Postprocessing And Visualization¶

Frontend postprocessing covers loading binary solution files, plotting or exporting visualization fields, writing ParaView files during backend execution, and replaying postprocessing from saved solution data.

For the standalone backend implementation details, see Postprocessing.

Output Types¶

Output	Controlled by	Notes
Saved solution binaries	`saveSolFreq`, `saveSolOpt`, `dataoutpath`	Used by `fetchsolution`, restart, and postprocess mode.
Residual histories	`saveResNorm`	Written under `dataout` or case output directories.
ParaView VTK files	`saveParaview`, `nsca`, `nvec`, `nten`, visualization callbacks	Written by the backend during solve or postprocess mode.
Frontend visualization	`vis(...)`, `visscalars`, `visvectors`, `viselem`, `visfilename`	Language helper for visualization output.
QoI outputs	`nvqoi`, `nbqoi`, `qoivolume`, `qoiboundary`	Derived quantities from model callbacks.

Enable Backend ParaView Output¶

pde.saveParaview = 1;
pde.nsca = 1;    % one scalar visualization field
pde.nvec = 1;    % one vector visualization field
pde.nten = 0;

The PDE model must define matching visscalars, visvectors, or vistensors callbacks. If these counts are zero, no corresponding visualization field is written.

Frontend Visualization Helper¶

The vis(...) helper converts returned solution fields to visualization output using frontend mesh and application metadata.

MATLABPythonJulia

visfields = sol(:, :, :, end);
vis(visfields, pde, mesh);

from exasim import vis
vis(sol, pde, mesh)

Exasim.vis(sol, pde, mesh)

Postprocess Execution Mode¶

Use pde.executionmode = 1 to run the generated executable in postprocess mode from a frontend.

pde.executionmode = 1;
runstr = runcode(pde, 1);

This requires existing compatible datain and saved solution files. It is useful when changing postprocessing options without rerunning the full solve.

Parameter-Sweep Outputs¶

Parameter sweeps write outputs into case directories:

dataout/
  physicsparam_sweep_manifest.txt
  paramcase_0001/
    physicsparam.txt
    out_np0.bin
  paramcase_0002/
    physicsparam.txt
    out_np0.bin

Postprocess each case by pointing pde.dataoutpath at the case directory or by using the standalone sweep postprocessing workflow described in Parameter sweeps.

Visualization In ParaView¶

Open the generated .pvd, .pvtu, or .vtu files from dataout. For MPI runs, open the parallel file (.pvtu or .pvd) rather than individual rank pieces when available.

Example:

paraview dataout/vis.pvd

MATLAB Analysis¶

MATLAB examples often call utilities such as fetchsolution, fetchresidual, vis, and problem-specific plotting scripts. These helpers use master and dmd to interpret per-rank backend output.

U = fetchsolution(pde, master, dmd, pde.dataoutpath);