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write_restart command


write_restart file keyword value ... 


write_restart restart.equil
write_restart restart.equil.mpiio
write_restart flow.%.* nfile 10 


Write a binary restart file with the current state of the simulation.

During a long simulation, the restart command can be used to output restart files periodically. The write_restart command is useful at the end of a run or between two runs, whenever you wish to write out a single current restart file.

Similar to dump files, the restart filename can contain two wild-card characters. If a "*" appears in the filename, it is replaced with the current timestep value. If a "%" character appears in the filename, then one file is written by each processor and the "%" character is replaced with the processor ID from 0 to P-1. An additional file with the "%" replaced by "base" is also written, which contains global information. For example, the files written for filename restart.% would be restart.base, restart.0, restart.1, ... restart.P-1. This creates smaller files and can be a fast mode of output and subsequent input on parallel machines that support parallel I/O. The optional fileper and nfile keywords discussed below can alter the number of files written.

Restart files can be read by a read_restart command to restart a simulation from a particular state. Because the file is binary, it may not be readable on another machine.

IMPORTANT NOTE: Although the purpose of restart files is to enable restarting a simulation from where it left off, not all information about a simulation is stored in the file. For example, the list of fixes that were specified during the initial run is not stored, which means the new input script must specify any fixes you want to use. See the read_restart command for details about what is stored in a restart file.

The optional nfile or fileper keywords can be used in conjunction with the "%" wildcard character in the specified restart file name. As explained above, the "%" character causes the restart file to be written in pieces, one piece for each of P processors. By default P = the number of processors the simulation is running on. The nfile or fileper keyword can be used to set P to a smaller value, which can be more efficient when running on a large number of processors.

The nfile keyword sets P to the specified Nf value. For example, if Nf = 4, and the simulation is running on 100 processors, 4 files will be written, by processors 0,25,50,75. Each will collect information from itself and the next 24 processors and write it to a restart file.

For the fileper keyword, the specified value of Np means write one file for every Np processors. For example, if Np = 4, every 4th processor (0,4,8,12,etc) will collect information from itself and the next 3 processors and write it to a restart file.

Restrictions: none

Related commands:

restart, read_restart

Default: none