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[Caml-list] Bigarray access speed
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 Date: 2002-08-15 (22:50) From: Richard Nyberg Subject: [Caml-list] Bigarray access speed
```In the following small programs 3) is faster than 1) and 2), which run
equally fast. However, 4 is significantly slower than the rest. If you
change the line "a.{i} <- a.{i} + i" to "a.{i} <- i" the execution time
is halfed but it's still much slower.

Are access to Bigarrays slower when passed to functions? If so, is it
fixable? or is there some workaround?

I stumbled upon this while coding on a school assignment ((not too ;) fast
multiplication of large integers).

1)
let a = Array.make 1000000 0 in
for i = 0 to 999999 do
a.(i) <- a.(i) + i;
done;;

2)
let a = Array.make 1000000 0 in
let rec loop a i =
if i <= 999999 then begin
a.(i) <- a.(i) + i;
loop a (i + 1)
end in
loop a 0;;

3)
open Bigarray;;
let a = Array1.create int c_layout 1000000 in
Array1.fill a 0;
for i = 0 to 999999 do
a.{i} <- a.{i} + i
done;;

4)
open Bigarray;;
let a = Array1.create int c_layout 1000000 in
Array1.fill a 0;
let rec loop a i =
if i <= 999999 then begin
a.{i} <- a.{i} + i;
loop a (i + 1)
end in
loop a 0;;

-Richard
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