Reserving capacity in associative arrays

[Jon D via Digitalmars-d-learn]

Is there a way to reserve capacity in associative arrays? In some 
programs I've been writing I've been getting reasonable 
performance up to about 10 million entries, but beyond that 
performance is impacted considerably (say, 30 million or 50 
million entries). GC stats (via the "--DRT-gcopt=profile:1" 
option) indicate dramatic increases in gc time, which I'm 
assuming comes from resizing the underlying hash table. I'm 
guessing that by preallocating a large size the performance 
degradation would not be quite so dramatic. The underlying 
implementation of associative arrays appears to take an initial 
number of buckets, and there's a private resize() method, but 
it's not clear if there's a public way to use these.

--Jon