On May 27, 1:17 am, Per Bothner <[email protected]> wrote:
> This is another example of where structs would be helpful. That would
> allow:
>
> struct Integer {
> int ivalue;
> int[] iwords;
>
> }
....
>
> Kawa basically does this using a regular class gnu.math.Integer,
> and "small" Integers pre-allocated. That is one reason Kawa's
> arbitrary-precision handling is (mostly) noticeably faster than BigInteger.
> (Some of that could be achieved by further tweaking BigInteger.)
1: I'm intrigued. How much does this give you?
I can see that you avoid a virtual call for all math operators where
you can determine the integer-ness of operands; so it does not have to
choose between SmallInt and BigInt objects. But it comes at the
overhead of an extra word per integer.
Integer arithmetic (most notably X+1, X-1, and X==<constant>) used in
loops is currently a noticeable performance issue in Erjang (when
comparing to the normal erlang implementation using tags). In many
such cases, I could avoid a virtual call and that does sound
appealing.
2: What is the motivation in Kawa to make your own bignum
implementation. Why not just have
class KawaInteger {
int ival;
BigInteger bval;
...
}
i.e., fall back on the standard bignum implementation?
Kresten
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