forked from lijiext/lammps
86 lines
2.8 KiB
Plaintext
86 lines
2.8 KiB
Plaintext
.. index:: timestep
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timestep command
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================
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Syntax
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""""""
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.. parsed-literal::
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timers args
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* *args* = one or more of *off* or *loop* or *normal* or *full* or *sync* or *nosync*
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.. parsed-literal::
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*off* = do not collect and print timing information
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*loop* = collect only the total time for the simulation loop
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*normal* = collect timer information broken down in sections (default)
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*full* = like *normal* but also include CPU and thread utilzation
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*sync* = explicitly synchronize MPI tasks between sections
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*nosync* = do not synchronize MPI tasks when collecting timer info (default)
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Examples
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""""""""
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.. parsed-literal::
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timers full sync
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timers loop
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Description
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"""""""""""
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Select to which level of detail LAMMPS is performing internal profiling.
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During regular runs LAMMPS will collect information about how much time is
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spent in different sections of the code and thus can provide valuable
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information for determining performance and load imbalance problems. This
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can be done at different levels of detail and accuracy. For more
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information about the timing output, please have a look at the :ref:`discussion of screen output <start_8>`.
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The *off* setting will turn all time measurements off. The *loop* setting
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will only measure the total time of run loop and not collect any detailed
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per section information. With the *normal* setting, timing information for
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individual sections of the code are collected and also information about
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load imbalances inside those sections presented. The *full* setting adds
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information about CPU utilization and thread utilization, when multi-threading
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is enabled.
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With the *sync* setting, all MPI tasks are synchronized at each timer call
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and thus allowing to study load imbalance more accuractly, but this usually
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has some performance impact. Using the *nosync* setting this can be turned
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off (which is the default).
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Multiple keywords can be provided and for keywords that are mutually
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exclusive, the last one in that group is taking effect.
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.. warning::
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Using the *full* and *sync* options provides the most
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detailed and accurate timing information, but also can have a significant
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negative performance impact due to the overhead of the many required system
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calls. It is thus recommended to use these settings only when making tests
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to identify the performance. For calculations with few atoms or a very
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large number of performance, even using the *normal* setting can have
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a measurable performance impact. It is recommended in those cases to use
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the *loop* or *off* setting.
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Restrictions
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""""""""""""
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none
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Related commands
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""""""""""""""""
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:doc:`run post no <run>`, :doc:`kspace_modify fftbench <kspace_modify>`
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Default
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"""""""
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timers normal nosync
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.. _lws: http://lammps.sandia.gov
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.. _ld: Manual.html
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.. _lc: Section_commands.html#comm
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