3. Restart and terminate PHITS calculations

3.1. Restart PHITS calculations

If tally results of PHITS calculations are not statistically significant enough, PHITS is able to read the previous tally results and resume the calculations (restart calculation mode). In the [parameters] section, restart calculation mode can be activated by setting istdev < 0, and the statistics of the restart calculation will be counted together with the previous tally results. It is allowed to add new tally sections for the input file with the restart calculation, even if there is no past tally result. Please refer to the description of istdev in the [parameters] section.

The procedure of restart calculation is described as follows:

  1. Check whether or not the file specified by resfile in each tally section exists. The default file name of the resfile is that given by file parameter.

  2. If there is no resfile for a tally, it is regarded as new. If no resfile can be found for any tally, a new calculation is begun with istdev=|istdev|.

  3. If resfile exists, PHITS reads information from the file on the standard deviation mode istdev, total weight resc2, total history number resc3, history number per batch maxcas, the next random seed rijklst, and the results and relative errors of the past calculation.

  4. The tally parameters given in the current and past PHITS input files are then checked for consistency. If they are not consistent with each other, PHITS stops the calculation and outputs an error message. It should be noted that not all tally parameters are checked for consistency in this process.

  5. (In batch standard deviation mode only) The consistency of istdev and maxcas among the resfiles is checked. If they are consistent, the restart calculation is performed using these values. If an inconsistency is found, the calculation is stopped.

  6. The initial random seed is changed to the value of rijklst obtained from the first resfiles. If rijklst differs by resfile, a warning message is output.

  7. Upon finishing the restart calculation, the tally results are output to the file specified by file=. If resfile is not specified, the past tally results are overwritten.

Important notice:

  1. All past tally results should be calculated in the same standard deviation mode: i.e., istdev should be the same in all resfile.

  2. The maxcas written in the input file is not used in the restart calculation in batch standard deviation mode.

  3. Except for those given in the tally sections, the consistencies of input parameters are not checked by the PHITS program. If they are inconsistent with the previous setting, the tally results might be incorrect even if no error messages show up.

3.2. Terminate the PHITS code

Once PHITS is executed, it creates a batch.out [1] file following every batch that contains elapse information. In parallel calculation, batch.out also contains each processor element (PE) status. The occurrence of a PE abort can be determined by examining batch.out.

The first line of batch.out is written as follows:

10 <--- number of remaining batches

Here, the value on the left is the number of remaining batches at the moment. The remaining batches can be reduced by editing the value and saving batch.out. For example, when the value is changed to 3, the PHITS execution will be terminated after the calculation of three batches is finished. Changing the value to 0 terminates the code execution right after the calculation of that batch is completed. This function can be useful in the way explained below.

The parameter itall can be used together with batch.out. If itall=0(default) or itall=1 is set in the [parameters] section, PHITS will update the calculation results (tally output) at the end of each batch. With itall=1, the image (*.eps) files will also be updated. In parallel computing mode, the results are updated every batch \(\times\) (PE - 1). Using these functions enables terminating PHITS calculations at any time with the latest results updated.

From ver. 2.86, the file name of batch.out can be modified by setting file(22) in the [parameters] section. Changing the name of each input file enables multiple executions of PHITS in a common directory. Note that this function is not available if [t-dchain] is set in the input files, because the same file name, n.flux, is used.

The value of rijk written in the batch.out file is the initial random number of the current batch. Thus, for example, in cases of unsuccessful termination of PHITS, it is possible to reproduce the calculation of the specified batch using the value of rijk.