Fortran Equation Parser

Copyright 2020 Fluid Numerics LLC

feq-parse is an equation parser Fortran class that is used to interpret and evaluate functions provided as strings.

Learn how to contribute to this repository

Installation

feq-parse can be installed using either CMake, Fortran Package Manager (fpm), or with Spack.

Prerequisites

All you need is a Fortran compiler that is compliant with the Fortran 2008 standard and supports C interoperability. You can see which compilers are regularly tested on the Github actions page. Additionally, the table below lists the supported compilers

If you are installing with CMake, you will need to have CMake version 3.0.2 or greated

CMake

For a quick installation to /usr/local/feqparse,

cd build/
cmake ../
make
sudo make install

If you'd like to run the provided tests to verify your installation,

1. Navigate to the test/ directory underneath the build/ directory.

cd test/

2. Use ctest to run the provided tests

ctest .

The above steps install

/opt/feqparse/lib/libfeqparse-static.a
/opt/feqparse/lib/libfeqparse.so
/opt/feqparse/include/FEQParse.mod

Fortran Package Manager

A Fortran Package Manager manifest file is also included, so that the library and test cases can be compiled with FPM. For example:

fpm build --profile release
fpm test --profile release

You can also run the examples included in the example/ subdirectory :

fpm run --example="*"

To use feq-parse within your fpm project, add the following to your fpm.toml file:

[dependencies]
feq-parse = { git="https://github.com/FluidNumerics/feq-parse.git" }

Or, to use a specific version:

[dependencies]
feq-parse = { git="https://github.com/FluidNumerics/feq-parse.git", tag = "v1.1.0" }

Spack

The maintainers of this repository also keep the feq-parse spack package up to date with the latest releases. This means you can easily install feq-parse from source with the spack package manager.

To get started with Spack, if you haven't already

git clone https://github.com/spack/spack ~/spack
source ~/spack/share/spack/setup-env.sh
spack compiler find

To install the latest version of feq-parse with spack,

spack install feq-parse

To install a specific version of feq-parse with spack, e.g.

spack install [email protected]

Refer to the spack documentation for further guidance on using Spack.

Supported Compilers

The following combinations are tested on the main branch of feq-parse:

Name	Version	Platform	Build System	Architecture
GNU Fortran	9, 10, 11, 12	Ubuntu 22.04.2 LTS	fpm, cmake	x86_64
GNU Fortran	13.2.0	Windows Server 2022 (10.0.20348 Build 1547) (MSYS2)	fpm, cmake	x86_64
Intel oneAPI (ifx)	2023.2	Ubuntu 22.04.2 LTS	fpm, cmake	x86_64
Intel oneAPI classic (ifort)	2021.1	Ubuntu 22.04.2 LTS	fpm, cmake	x86_64

Warning

The main branch has an experimental feature for custom functions. On Linux platforms, this is currently not functioning for ifx and ifort compilers.

Usage

Run examples with fpm

Note

Examples are now included in the example/ subdirectory

Included examples

• scalar_with_scalar_eval.f90 - Creates an equation parser, and evaluates an equation with scalar input and scalar output.
• array_with_array_eval.f90 - Creates an equation parser, and evaluates an equation with rank 1 array input and rank 1 output.
• array_with_scalar_eval.f90 - Creates an equation parser, and evaluates an equation with scalar array input and scalar output within a do loop to fill an array of values. This example is to demonstrate the performance difference with using the array evaluation.
• gaussian_scalar_multivar.f90 - Creates an equation parser, and evaluates an equation with scalar input and scalar output but with multiple independent variables (much like the example shown below).
• scalar_function_product.f90 - Creates an equation parser, and evaluates an equation with scalar array input and scalar output, and demonstrates multiplication of two functions.

To run the included examples with the fortran package manager,

fpm run --example "*"

Simple example with Makefile

Example Makefile

FC = gfortran
FLIBS += -L/opt/feqparse/lib -lfeqparse
FFLAGS += -I/opt/feqparse/include

demo : FEqParseDemo.f90
	${FC} -c FEqParseDemo.f90 ${FFLAGS}
	${FC} FEqParseDemo.o ${FFLAGS} ${FLIBS} -o $@

Example program

PROGRAM FEqParseDemo

USE FEQParse

IMPLICIT NONE

  TYPE(EquationParser) :: f
  CHARACTER(LEN=1), DIMENSION(1:3) :: independentVars
  CHARACTER(LEN=30) :: eqChar
  REAL :: x(1:3)

    ! Specify the independent variables
    independentVars = (/ 'x', 'y', 'z' /)

    ! Specify an equation string that we want to evaluate
    eqChar = 'f = exp( -(x^2 + y^2 + z^2) )'

    ! Create the EquationParser object
    f = EquationParser(eqChar, independentVars)

    ! Evaluate the equation
    x = (/ 0.0, 0.0, 0.0 /)
    PRINT*, f % evaluate( x )

END PROGRAM FEqParseDemo

Contributors

• (Maintainer) Joe Schoonover, Fluid Numerics LLC