Sampling algorithms for D

[Joseph Rushton Wakeling]

On 13/04/12 01:44, bearophile wrote:
> final size_t select(ref UniformRNG urng)
> in {
>      assert(_recordsRemaining>  0);
>      assert(_sampleRemaining>  0);
> } body {
>      ...
> }

OK.  I'm confused by these asserts, because if I go beyond what is acceptable by 
calling select() even after I've collected a complete sample, no error is 
thrown.  e.g. if I put in place a function:

void sampling_test_simple(SamplerType, UniformRNG)
                          (size_t records, size_t samples, ref UniformRNG urng)
{
       auto s = new SamplerType(records,samples,urng);
       while(s.sampleRemaining > 0) {
             write("\trecord selected: ", s.select(urng), ".");
             write("\trecords remaining: ", s.recordsRemaining, ".");
             writeln("\tstill to sample: ", s.sampleRemaining, ".");
       }
       // Let's see if we can bust this ...

       writeln("Selecting 1 more just for luck: ", s.select(urng), ", records 
remaining: ", s.recordsRemaining, ", still to sample: ", s.sampleRemaining);
       writeln("Selecting 1 more just for luck: ", s.select(urng), ", records 
remaining: ", s.recordsRemaining, ", still to sample: ", s.sampleRemaining);
       writeln("Selecting 1 more just for luck: ", s.select(urng), ", records 
remaining: ", s.recordsRemaining, ", still to sample: ", s.sampleRemaining);
       writeln("Selecting 1 more just for luck: ", s.select(urng), ", records 
remaining: ", s.recordsRemaining, ", still to sample: ", s.sampleRemaining);
       writeln("Selecting 1 more just for luck: ", s.select(urng), ", records 
remaining: ", s.recordsRemaining, ", still to sample: ", s.sampleRemaining);
       writeln("Selecting 1 more just for luck: ", s.select(urng), ", records 
remaining: ", s.recordsRemaining, ", still to sample: ", s.sampleRemaining);
       writeln("Selecting 1 more just for luck: ", s.select(urng), ", records 
remaining: ", s.recordsRemaining, ", still to sample: ", s.sampleRemaining);
       writeln("Selecting 1 more just for luck: ", s.select(urng), ", records 
remaining: ", s.recordsRemaining, ", still to sample: ", s.sampleRemaining);
       writeln("Selecting 1 more just for luck: ", s.select(urng), ", records 
remaining: ", s.recordsRemaining, ", still to sample: ", s.sampleRemaining);
}

(... see current GitHub code: https://github.com/WebDrake/SampleD )

It doesn't make any difference if I compile with -debug enabled:

    gdmd -debug -oftest sampled.d