S3P command syntax

Block-by-block description of the .s3p input file. Worked cases are in the S3P module guide.

Top-level blocks: ModelInfo, FiniteElement, FrequencyScan (or WaveguideFrequency), Port, Loading, LinearSolver, PostProcess.

ModelInfo

Identical in form to Omega3P's, including Material with EpsilonImag and MuImag, PML, and SurfaceMaterial. Boundary types available: Electric, Magnetic, Exterior, Impedance, Absorbing, Waveguide. Periodic boundaries are not available in S3P.

Two extensions to SurfaceMaterial matter in S3P:

SurfaceMaterial : {
  ReferenceNumber: 3
  Sigma:     5.8e7
  Frequency: 5e9                 // frequency at which Sigma applies
  Coating : {
    Type:      ThinLossyDielectric
    Epsilon:   56
    Sigma:     12
    Thickness: 1.e-3
  }
}

Frequency fixes the frequency at which the surface impedance is evaluated for an Impedance boundary. Coating adds a thin lossy dielectric layer on the conductor without meshing it; see the T3P surface impedance tutorial for the physics.

FiniteElement

As in Omega3P: Order 1 to 6 and CurvedSurfaces.

FrequencyScan

FrequencyScan : {
  Start:    9.424e+9
  End:      14.424e+9
  Interval: 0.2e+9
}

Frequencies in Hz. If Interval exceeds End − Start, only Start is computed. For a single frequency the shorthand WaveguideFrequency: 1.3e+9 at top level is equivalent.

Port

Port : {
  ReferenceNumber: 7
  NumberOfModes:   2
}

One per Waveguide surface; absent, one mode is loaded. Load every mode that propagates anywhere in the scan range.

Loading

Dipole excitation as an alternative to port excitation, for mode identification:

Loading : {
  Type:       DipoleLoading
  Coordinate: 0., 2., 0.         // m
  Direction:  0.0, 1.0, 0.0
  Tolerance:  0.001
  Power:      1.                 // dipole moment, A·m
  Frequency:  30.e3              // Hz
}

Tolerance sets how closely the dipole direction must align with the nearest element edge.

LinearSolver

The default is the MUMPS direct solver. For large problems use an iterative solver with the multilevel preconditioner, which requires Order: 2:

LinearSolver : {
  Solver:         GMRES          // MUMPS, GMRES, CG, QMR
  Preconditioner: MP
  MaxIterations:  5000
  Tolerance:      1e-10
  PrintFrequency: 50
  QuietMode:      0              // 1 suppresses iteration output
}

MP first solves at order 1 with MUMPS to build a preconditioner, then iterates at order 2. The 2025 release notes give a resource table for this configuration on Perlmutter: 7 million elements on 4 nodes in 10 minutes, 47 million on 32 nodes in 2 hours.

PETSc solvers are also available with the same Solver: PETSc and PETScOption syntax as in Omega3P. Use -ksp_type cg only for lossless problems and -ksp_type gmres for lossy ones; complex problems need the bin-petsc-complex binaries.

PostProcess

PostProcess : {
  Toggle:     on
  PortNumber: 7                  // save fields only for this excitation port
  ModeFile:   rec                // default s3p
  WriteLoss:  on
}

Without PortNumber, fields are written for every port excitation at every frequency, which multiplies the output. WriteLoss is read by the shared post-processor in emfem/src/NewPP.C and writes .loss surface power density files.

Output files

See the S3P module guide for Reflection.out, 2dports.log, and the per-mode port files. acdtool's rf post-processor reads S3P results with FreqScanID selecting the scan point; see the acdtool command syntax.