It may be a good idea to prealocate the whole array so you don't resize the dynamic arrays every execution of the loop.

2015-05-11 23:30 GMT+02:00 weaselcat via Digitalmars-d <digitalmars-d@puremagic.com>:
On Monday, 11 May 2015 at 21:15:33 UTC, Dzhon Smit wrote:
...

time sbcl --dynamic-space-size 4GB --script fib.lisp
0
 1.16user 1.49system 0:02.67elapsed 99%CPU (0avgtext+0avgdata 1658860maxresident)k

ldc -O5 -release -boundscheck=off fib.d
$ time ./fib
0
1.33user 0.81system 0:02.15elapsed 99%CPU (0avgtext+0avgdata 1230712maxresident)k