Re: [Caml-list] Divide and print with precision

[Drup <drupyog+caml@zoho.com>]

Why do you use Gmp ? Zarith already uses GMP under the hood and you can 
use the Q module for arbitrary precision rationals.

Le 15/10/2014 11:22, Marek Kubica a écrit :
> Hello,
>
> I've got this short program here:
>
> let prec = 1_000_000
> let max_n = 205_211
> let to_string = Gmp.F.to_string_base_digits ~base:10 ~digits:0
>
> let euler_fraction n =
>    let open Z in
>    let numerator = ref one in
>    let denominator = ref one in
>    for i = 1 to n do
>      numerator := succ (!numerator * (of_int i));
>      denominator := (of_int i) * !denominator;
>    done;
>    (!numerator, !denominator)
>
> let f () =
>    let (num, den) = euler_fraction max_n in
>    let znum = Gmp.F.from_string (Z.to_string num) in
>    let zden = Gmp.F.from_string (Z.to_string den) in
>    let euler = Gmp.F.div_prec ~prec znum zden in
>    print_endline @@ to_string euler
>
> let () = f ()
>
> It just computes e, using Zarith and Gmp. While Zarith works splendid,
> I am having problems getting the division to work. I mean, it does
> work, but I don't know how precise it is, because I can't get mlgmp to
> print the 1_000_000 digits. From what I read in the GMP docs, 0 digits
> means "whatever precision is available" but even if I explicitly
> specify 1000 digits or so, the output is always
> "2.718281828459045235360287471352662497757E0".
>
> What can I do to get longer output? I don't insist on mlgmp (in fact,
> it leaks memory like crazy, before I used Zarith I used mlgmp which
> used 12 GB of RAM before I killed it), I just want some way to get a
> base-10 floating point representation of my number.
>
> Hope someone knows a solution.
>
> regards,
> Marek
>