Jarrett Billingsley wrote:
Performance of dynamic arrays is the same no matter where their data is. Fixed-size 2D arrays are not faster _because_ they are on the stack, they just happen to be allocated on the stack. They are faster (usually) because they don't need two pointer dereferences. You can allocated a fixed-size 2D array on the heap (well.. inside a struct or class anyway) and it will be just as fast.
Your "usually" interests me. I was under the impression, and it seems quite logical, that static arrays are faster than dynamic ones. However, recently I did some simple experiments with matrix operations (multiplication, etc.), in which performance was actually a little bit better for dynamic arrays.
Is there a general "rule" for when dynamic arrays are faster than static ones, and vice versa?
Also, I tried multiplying large matrices both using arrays in D and using a C BLAS implementation. The BLAS algorithm is the same as the one I've written in D, and additionally includes a lot of runtime checks. Still, multiplication using BLAS was about four times faster. Is this simply because C compilers are a lot better at optimisation than the D compilers?
-Lars
