timestep command

Syntax

timers args
  • args = one or more of off or loop or normal or full or sync or nosync
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)

Examples

timers full sync
timers loop

Description

Select to which level of detail LAMMPS is performing internal profiling.

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.

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.

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).

Multiple keywords can be provided and for keywords that are mutually exclusive, the last one in that group is taking effect.

Warning

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. It is recommended in those cases to use the loop or off setting.

Restrictions

none

Default

timers normal nosync