During runtime, preCICE writes different output files. On this page, we give an overview of these files and their content.

If the participant’s name is MySolver, preCICE creates the following files:

## precice-MySolver-iterations.log

Information per time window with number of coupling iterations etc. (only for implicit coupling). In case you use a quasi-Newton acceleration, this file also contains information on the state of the quasi-Newton system.

An example file:

TimeWindow  TotalIterations  Iterations  Convergence  QNColumns  DeletedQNColumns  DroppedQNColumns
1       5       5       1       0       0       0
2      10       5       1       0       0       0
3      15       5       1       0       0       0
4      20       5       1       0       0       0
5      24       4       1       0       0       0
6      28       4       1       0       0       0
7      32       4       1       0       0       0
...

• TimeWindow is the time window counter.
• TotalIterations is the total (summed up) number of coupling iterations.
• Iterations is the number of iterations preCICE used in each time window.
• Convergence indicates whether the coupling converged (1) or not (0) in each time window.
• QNColumns gives the amount of columns in the tall-and-skinny matrices V and W after convergence.
• DeletedQNColumns gives the amount of columns that were filtered out during this time window (due to a QR filter). In this example no columns were filtered out.
• DroppedQNColumns gives the amount of columns that went out of scope during this time window (due to max-iterations or time-windows-reused). Here, for example, 5 columns went out of scope during the 6th time window.

## precice-MySolver-convergence.log

Information per iteration with current residuals (only for second participant in an implicit coupling).

An example file:

TimeWindow  Iteration  ResRel(Temperature)  ResRel(Heat-Flux)
1       1  1.00000000e+00  1.00000000e+00
1       2  2.36081866e-03  4.61532554e-01
1       3  1.76770050e-03  2.20718535e-03
1       4  8.24839318e-06  4.83731693e-04
1       5  1.38649284e-06  3.03987119e-05
2       1  2.02680329e-03  1.14463674e+00
2       2  1.10152875e-03  4.53255279e-01
...

• TimeWindow is the time window counter.
• Iteration is the coupling iteration counter within each time window. So, in the first time window, 6 iterations were necessary to converge, in the second time window 3.
• And then two convergence measure are defined in the example. Two relative ones – hence the ...Rel(...). The two columns ResRel(Temperature) and RelRel(Force) give the relative residual for temperature and heat flux, respectively, at the start of each iteration.

## precice-MySolver-events.json

Recorded events with timestamps. See page on performance analysis.

## precice-MySolver-events-summary.log

Summary of all events timings. See page on performance analysis.

## precice-postProcessingInfo.log

Advanced information on the numerical performance of the Quasi-Newton coupling (if used and enabled)

In preCICE v1.3.0 and earlier, instead of precice-MySolver-events.json, two performance output files were used: precice-MySolver-events.log and precice-MySolver-eventTimings.log.

In preCICE v1.2.0 and earlier, slightly different names were used: iterations-MySolver.txt,convergence-MySolver.txt, Events-MySolver.log,EventTimings-MySolver.log, and postProcessingInfo.txt.