`pdeapp.txt` Guide¶

pdeapp.txt is the Text2Code application file. It is a flat list of semicolon-terminated key = value; statements that configure the model file, mesh file, discretization, solver, runtime backend, parameter sweeps, and output behavior.

For the exhaustive keyword table, see pdeapp.txt fields. This page explains how to use those keywords in complete applications.

Syntax Rules¶

key = value;

Common value forms:

model = "ModelD";
porder = 3;
NewtonTol = 1e-06;
physicsparam = [1.0, 0.72, 1000.0];
boundaryexpressions = ["abs(y)<1e-8", "abs(x-1)<1e-8"];
physicsparamcases = [0.5; 1.0; 2.0];

Important parser behavior:

statements end with ;;
strings are quoted;
numeric lists use brackets;
matrices can use nested rows or semicolon-separated rows;
numeric expressions in boundary expressions are evaluated by Text2Code;
write floating-point values with a decimal or exponent when the backend field is floating point, for example time = 0.0;.

Required Fields¶

The parser requires these keys:

Key	Purpose
`model`	Model class selector such as `"ModelD"`.
`modelfile`	Path to `pdemodel.txt`.
`meshfile`	Path to mesh input, commonly `grid.bin`.
`discretization`	`"ldg"` or `"hdg"`.
`platform`	`"cpu"` or `"gpu"`.
`mpiprocs`	Number of MPI ranks.
`porder`	Polynomial order.
`pgauss`	Quadrature degree/order.
`physicsparam`	Runtime physical parameter vector.
`tau`	Stabilization parameter vector.
`boundaryconditions`	Boundary-condition IDs.
`boundaryexpressions`	Geometric predicates for boundary groups.

Application Settings¶

model = "ModelD";
modelfile = "pdemodel.txt";
meshfile = "grid.bin";
discretization = "hdg";
platform = "cpu";
modelnumber = 0;
gencode = 1;
gendatain = 1;

gencode = 1 asks Text2Code to generate model C++ kernels from pdemodel.txt. gendatain = 1 asks it to write the backend input bundle.

Physics Configuration¶

ncu = 1;
ncv = 0;
ncw = 0;
physicsparam = [1.0];
externalparam = [0.0, 0.0];
tau = [1.0];

physicsparam is passed to pdemodel.txt functions as mu. externalparam is passed as eta/external data in the generated model interface. Keep the length and meaning of these vectors fixed across runs and sweeps.

Mesh Configuration¶

meshfile = "grid.bin";
boundaryconditions = [1, 1, 1, 1];
boundaryexpressions = [
  "abs(y)<1e-8",
  "abs(x-1)<1e-8",
  "abs(y-1)<1e-8",
  "abs(x)<1e-8"
];
curvedboundaries = [0, 0, 0, 0];
curvedboundaryexprs = ["", "", "", ""];

Boundary expressions classify mesh faces geometrically. Boundary-condition IDs must match the boundary logic implemented in pdemodel.txt functions such as Ubou, Fbou, and FbouHdg.

Solver Settings¶

NewtonIter = 20;
NewtonTol = 1e-06;
GMRESiter = 200;
GMRESrestart = 50;
GMREStol = 1e-08;
preconditioner = 1;
precMatrixType = 0;

These fields configure the backend nonlinear and linear solvers. Use tighter tolerances only when the physics and discretization justify the additional work.

Time Integration Settings¶

Steady-state run:

dt = [0.0];
time = 0.0;
torder = 1;
nstage = 1;

Time-dependent run:

time = 0.0;
dt = [repeat(1e-3, 100)];
saveSolFreq = 10;
torder = 2;
nstage = 2;

A positive entry in dt marks the problem as time-dependent.

Execution, MPI, And GPU Settings¶

Serial CPU:

platform = "cpu";
mpiprocs = 1;

MPI CPU:

platform = "cpu";
mpiprocs = 4;

GPU:

platform = "gpu";
mpiprocs = 1;

The installed Exasim package and CMake app determine whether CUDA or HIP is used for GPU execution.

Parameter Sweep Settings¶

physicsparam = [1.4, 0.72, 500.0];
physicsparamcases = [
  1.4, 0.72, 500.0;
  1.4, 0.72, 1000.0;
  1.4, 0.72, 1500.0
];
physicsparamwarmstart = 1;

Each row of physicsparamcases is one run. The standalone app writes outputs to deterministic directories such as dataout/paramcase_0001/ and writes physicsparam.txt metadata for reproducibility.

Postprocessing And Output Settings¶

saveParaview = 1;
nsca = 2;
nvec = 1;
nten = 0;
nvqoi = 2;
saveResNorm = 1;
saveSolFreq = 1;
saveSolOpt = 1;

Visualization counts must match generated VisScalars, VisVectors, and VisTensors outputs in pdemodel.txt. QoI counts must match QoIvolume and QoIboundary outputs.

Complete Poisson App Example¶

model = "ModelD";
modelfile = "pdemodel.txt";
meshfile = "grid.bin";
discretization = "hdg";
platform = "cpu";
mpiprocs = 1;

porder = 3;
pgauss = 6;
ncu = 1;
ncv = 0;
ncw = 0;
nsca = 2;
nvec = 1;
nvqoi = 2;

NewtonIter = 20;
NewtonTol = 1e-06;
GMRESiter = 200;
GMRESrestart = 50;
GMREStol = 1e-08;
preconditioner = 0;

time = 0.0;
dt = [0.0];
tau = [1.0];
physicsparam = [1.0];
externalparam = [0.0, 0.0];

boundaryconditions = [1, 1, 1, 1];
boundaryexpressions = ["abs(y)<1e-8", "abs(x-1)<1e-8", "abs(y-1)<1e-8", "abs(x)<1e-8"];

pdeapp.txt Guide¶