Table of Contents

1. What is it?
2. News
3. How to use it?
   1. Compile and install the package
   2. Mathematica side
4. Portability
5. How it works?
   1. meson.build
   2. ./src/meson.build
      1. ./src/myLib/meson.build
   3. ./mma/meson.build
   4. config.wls
   5. Our cpp files
      1. The libmyLib.so cpp files (our c++ library)
      2. The libmyLibMMA.so cpp files (our MMA wrapper)
6. Useful references

What is it?

The goal is to use the Meson build system to define an easy to use and portable solution for Mathematica (MMA) Wolfram LibraryLink developments. This GitHub repository is a small illustrative example.

The important files are:

+ meson.build
+ mma/
	+ algorithm1_mma.cpp
	+ config.wls
	+ meson.build
	+ myLib_mma.cpp
	+ myLib.wl
+ src/
	+ meson.build
	+ myLib/
		+ algorithm1.cpp
		+ algorithm1.hpp
		+ meson.build

News

• <Tue Mar 26 2019> added support for MMA v10 (before only v11 was supported)

How to use it?

Compile and install the package

git clone git@github.com:vincent-picaud/mma_meson_demo.git
cd mma_meson_demo
meson build --prefix=$(pwd)/install_dir
cd build
ninja install

you will get something like:

picaud@hostname:~/GitHub/mma_meson_demo$ meson build --prefix=$(pwd)/install_dir
The Meson build system
Version: 0.49.2
Source dir: /home/picaud/GitHub/mma_meson_demo
Build dir: /home/picaud/GitHub/mma_meson_demo/build
Build type: native build
Project name: Meson_MMA_Demo
Project version: undefined
Native C++ compiler: ccache c++ (gcc 8.3.0 "c++ (Debian 8.3.0-2) 8.3.0")
Build machine cpu family: x86_64
Build machine cpu: x86_64
Program wolframscript found: YES (/usr/bin/wolframscript)
Message: MMA library installation directory: /home/picaud/.Mathematica/SystemFiles/LibraryResources/Linux-x86-64
Message: MMA package installation directory: /home/picaud/.Mathematica/Applications
Build targets in project: 2
Found ninja-1.8.2 at /usr/bin/ninja
picaud@hostname:~/GitHub/mma_meson_demo$ cd build/
picaud@hostname:~/GitHub/mma_meson_demo/build$ ninja install
[5/6] Installing files.
Installing src/myLib/libmyLib.so to /home/picaud/GitHub/mma_meson_demo/install_dir/lib/x86_64-linux-gnu
Installing mma/libmyLibMMA.so to /home/picaud/.Mathematica/SystemFiles/LibraryResources/Linux-x86-64
Installing /home/picaud/GitHub/mma_meson_demo/src/myLib/algorithm1.hpp to /home/picaud/GitHub/mma_meson_demo/install_dir/include/myLib
Installing /home/picaud/GitHub/mma_meson_demo/mma/myLib.wl to /home/picaud/.Mathematica/Applications

Remark: [role of –prefix]

This demo will generate two dynamic libraries:

• libmyLib.so a regular C++ library (totally independent of MMA)
• libmylibMMA.so a dynamic library that uses MMA's LibraryLink to wrap functions contained in libmyLib.so.

The libmyLib.so install directory is defined by the --prefix flag, with --prefix=$(pwd)/install_dir this is

/home/picaud/GitHub/mma_meson_demo/install_dir/lib/x86_64-linux-gnu

in my case.

By default libmylibMMA.so is installed in the user directory

$HOME/.Mathematica/SystemFiles/LibraryResources/Linux-x86-64

in my case.

The important point to understand is that libmylibMMA.so needs to know where the libmyLib.so library is installed. We provide this information by embedding it into the libmylibMMA.so rpath section. This section is filled by Meson at installation time. By consequence to make it works we must define this installation path.

If the --prefix variable is not defined everything works equally well except that you will need extra permissions to do a default system install (invoked when you type ninja install).

Mathematica side

To test it works, type the following under Mathematica:

<< myLib`

?"myLib`*"
data = {2, 1, 3, 5, 6, 6, 4, 3 };
algorithm1[100.,data]

it should print:

algorithm1[α_Real,vector_?VectorQ] returns α.vector

{200., 100., 300., 500., 600., 600., 400., 300.}

Remark: [ myLib`Private`unload[] ]

If you recompile the libmylib.so or libmylibMMA.so C++ library you must call myLib`Private`unload[] to make MMA aware of this modification (no need to kill the Kernel!).

Obviously, for regular uses of the MMA myLib package, you do not need this function.

Portability

I have no access to Windows. It would we nice to have some feedback concerning this platform:

• Mathematica + Linux
• Mathematica + MacOS
• Mathematica + Windows ???

How it works?

meson.build

#----------------
# Regular Meson C++ project
#----------------
project('Meson_MMA_Demo', 'cpp')

subdir('src')

#----------------
# MMA specific
#----------------

subdir('mma')

The src directory contains a regular C++ meson project, which is compiled in a regular way.

After that we move to the mma directory which is dedicated to the Mathematica part.

Remark:

Even if you do not have Mathematica installed, the C++ library (in the ./src/ directory) is properly compiled and installed.

./src/meson.build

As explained, this is a regular C++ Meson project:

myLib_inc = include_directories('.')

subdir('myLib')

./src/myLib/meson.build

For this small demo we create a dynamic library libmyLib.so containing only one file algorithm1.cpp. You can obviously add others files by appending them to the myLib_headers and myLib_sources Meson variables.

myLib_headers = ['algorithm1.hpp']
myLib_sources = ['algorithm1.cpp']

myLib_lib = library('myLib',
		   include_directories : myLib_inc,
		   install : true,
		   sources: [myLib_headers,myLib_sources])

myLib_dep = declare_dependency(include_directories : myLib_inc,
			      link_with : myLib_lib)

install_headers(myLib_headers,
		subdir : 'myLib')

./mma/meson.build

This part is specific to MMA.

#----------------
# Extract MMA information 
#----------------

# try MMA v10 first
mma_wolframscript = find_program('MathematicaScript', required: false)
if mma_wolframscript.found()
  maa_config = run_command(mma_wolframscript,'-script',files('config.wls'), check: true)
else
  # then MMA v11
  mma_wolframscript = find_program('wolframscript', required: false)
  if mma_wolframscript.found()
    maa_config = run_command(mma_wolframscript,'-f',files('config.wls'), check: true)
  else
    # no MMA? 
    warning('Mathematica not found!')
    subdir_done()
  endif
endif
    
maa_config = maa_config.stdout().split(';')

mma_include_directories = include_directories(maa_config.get(0).split(','))
mma_library_install_dir = maa_config.get(1).strip() # caveat: strip is mandatory to get 
mma_package_install_dir = maa_config.get(2).strip() # a correct filename

message('MMA library installation directory: '+mma_library_install_dir)
message('MMA package installation directory: '+mma_package_install_dir)

#----------------
# myLibMMA library 
#----------------

myLibMMA_sources = ['myLib_mma.cpp',
		    'algorithm1_mma.cpp']

shared_library('myLibMMA',
	       sources: [myLibMMA_sources],
	       dependencies: [myLib_dep],
	       include_directories: mma_include_directories,
	       install: true,
	       # libmyLibMMA.so needs to find libmyLib.so, this can be done using rpath
	       install_rpath: join_paths(get_option('prefix'),get_option('libdir')),
	       install_dir: mma_library_install_dir)

#----------------
# MMA package
#----------------

install_data('myLib.wl', install_dir: mma_package_install_dir )

In a first step we run the config.wls script to extract from MMA the relevant information required by the Meson build process. These information are printed in a form easily readable by Meson:

wolframscript -f config.wls

/usr/local/Wolfram/Mathematica/11.2/SystemFiles/IncludeFiles/C,/usr/local/Wolfram/Mathematica/11.2/SystemFiles/Links/MathLink/DeveloperKit/Linux-x86-64/CompilerAdditions;/home/picaud/.Mathematica/SystemFiles/LibraryResources/Linux-x86-64;/home/picaud/.Mathematica/Applications

These extracted information are stored into the mma_include_directories, mma_library_install_dir and mma_package_install_dir Meson variables.

In a second step we create the libmylibMMA.so dynamic library and also define its rpath variable to allow it to find the installed libmyLib.so library (see Compile and install the package).

In a third step we define where the MMA package myLib.wl will be installed (here in the mma_package_install_dir default location).

That's it!

config.wls

The config.wls script extracts the relevant information required by the Meson build process.

libraryLinkIncludeDirectories={FileNameJoin[{$InstallationDirectory,"SystemFiles","IncludeFiles","C"}],
			       FileNameJoin[{$InstallationDirectory,"SystemFiles","Links","MathLink","DeveloperKit",$SystemID,"CompilerAdditions"}]};
libraryInstallDirectory=FileNameJoin[{$UserBaseDirectory,"SystemFiles","LibraryResources",$SystemID}];
packageInstallDirectory=FileNameJoin[{$UserBaseDirectory,"Applications"}];

(* MMA < v10.1 does not have native StringRiffle *)
stringRiffle[stringList_List,sep_String]:=TextString[stringList, ListFormat -> {"", sep, ""}];
format[s_List]:=stringRiffle[s,","]

(* stdout result in a format Meson can read *)
Print[format[libraryLinkIncludeDirectories]<>";"<>libraryInstallDirectory<>";"<>packageInstallDirectory]

Our cpp files

This is really for demo purpose as we simply compute a scalar-vector product w=α.v

The libmyLib.so cpp files (our c++ library)

The ./src/myLib/algorithm1.hpp file:

#pragma once

#include <cstddef>

namespace myLib
{
  // For demo purpose: dest <- alpha.source
  void algorithm1(const double alpha,const double* source, double* dest, const size_t n);
}

The ./src/myLib/algorithm1.cpp file:

#include "myLib/algorithm1.hpp"

namespace myLib
{
  void algorithm1(const double alpha, const double* source, double* dest, const size_t n)
  {
    for (size_t i = 0; i < n; i++)
    {
      dest[i] = alpha*source[i];
    }
  }

}  // namespace myLib

The libmyLibMMA.so cpp files (our MMA wrapper)

The ./mma/myLib_mma.cpp file:

#include "WolframLibrary.h"
#include "WolframSparseLibrary.h"

extern "C" DLLEXPORT mint WolframLibrary_getVersion() { return WolframLibraryVersion; }
extern "C" DLLEXPORT int WolframLibrary_initialize(WolframLibraryData libData) { return LIBRARY_NO_ERROR; }
extern "C" DLLEXPORT void WolframLibrary_uninitialize(WolframLibraryData libData) { return; }

The ./mma/algorithm1_mma.cpp file:

#include <cassert>
#include <iostream>

#include "WolframLibrary.h"
#include "WolframSparseLibrary.h"

#include "myLib/algorithm1.hpp"

//----------------

// TODO replace asserts by MMA error message
extern "C" DLLEXPORT int algorithm1(WolframLibraryData libData, mint Argc, MArgument* Args, MArgument Res)
{
  // alpha
  const double alpha = MArgument_getReal(Args[0]);
  // source vector
  const MTensor src_tensor = MArgument_getMTensor(Args[1]);
  assert(libData->MTensor_getType(src_tensor)==MType_Real);
  const mint src_rank = libData->MTensor_getRank(src_tensor);
  assert(src_rank == 1);
  const mint* const src_dims = libData->MTensor_getDimensions(src_tensor);
  const double* const src_data = libData->MTensor_getRealData(src_tensor);
  // dest vector
  MTensor dest_tensor;
  const mint dest_rank = src_rank;
  const mint dest_dims[] = { src_dims[0] };
  libData->MTensor_new(MType_Real, dest_rank, dest_dims, &dest_tensor);
  double* const dest_data = libData->MTensor_getRealData(dest_tensor);

  // call our libmyLib.so function 
  myLib::algorithm1(alpha,src_data,dest_data,src_dims[0]);
  
  MArgument_setMTensor(Res, dest_tensor);
  return LIBRARY_NO_ERROR;
}

Useful references

• Doing nothing with LibraryLink certainly the place to begin with if you do not know LibraryLink yet.
• a short but instructive video about LibraryLink some tips (youtube video)
• Wolfram LibraryLink User Guide (official)
• https://github.com/arnoudbuzing/wolfram-librarylink-examples
• NumericArray—Compact Representation of "Numeric" Arrays (youtube video)

Note: I also have written a bash-script to generate pure C++ project templates (configured with gtest and doxygen): meson_starter_script.