5.2. Building a Batch Solver

The “MFiX Batch Solver” refers to the command line version of MFiX as in MFiX 2016-1 and earlier versions, to contrast it with the “MFiX Interactive Solver”. The batch solver binary is not installed in the MFiX conda package; it needs to be compiled before being used (as in previous versions of MFiX).

Using the Batch Solver is appropriate when you do not want to use the interactive features with the GUI. You cannot pause, unpause, stop, or monitor status from the batch solver.

To build the solver without interactive support, run:

> build_mfixsolver --batch
> ls
build mfixsolver

This command will build an executable mfixsolver in the current directory.

The build directory can be deleted, and the custom mfixsolver will still run. However, leaving the build directory will greatly speed up rebuilds if you want to edit the UDFs and run build_mfixsolver again.

5.2.1. Configuration options

Arguments may be passed to build_mfixsolver to specify various options: compiler, compiler flags, SMP/DMP support, and other options. All configuration options can be displayed with:

> build_mfixsolver --help

usage: build_mfixsolver [--batch] [--dmp] [--smp] [-k] [-j]
                        [FC=<Fortran compiler>]
                        [FCFLAGS=<Fortran flags>]

The most common arguments are given in the following table.




Specify the Fortran compiler command


Specify Fortran compiler flags


Enable distributed memory support (MPI)


Enable shared memory parallel support (OpenMP)

The Fortran compiler is specified by passing the FC argument to build_mfixsolver. If the FC argument is not specified, the script will search the environment for a Fortran compiler (usually gfortran).

Table 5.1 compiler value for FC




GNU Fortran compiler (serial/smp)


Intel Fortran compiler (serial/smp)


Generic MPI Fortran wrapper (dmp/combined smp-dmp)


Generic MPI Fortran wrapper (dmp/combined smp-dmp)


Intel MPI Fortran wrapper (dmp/combined smp-dmp). Older versions commonly use the mpif90 command.

Compiler flags can be specified by passing the FCFLAGS argument to build_mfixsolver. If the FCFLAGS argument is not specified, the compiler defaults are used.

Table 5.2 Compiler Flags for gfortran and Intel Fortran

GNU Fortran

Intel Fortran




Produce debugging information

-O0, -O1, -O2, -O3,

-O0, -O1, -O2, -O3,

Optimization level (refer to the compiler documentation for details on level) The following options are commonly used:

  • -O0 for debugging

  • -O2 for production


-check all

Generates runtime checks useful for debugging



Print a full stack trace when a runtime error occurs



Generates complete debugging information

Running build_mfixsolver will display the flags specified with FCFLAGS, and other compiler flags that are always defined by the build scripts:

> build_mfixsolver --batch FCFLAGS="-Wall"
-- MFIX build settings summary:
--    Build type        = RelWithDebInfo
--    Fortran compiler  = /usr/bin/gfortran
--    Fortran flags     = -Wall -cpp -ffree-line-length-0 -fconvert=big-endian -fPIC

The build_mfixsolver script will test specified Fortran compiler with any specified flags (covered next). If the compiler is not found or if the compiler doesn’t work with the specified flags, no Makefile will be generated and an error message will be printed. When posting a question on the forum about build issues, include any error messages.

5.2.2. Make options

build_mfixsolver will pass the options -j and -k on to make. Building with -j on multicore systems will speed up the build process.

> build_mfixsolver --batch -j

5.2.3. Building

To build the MFiX batch solver, run build_mfixsolver with the --batch option.

> cd tutorials/tfm/silane_pyrolysis_2d/
> ls
SP2D.mfx  usr0.f  usr1.f  usr_mod.f  usr_rates.f
> build_mfixsolver --batch
...build output...
> ls  *
build mfixsolver SP2D.mfx  usr0.f  usr0.o usr1.f  usr1.o  usr_mod.f  usr_mod.o usr_rates.f usr_rates.o

Note the absence of a lib directory. The lib directory has the Python module for the interactive solver, and therefore is not present for a batch solver. Also, mfixsolver is a binary executable (not a wrapper script).