24 September, 2011

♫ if i could turn back time ♪

Cooker has a one-way-only knob for setting time. You wind forwards until you reach now. If you miss now, you wind forwards another 24h (luckily the cooker doesn't have a date too) until you reach now again. On TZ shift (i.e. end/start of summertime / daylight savings), once per year, there's a wind-forward 1h event. fairly easy. you make the clock run faster than real time. but once per year there's a once per year wind-forward 23h event. BUT! Turns out if you can stop the clock, then you can let real time wind forwards faster than clock time. and wait an hour. and then start the clock again. It involves more real time (you have to wait an hour) but a lot less tedious winding.

17 September, 2011

10 September, 2011

5 centuries ago...

I just queued up jobs for a physics simulation that are 5 compute-centuries long:

6 jobs x 11.5 hours x 16384 nodes x 4 cores/node = 5.16 centuries.

I'm expecting the runs to be finished in about a week

If this ran on a single core and I wanted it to be finishing in about a week, I would have had to start them in the year 1495 (the most interesting wikipedia note for that year is Friar John Cor records the first known batch of Scotch whisky).

03 September, 2011

frustrated-with-slow-simulation haiku

microseconds pass
simulation time stretched
long as winters night

I can't complain too much though - this was 65536 cores on an IBM BlueGene/P