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Getting Started With Frontends

This page shows the smallest useful frontend workflow and explains the files that Exasim creates. For complete example applications, start from the directories under examples/.

Prerequisites

Install Exasim with frontend support:

export EXASIM_PREFIX=/path/to/prefix
cmake -S Exasim -B Exasim-build \
  -DCMAKE_INSTALL_PREFIX=$EXASIM_PREFIX \
  -DEXASIM_FRONTENDS=ON
cmake --build Exasim-build -j
cmake --install Exasim-build

The frontend setup scripts should set or discover EXASIM_PREFIX. If you use a nonstandard installation, set it explicitly before running examples:

setenv('EXASIM_PREFIX', '/path/to/exasim-prefix')
run('/path/to/exasim-prefix/share/exasim/matlab/exasim_setup.m')

export EXASIM_PREFIX=/path/to/exasim-prefix
python3 pdeapp.py

export EXASIM_PREFIX=/path/to/exasim-prefix
julia pdeapp.jl

Minimal Simulation Skeleton

The exact PDE model functions are problem dependent, but all frontends use the same skeleton.

[pde, mesh] = initializeexasim();

pde.model = "ModelD";
pde.modelfile = "pdemodel";    % pdemodel.m on the MATLAB path
pde.nd = 2;
pde.ncu = 1;
pde.nc = 3;                    % u plus q for a 2D LDG model
pde.porder = 2;
pde.physicsparam = [1.0];
pde.saveParaview = 1;

% Fill mesh.p, mesh.t, mesh.boundaryexpr, and mesh.boundarycondition here.
[sol, pde, mesh, master, dmd, comstr, runstr] = exasim(pde, mesh);

from exasim import initializeexasim, exasim

pde, mesh = initializeexasim()
pde["model"] = "ModelD"
pde["modelfile"] = "pdemodel"   # pdemodel.py in the run directory
pde["nd"] = 2
pde["ncu"] = 1
pde["nc"] = 3
pde["porder"] = 2
pde["physicsparam"] = [1.0]
pde["saveParaview"] = 1

# Fill mesh["p"], mesh["t"], boundary expressions, and boundary conditions.
sol, pde, mesh = exasim(pde, mesh)

using Exasim

pde, mesh = Exasim.initializeexasim()
pde.model = "ModelD"
pde.modelfile = "pdemodel"      # pdemodel.jl in the run directory
pde.nd = 2
pde.ncu = 1
pde.nc = 3
pde.porder = 2
pde.physicsparam = [1.0]
pde.saveParaview = 1

# Fill mesh.p, mesh.t, boundary expressions, and boundary conditions.
sol, pde, mesh = Exasim.exasim(pde, mesh)

Generated Files

By default, the frontends use two locations:

Location Purpose
pde.datapath User-visible runtime data such as datain/ and dataout/. Defaults to the current directory.
pde.builddir / pde.buildpath Hidden generated-code and build area. Defaults to .exasim/.

Typical output layout:

<case>/
  datain/
    app.bin
    mesh.bin
    sol.bin
  dataout/
    out_np0.bin
    out_residualnorms0.bin
    vis*.vtu
  .exasim/
    model cache/build files

Parameter sweeps add case directories such as dataout/paramcase_0001/ and a sweep manifest. See Parameter sweeps.

First Existing Examples

Run a language-matched example from its directory:

cd examples/Poisson/poisson2d
matlab -batch pdeapp
python3 pdeapp.py
julia pdeapp.jl

Not every example has all three language files. The repository contains representative MATLAB, Python, and Julia examples across Poisson, advection, Euler, Navier-Stokes, MHD, and other modules.

See Also