IBM Release 1.93 manual Beta Release Limitations

Page 89

d. Adjustments to the postprocessor: (i) Figure out how to eliminate the spurious negative dissipations at the edges of material blocks; (ii) Optionally produce bitmaps and mode files unfolded along the symmetry planes. This will make the bitmaps easier to read and will make modefile sources more flexible.

e. Allow modefile sources to have a different cell size than the current simulation. We’re summing over several-block regions anyway, so there’s no reason we can’t interpolate as well.

f. Transient simulations and frequency responses via FFT methods on the transient.

g. Change to a response surface optimizer, where the values are fitted to some surface (e.g. a spline) and the surface minimum is found at each step. This can probably be done as a relatively simple mod of Nelder-Mead.

h. Generate incident-field information so that we can figure out the scattered field alone. Either a one-turn TEMPEST simulation with high accuracy enabled, or some analytical solution that ignores the boundaries. (Or maybe both--both are useful.)

i. Further improvement of the memory utilization behaviour of the postprocessor. Although the postprocessor tries to avoid holding everything in memory at once, big simulations with complicated output files (e.g. Vis5D files with >7 variables) may cause 32-bit machines to run out of virtual address space. This occurs when the total size of all the arrays gets too large (between 2 and 4 GB depending on the operating system and compiler).

j. (Fairly far out) Addition of a beam-propagation method (BPM) code to allow POEMS to simulate and optimize larger structures. This won’t happen unless there’s significant user interest.

B.4.2. Beta Release Limitations

The POEMS beta release has the following known limitations:

a. Parameter stepping isn’t yet implemented.

b. Generalized cylinders and bends aren’t yet implemented, so you’ll have to make do with fans, blocks, and grating lines of rectangular cross-section for now. It’s easy to synthesize simple curves using the FAN statement if desired.

c. Illumination beams of arbitrary pupil functions aren’t implemented yet.

d. The current optimizer is an unconstrained Nelder-Mead downhill simplex method. This needs to be replaced with a modern response surface optimizer that allows limits. Right now, the LIMIT keyword isn’t implemented, so in some cases the optimizer will just step off a cliff (e.g. specifying a line with a negative width) and crash. Since you can specify whatever merit function you like, in simple cases like this you can fold the domain, e.g. by squaring or taking the absolute value of the parameter before using it to

85

Image 89
Contents IBM T. J. Watson Research Center Yorktown Heights, NY Page IBM T. J. Watson Research Center Yorktown Heights, NY HOW Poems Works Using PoemsMotivation Chapter IntroductionPhilosophy Optimization StructurePage Poems system organization Script Operation Program OrganizationFront-End Script poems.cmd Postprocessor Empost Fdtd Engine FIDO/TEMPESTCluster Control Visualization System VIS5DParallel Processing Global Group Command ReferencePoems Command-Line Options Lambda FreqFunction HostsMacdef Which means that the host’s predefined hostname is not usedPrint MacroSimulator RandomseedSET Title World GroupVerbose BoundaryBasicstep Material GroupXrange Yrange DefineParameters epsReal epsImag muReal muImag FAN Object GroupBlock Tiledplane GratingHollowbox Cylinder Curve3DCURVE Source Group Output Group Command GroupField Postprocess GroupCAD WebpageIntegral FarfieldFlux Modematch ListMOVIE3D MovieSlice DissipationGuess Optimize GroupVariables Penalty Merit LimitStore Range Schedule GroupParameters Symmetry Computational DomainObjects Materials Perfectly-Matched LayersPlane Waves Page Beam Sources Merit Functions OptimizationPhase uniformity across a plane 10 Optimized V antenna refractive Worked Example Optimizing a V AntennaPage Predefined Constants Worked Example Doped Silica Waveguide ModeWorked Example Glass Ridge Waveguide to Free Space Coupler Confine Reserved NamesArithmetic Operators Predefined Mathematical FunctionsABS Logical OperatorsAcos AcoshCeil ATAN2COS Elintk20. LN IntegralMAX MINROOT1D RandomRound SignFlattop Analytical Pupil FunctionsMaterial Parameter Functions Time step Tempest and General Fdtd InformationStartup and Steady State Page Appendix A. V-Antenna Optimization Run Poems Input DIPOLE2I.PAR END Material END Object END World Subdomain ALLEND Output END CommandEND Source END Optimize END Postprocess Amplex PhaseexPage Page Page END Tempest Input File DIPOLE2I.PAR.IN Written by Phil Hobbs Pages of pointsource statements omitted ALL Postprocessor orders DIPOLE2I.ORDERSDIPOLE2IEXI DIPOLE2IEXQDIPOLE2IEYQ DIPOLE2IEYIDIPOLE2IEZI DIPOLE2IEZQPOSTPROC.1.NAME MiddlefluxArray Amplex POSTPROC.1.PARMSTRINGArray DIPOLE2IPHASEEXPOSTPROC.2.PARMSTRING FF2POSTPROC.6.NAME DIPOLE2IPXArray Poyntingz DIPOLE2IPZPOSTPROC.10.PARMSTRING POSTPROC.9.PARMSTRINGPOSTPROC.11.NAME Slice IndexnPOSTPROC.13.COMPARISONDOMAIN Slice PoyntingzDIPOLE2IPZXY0.BMP POSTPROC.14.NAMEDIPOLE2IPXZX0.BMP POSTPROC.16.COMPARISONDOMAINPOSTPROC.17.NAME Slice AmplexDIPOLE2IPHASEEXZX0.BMP DIPOLE2IPHASEEXXY0.BMPPOSTPROC.20.COMPARISONDOMAIN DIPOLE2IDISSZX0.BMPDIPOLE2IEXQZX0.BMP POSTPROC.24.COMPARISONDOMAINRun Results DIPOLE2I.SIMPLEX Page Page Page Page Page Tempest patches Fdtd and TempestTempest limitations Advice common to all or most Fdtd programsSample X11 Configuration Window System ConfigurationWish list Running Vis5DRelease Notes Beta Release Limitations Page Page Matlab IndexEmdenormal Emunderflow Maxordersources 81 Maxpointsources