alps/fortran/alps_fortran.h
   • ${ALPS_ROOT}/include/alps/fortran/fortran_wrapper.h
   • ${ALPS_ROOT}/include/alps/fortran/fwrapper_impl.h

Sample Source Code

ALPS Fortran includes three sample applications:

• “hello” — Performs no calculation; simply prints the contents of the parameter file to standard output.
• “ising” — A sample application for Ising model calculations.
• “looper-2” — A sample application demonstrating the use of an external library.

The following sections explain how to build and run the hello application. The ising and looper-2 applications follow the same procedure.

“hello” Application

The hello application consists of the following files:

• hello_impl.f90 — main program
• hello.C — sets the entry point
• hello_params — parameter file
• CMakeLists.txt — build configuration

Compiling

1. Create a build directory

    $ mkdir -p ${HOME}/alps_fortran_build/hello
    $ cd ${HOME}/alps_fortran_build/hello
   

2. Run CMake

   Specify the source directory (${SAMPLES} is the samples folder extracted from the ALPS Fortran archive):

    $ cmake -DALPS_ROOT:PATH=${ALPS_ROOT} \
    >       ${SAMPLES}/hello
   

3. Build

    $ make
   

   After a successful build, the executable hello appears in the current directory.

Thread-level Parallelization

1. Go to the build directory

    $ cd ${HOME}/alps_fortran_build/hello
   

   If any result files (hello_param.out.*) are present from a previous run, delete them before proceeding.

2. Prepare the parameter file

   Generate an XML input file from the parameter file:

    $ cp ${SAMPLES}/hello/hello_params .
    $ parameter2xml hello_params
   

   See the ALPS documentation for details on the parameter2xml command.

3. Run

    $ ./hello hello_params.in.xml
   

   The parameters defined in hello_params are printed to standard output. Example output:

    ##### alps_init() #####
    parameter X     =    3.2000000000000002
    parameter Y     =            0
    parameter WORLD = world
    defined parameter Z =            1
   

   [2011-May-13 11:45:42]: dispatching a new clone[1,1] on threadgroup[3]

    ##### alps_init() #####
    parameter X     =   -3.1000000000000001
    parameter Y     =            6
    parameter WORLD = alps
    defined parameter Z =            0
   

   [2011-May-13 11:45:42]: dispatching a new clone[2,1] on threadgroup[8]

    ##### alps_init() #####
    parameter X     =   1.00000000000000002E-003
    parameter Y     =         -100
    parameter WORLD = looper
    defined parameter Z =            0
   

   [2011-May-13 11:45:43]: dispatching a new clone[3,1] on threadgroup[7] [2011-May-13 11:45:43]: clone[3,1] finished on threadgroup[7]

    ##### alps_init() #####
    parameter X     =    100.00000000000000
    parameter Y     =            2
    parameter WORLD = japan
    defined parameter Z =            0
   

   [2011-May-13 11:45:43]: dispatching a new clone[4,1] on threadgroup[1] [2011-May-13 11:45:43]: clone[4,1] finished on threadgroup[1]

    ##### alps_init() #####
    parameter X     =    3.0000000000000000
    parameter Y     =            0
    parameter WORLD = wistaria
    defined parameter Z =            0
   

MPI Parallelization

1. Go to the build directory

    $ cd ${HOME}/alps_fortran_build/hello
   

   As above, delete any existing result files (hello_param.out.*) before proceeding.

2. Prepare the parameter file

    $ cp ${SAMPLES}/hello/hello_params .
    $ parameter2xml hello_params
   

3. Run with MPI

    $ mpirun -np 4 -x OMP_NUM_THREADS=1 ./hello --mpi hello_params.in.xml
   

   The parameters defined in hello_params are printed to standard output, as in the thread-level example above.