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timer command

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Syntax

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timer 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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+off = do not collect and print timing information
+loop = collect only the total time for the simulation loop
+normal = collect timer information broken down in sections (default)
+full = like normal but also include CPU and thread utilzation
+sync = explicitly synchronize MPI tasks between sections
+nosync = do not synchronize MPI tasks when collecting timer info (default)
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Examples

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timer full sync
+timer loop
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Description

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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 spent in different sections of the code and thus can provide +valuable information for determining performance and load imbalance +problems. This can be done at different levels of detail and +accuracy. For more information about the timing output, please have a +look at the discussion of screen output.

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The off setting will turn all time measurements off. The loop +setting will only measure the total time of run loop and not collect +any detailed per section information. With the normal setting, +timing information for individual sections of the code are collected +and also information about load imbalances inside those sections +presented. The full setting adds information about CPU utilization +and thread utilization, when multi-threading is enabled.

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With the sync setting, all MPI tasks are synchronized at each timer +call and thus allowing to study load imbalance more accuractly, but +this usually has some performance impact. Using the nosync setting +this can be turned off (which is the default).

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Multiple keywords can be provided and for keywords that are mutually +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 +detailed and accurate timing information, but also can have a +significant negative performance impact due to the overhead of the +many required system calls. It is thus recommended to use these +settings only when making tests to identify the performance. For +calculations with few atoms or a very large number of performance, +even using the normal setting can have a measurable performance +impact. In those cases just use the loop or off setting.

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Restrictions

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none
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Default

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timer normal nosync

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