Finite-Element Spectral Transfer of Radiation Peter Hakel Los Alamos National Laboratory hakel@lanl.gov

Version 0.1 -- June 2015 Version 0.2 -- March 2016 Version 0.3 -- August 2016 Version 0.4 -- October 2016 Version 0.5 -- August 2017 Version 0.6 -- April 2018 Version 0.7 -- November 2018 Version 0.8 -- March 2019 Version 0.9 -- October 2020 CODE NAME: FESTR (C15068) Classification Review Number: LA-CC-15-045 Export Control Classification Number (ECCN): EAR99 B&R Code: DP1516090

Description:

FESTR is a modeling tool for calculating spectroscopic-quality synthetic outputs (e.g., spectra and images) based on (in general) the time evolutions of 3-D spatial distributions of materials characterized by their chemical composition, temperature, and density conditions. FESTR performs raytracing across unstructured meshes, builds intrinsic optical properties of mixed materials by performing equation-of-state lookups in external data, and then solves the radiation-transport equation along rays to obtain emergent time and space resolved synthetic spectra. These results can be further processed into time and/or space integrated spectra, as well as into spectral-band-integrated synthetic images, radiated power histories, and total radiated energy values. FESTR is also applicable to spatial reconstructions of material properties via the analysis of experimental data.

Publications:

Peter Hakel, "FESTR: Finite-Element Spectral Transfer of Radiation spectroscopic modeling and analysis code", Computer Physics Communications, vol. 207, pp. 415-425 (2016). (open access) http://dx.doi.org/10.1016/j.cpc.2016.05.027

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Version Log:

0.1, June 2015 Initial release: *) EOS and optical data lookups in pure-element databases (with ionization) and their mixing according to the chemical composition, *) 3-D raytracing across unstructured meshes (Face = Sphere, Cone, Polygon, Surface have been implemented), *) solution of the steady-state radiation-transport equation along Rays and calculation of space/time resolved/integrated spectra, *) Detectors using parallel Rays (infinite focus) coded and tested, *) non-parallel Rays (parallax effects) also coded, but not tested yet, *) tools for creating synthetic 2-D spectral-band-integrated images, *) a simple but general native unit test framework (class Test).

0.2, March 2016 Release: festr_v0.2.tgz, added: *) Doxygen documentation of the source code, accessible via file: doc/html/index.html to be viewed with a web browser, *) classes Objective, Goal in support of the analysis mode, *) class Progress for monitoring of progress of the calculation.

0.3, August 2016 Release: festr_v0.3.tgz, added: *) bug fix in Detector::patch_string, where a missing (symmetry != "none") branch was added; added two new associated unit tests in test_Detector.cpp: Detector_patch_string_symmetry_none, Detector_patch_string_symmetry_spherical; adjusted "expected" values in two existing unit tests in test_Diagnostics.cpp also affected by the above described change: Diagnostics_do_history_SphSym1d_symmetry_spherical_center_patch Diagnostics_do_history_SphSym1d_flat_backlighter_center_patch *) bug fix in Zone::load_mat, to ensure correct function in analysis mode.

0.4, October 2016 Release: festr_v0.4.tgz, added: *) bug fix in Detector::do_Ray, where the wrong use of the "patch" variable in the "spherical cap" if-test was changed to use the correct "direction" variable; *) a hard zero was replaced with 1.0e-19 in Cone::contains in order to avoid spurious rejection of a valid solution due to round-off errors for Rays exactly following the z-axis; three new unit tests (with names containing "Ray_on_axis") were added to file test_Cone.cpp to cover this edge case.

0.5, August 2017 Release: festr_v0.5.tgz: *) Diagnostics constructor was extended to copy the times.txt input file from the Hydro directory into the Output directories of all Detectors in order to support postprocessing utilities time_hist and time_intavg, unit test Diagnostics_Detector0_times_file_copy was added, *) files Sphere1d-yp_time0_img.dat, Sphere1d-yp_time0_img.png, c_car_img, car_img.cpp were added in directory img/ to enable the generation of synthetic images from generic space-resolved spectra (i.e., from spectra whose Detector has symmetry = none), *) the meaning of the third argument in functions nearest and nearest_exh (file utilities.h) has been changed in order to allow the optimization of the subsequent loop in nearest_exh, calls to these functions were updated accordingly, two new tests (utilities_nearest0 and utilities_nearest_exh_empty) were added to cover edge cases, *) function Diagnostics::do_history() was renamed execute(), refactored, and split into two shorter functions: Diagnostics::postprocess() and Diagnostics::analyze(), file do_history.cpp was renamed diag_exec.cpp, replacements of "do_history" with "execute" were carried out in the file Test/test_Diagnostics.cpp, *) code in function Diagnostics::postprocess() was refactored to accomodate MPI-parallelization of time steps using class TaskPool, *) code in function Detector::yt_to_files() was refactored to accomodate MPI-parallelization of time integration using class ReducePool, a new function Detector::yst_using_mpi() was added in a similar manner, *) OpenMP threading directives were added to ArrDblLoop.cpp and Objective.h, *) several methods in class ArrDbl were found to be thread-unsafe and corrected accordingly, *) makefile was enhanced with additional variables controlling the level of optimization (opt), OpenMP threading (omp), and MPI parallelization (mpi), *) for completeness, "np" fields were added for each Zone in the file Test/Analysis1/time_0.txt, *) NOTE: the unit tests are not designed to run with MPI parallelization.

0.6, April 2018 Release: festr_v0.6.tgz: *) The src/Sample/Data/Table.txt file content was updated to handle element symbols starting with an uppercase letter, *) Portland compiler name was changed from pgcpp to pgc++ in the makefile, *) unit test names now use hyphen (instead of the original underscore) to mark the end of the tests' group names (change in Test::get_id), *) function replace_in_string was added in utilities, new related unit tests were also added, *) function string_to_bool (in utilities) was extended to accept "yes" and "no" inputs, *) new "tracking" members were added to classes Detector and Ray to mark whether partial spectral results (along the specified Rays) should also be output (the default is "no" i.e., "false"), several unit tests were added and modified accordingly, *) new members "nzd", "iz", "distance", "froot", and "hroot" were added in class Ray to support the newly added "tracking" capability of partial spectral results along a Ray, functions Detector::do_Ray, Detector::omega_string, Ray::trace, and Ray_cross_Zone were modified to support this new capability, *) additional argument "nzmesh" was added to function Ray::cross_Zone, *) Database constructor was modified to allow the reading of photon-energy grids made of doubles (instead of the original integers), *) Detector constructor was modified to print an error message and halt the program, if the Detector's photon-energy range is entirely outside of the photon-energy range of the Database, *) Database constructor was given a third argument (type bool) to flag whether the database path was set to "tops_default/" or not, a getter function for this new member of class Database was added, all affected unit tests were updated with this value set to "false" and the festr.cpp file was changed accordingly.

0.7, November 2018 Release: festr_v0.7.tgz: *) The makefile was generalized to use wildcard functionality and placed into the new directory named "common" along with MPI and unit-test relevant source files, *) the source file containing the "main" function was renamed "festr_main.cpp" and all the other production source files were moved to the new "src" subdirectory (within the old "src"), *) the Doxygen documentation (located in directory "doc/html") now captures entities declared and defined in this new "src/src" subdirectory (i.e., "main" and "common" files are no longer included), ) object files are now assembled into library (".a") archive files before linking with the object file containing the "main" function; this change should facilitate the reuse of FESTR functions in other possible future projects, *) new "log" rule added to the makefile creates the file named "makelog.txt" containing the configuration of the latest "make libfestr.a" build; this new file therefore contains a record of the build choices made for "libfestr.a" for future reference, *) entities from "utilities" are now encapsulated in the namespace "utils"; entities from "constants" are now encapsulated in the namespace "cnst"; all source code was updated accordingly, *) the filename extensions of include files were changed from ".cpp" to ".inc", *) subdirectory "Test" was renamed "UniTest", and two new files named "tests_headers.inc" and "tests_runs.inc" were created by cutting FESTR-specific code out of "tests.cpp" (now located in the "common/UniTest" directory), *) the new file "test_Face.cpp" containing an empty function was created per the demands of the updated (and more automated) makefile, *) compilation scripts and source code for supporting programs were modified to accommodate the changes described above.

0.8, March 2019 Release of version 0.8: *) The copyright notice was changed to reflect the transition of the Los Alamos National Laboratory M&O contract from Los Alamos National Security, LLC, to Triad National Security, LLC, *) in class ArrDbl return types were changed to references for all compound assignments, const was added to return types of unary and binary operators, four unit tests covering compound assignments with self were added in file test_ArrDbl.cpp, *) file "img/img.py" was converted to Python 3 and made self-executable, *) "build" subdirectory was created to store object files during the compilation; the makefile was changed accordingly.

0.9, October 2020 Release of version 0.9: *) The code was upgraded to the C++11 standard and ported to Windows 10; the makefile was changed to support Windows compilation using MinGW, *) raw pointers inside containers were replaced with smart pointers, *) struct PatchID was added in file Detector.cpp to facilitate the redeployment of MPI parallelization using TaskPool away from time steps to parallelization over Detector patches, *) the Detector class was modified to allow its pointing to an arbitrary point with an arbitrary aperture angle; units tests for Detector and Diagnostics were added and/or modified, ) the "options" file in postprocessing mode now ends with the "tmin_tmax" pair of numbers (in seconds) defining the interval of interest from the Hydro time history; the "main" function and class Diagnostics (and some of its unit tests) were modified accordingly, new unit tests named Hydro-Hydro_subset were added in test_Hydro.cpp, *) public portions of class declarations are now listed first, *) calls to push_back() were replaced with calls to emplace_back(), *) class ArrDbl was given its own emplace_back() method, a corresponding unit test was added in test_ArrDbl.cpp, *) method Grid::add_node() was overloaded to accept an rvalue reference, *) copy constructor and assignment of class StoichZbar were defaulted, *) the creation of Face-derived objects was moved into struct FaceFactory, *) virtual methods in Face-derived classes now use the override keyword, *) a number of changes were made to increase the numerical robustness of the raytracer in case of Mesh of Cones with Rays grazing nearly parallel to near-disk Cone Faces: *) Cone::SMALL is now 5.0e-7 cm instead of the original 1.0e-8 cm, ) Cone::MINIMUM_DISTANCE = 1.0e-6 cm was added (Rays hitting a Cone within this distance of one of its Nodes are moved inward along the Cone to this distance, Vector3d::linear_Vector3d_fit() was added to facilitate the associated interpolation, Cone::get_endpoints() was added and Cone::intercept() was modified, new units tests were added: Cone-get_endpoints and some extant ones like Cone-intercept_disk0_w in test_Cone.cpp had their expected answer modified), *) Cone::ZERO = 1.0e-19 cm2 was added and Cone::contains() was modified to test individual components rather than the scalar product of two vectors as a whole), *) Vector3d::ZERO = 0.0 was added and Vector3d::is_between() was modified to test individual components rather than the scalar product of two vectors as a whole), new unit test Vector3d-linear_Vector3d_fit was added in test_Vector3d.cpp, ) in utils::solve_quadratic() the discriminant is now replaced with a hard zero, if its original absolute value was less or equal to TOL; this change makes the "cones_tiebreaks_to_top_Zone" unit tests in test_Mesh.cpp pass also with the PGI compiler (they were already passing with the GNU and Intel compilers), *) a short-hop branch was added to Cone::intercept() to facilitate Ray advancement near the Cone's vertex; unit tests with Mesh defined in file mesh_cones_vertex.inc were added to test_Mesh(), *) to further improve the numerical robustness of the raytracer, methods Face::face_point() and Zone::zone_point() were added (along with corresponding new unit tests); method Zone::hit() was extended to find a hitpoint based on Zone::zone_point() in case the original search (based on the Ray's exit point p) fails (new unit tests were also added), *) utils::get_grid() was modified to prevent a division by nm1==0, *) utils::double_to_string() was modified to remove a leading '0' in 3-digit exponents (due to formatting seen on Windows), *) Progress::print() was given an extra constant named EPS to address round-off issues in the floating-point numerics seen on Windows with optimization turned on, *) Sphere::intercept() now returns no solution, if the two roots are too close to each other; the expected values in "intercept-one" unit tests were changed accordingly, *) Cone::intercept() now returns no solution, if the Ray runs along its face, *) arbitrary backlighters can now be read in from input files, whose names are specified in the Detector's definition file as: backlighter file , *) utils::normalize() function was added along with new unit tests to renormalize a vector of doubles, *) methods Table::atom_to_mass() and Table::mass_to_atom() were added along with new unit tests to convert between atom and mass material fractions, *) function Table::get_elements() was added to return all present elements, *) the src/UniTest directory was added to the include directories in the makefile and #include's now use <> brackets around the file names, *) unit-test sources were given their own .h files and all the test sources were modified accordingly, *) check_to_disable_test() was converted from a free function to a public method of class Test; all unit-test drivers were changed accordingly, *) a branch was added in Cone::intercept to bypass numerical issues for vertical Rays; two new associated units tests were added in file test_Cone.cpp, which include the new file cone_vertical.inc, *) copy assignment of StoichZbar in Database.h was explicitly deleted, *) a new Ray-casting scheme was implemented for Ray bundles, *) Ray-casting within a Ray bundle can be threaded with OpenMP.