Implement a "checkpointing" option for simulate

[Christian Speckner]

Implement a local "checkpoint = n" option for simulate which makes WHIZARD print out the event generation status (events generated, events remaining, etc...) each n events.

[Christian Speckner]

Done in r2354, fixing on the fly the ?rebuild_events which was broken (aka ignored). It is now possible to set the integer variable "checkpoint = n" resulting to generate status output every n events (the feature is disabled by default). For example, the input file

model = SM

process test = "e+", "e-" => "W+", "W-"

compile

sqrts = 500 GeV
integrate (test)

simulate (test) {
        ?rebuild_events = true
        n_events = 356
        checkpoint = 50
}

will result in

?rebuild_events = true
n_events =          356
checkpoint =           50
| Initializating simulation for processes test:
| Simulation mode = unweighted, event_normalization = '1'
| No analysis setup has been provided.
| Generating 356 events ...
| Writing events in internal format to file 'test.evx'
| Event sample corresponds to luminosity [fb-1] =   0.4944E-01
|
| |==================================================|
| | % complete | events generated | events remaining |
| |==================================================|
|      0.0               0                356
|     14.0              50                306
|     28.1             100                256
|     42.1             150                206
|     56.2             200                156
|     70.2             250                106
|     84.3             300                 56
|     98.3             350                  6
|    100.0             356                  0
| |==================================================|
|
| ... done