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Update troubleshooting guide with better instructions for geometry debugging
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Paul Romano
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1 changed files with 52 additions and 44 deletions
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@ -15,13 +15,15 @@ error you are receiving is among the following options.
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Problems with Simulations
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-------------------------
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Segmentation Fault
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******************
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RuntimeError: OpenMC aborted unexpectedly.
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******************************************
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A segmentation fault occurs when the program tries to access a variable in
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memory that was outside the memory allocated for the program. The best way to
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debug a segmentation fault is to re-compile OpenMC with debug options turned
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on. Create a new build directory and type the following commands:
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This error usually indicates that OpenMC experienced a segmentation fault. A
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segmentation fault occurs when the program tries to access a variable in memory
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that was outside the memory allocated for the program. The best way to debug a
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segmentation fault is to :ref:`compile OpenMC from source <install_source>` with
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debug options turned on. Create a new build directory and type the following
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commands:
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.. code-block:: sh
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@ -34,6 +36,28 @@ failed. If after reading the debug output, you are still unsure why the program
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failed, post a message on the `OpenMC Discourse Forum
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<https://openmc.discourse.group/>`_.
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.. _troubleshoot_lost_particles:
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WARNING: After particle __ crossed surface __ it could not be located in any cell and it did not leak.
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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During a simulation, particles can become "lost" if they reach a surface and
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there is no cell defined on the other side of the surface. It is important to
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ensure that 1) proper boundary conditions have been applied to the outer
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surfaces of your model and 2) all space in your model is filled with a cell,
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even regions that are void and have no material assigned to them.
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Please see the instructions in :ref:`troubleshoot_geometry` on how to resolve
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issues with lost particles.
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ERROR: Maximum number of lost particles has been reached.
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*********************************************************
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See the above description regarding :ref:`lost particles
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<troubleshoot_lost_particles>`. When too many particles are lost, the simulation
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will abort altogether. Again, please see the instructions in
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:ref:`troubleshoot_geometry` on how to resolve issues with lost particles.
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ERROR: No cross_sections.xml file was specified in settings.xml or in the OPENMC_CROSS_SECTIONS environment variable.
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*********************************************************************************************************************
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@ -62,22 +86,33 @@ it is recommended that data be extracted from statepoint files in a context mana
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or that the :meth:`StatePoint.close` method is called before executing a subsequent
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OpenMC run.
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.. _troubleshoot_geometry:
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Geometry Debugging
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******************
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Overlapping Cells
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^^^^^^^^^^^^^^^^^
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To identify issues in your geometry, it is highly recommended to use the `OpenMC
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Plot Explorer <https://github.com/openmc-dev/plotter/>`_ GUI application. This
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application enables you to interactively explore a model, identify regions that
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may be missing a cell definition, and identify overlapping cells.
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For fast run times, normal simulations do not check if the geometry is
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incorrectly defined to have overlapping cells. This can lead to incorrect
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results that may or may not be obvious when there are errors in the geometry
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input file. The built-in 2D and 3D plotters will check for cell overlaps at
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the center of every pixel or voxel position they process, however this might
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not be a sufficient check to ensure correctly defined geometry. For instance,
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if an overlap is of small aspect ratio, the plotting resolution might not be
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high enough to produce any pixels in the overlapping area.
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If you are having issues with lost particles, the following procedure may be
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helpful. If OpenMC reports, for example, that a particle reaching surface 50
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could not be located, look at your geometry.xml to see which cells have a region
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definition that includes surface 50, e.g.:
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To reliably validate a geometry input, it is best to run the problem in
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.. code-block:: xml
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<cell id="10" material="5" region="-49 50 -51 52" />
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This may indicate that you need to define a cell on the other side of cell 10.
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At this point, using the OpenMC Plot Explorer to locate cell 10 may provide a
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visual clue as to whether there is a missing or overlapping cell near cell 10.
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Working with the unique integer IDs of cells may be cumbersome; if you provide
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names to your cells, these names will show up in the Plot Explorer, which will
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aid geometry debugging.
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Another method to check for overlapping cells in a geometry is to run the problem in
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geometry debugging mode with the ``-g``, ``-geometry-debug``, or
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``--geometry-debug`` command-line options. This will enable checks for
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overlapping cells at every move of each simulated particle. Depending on the
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@ -92,33 +127,6 @@ output after a geometry debug run to see how many checks were performed in each
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cell, and then adjust the number of starting particles or starting source
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distributions accordingly to achieve good coverage.
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ERROR: After particle __ crossed surface __ it could not be located in any cell and it did not leak.
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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This error can arise either if a problem is specified with no boundary
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conditions or if there is an error in the geometry itself. First check to ensure
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that all of the outer surfaces of your geometry have been given vacuum or
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reflective boundary conditions. If proper boundary conditions have been applied
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and you still receive this error, it means that a surface/cell/lattice in your
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geometry has been specified incorrectly or is missing.
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The best way to debug this error is to turn on a trace for the particle getting
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lost. After the error message, the code will display what batch, generation, and
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particle number caused the error. In your settings.xml, add a :ref:`trace`
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followed by the batch, generation, and particle number. This will give you
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detailed output every time that particle enters a cell, crosses a boundary, or
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has a collision. For example, if you received this error at cycle 5, generation
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1, particle 4032, you would enter:
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.. code-block:: xml
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<trace>5 1 4032</trace>
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For large runs it is often advantageous to run only the offending particle by
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using particle restart mode with the ``-r`` command-line option in conjunction
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with the particle restart files that are created when particles are lost with
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this error.
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Depletion
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*********
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