ProgressReporter is a simple utility to help keep track of progress
in a long iterative computation; it prints out a short "progress
report" at roughly the indicated time intervals.
To respect the chosen time interval ProgressReporter assumes that
successive iterations do not vary wildly in computational cost.
ProgressReporter(t) -- create a reporter which prints at intervals of roughly t seconds (t is a double)
There is essentially one operation: let report be a ProgressReporter
report() -- print a progress report if enough time has elapsed
report(arg1) -- print a progress report (incl. value of arg1 of type long) if enough time has elapsed
report(arg1, arg2) -- print a progress report (incl. values of arg1, arg2 of type long)
if enough time has elapsed
These calls are designed to be cheap when it is not time to produce a report.
The only "tricky part" was trying to make reports appear at round values of the internal counter. It is a little messy, but not hard.
The mem fns operator() are inline so that most non-printing calls should
be very cheap. It seems useful to let the user supply some extra values to
be printed.
increase125 increases its arg to next number of the form 10^n, 2*10^n or
5*10^n; decrease125 decreases the arg to the next lowest number of that
form.
Initially I tried to make the printed times close to multiples of the specified interval, but this led to "surprising" behaviour if some CPU time had been used before starting the loop -- the first report could be printed after much less than the chosen interval (and the corresponding number of iterations would be much smaller than expected). Now the code simply says next print time is one interval from the previous print time (so average print intervals will be slightly longer than desired).
Should increase125 and decrease125 be moved to utils?
2014