The Computer Language
24.09 Benchmarks Game

pidigits Rust program

source code

// The Computer Language Benchmarks Game
// https://salsa.debian.org/benchmarksgame-team/benchmarksgame/
//
// Contributed by TeXitoi
// Inspired by Mr Ledrug's C version and thestinger's rust-gmp

#![allow(non_camel_case_types)]

//extern crate libc;
// exporting needed things from libc for linux x64 (still unstable)
#[cfg(all(target_os = "linux", any(target_arch = "x86_64", target_arch = "x86")))]
mod libc {
    #![allow(non_camel_case_types)]
    #[repr(u8)]
    pub enum c_void { __variant1, __variant2 }
    pub type c_int = i32;
    #[cfg(target_arch = "x86_64")] pub type c_ulong = u64;
    #[cfg(target_arch = "x86")] pub type c_ulong = u32;
}

use libc::{c_int, c_ulong, c_void};
use std::mem::uninitialized;
use std::cmp::Ordering;

fn main() {
    let n = std::env::args_os().nth(1)
        .and_then(|s| s.into_string().ok())
        .and_then(|n| n.parse().ok())
        .unwrap_or(27);
    for (i, d) in Context::new().enumerate().take(n) {
        print!("{}", d);
        if (i + 1) % 10 == 0 { println!("\t:{}", i + 1); }
    }
    if n % 10 != 0 {
        for _ in n % 10 .. 10 { print!(" "); }
        println!("\t:{}", n);
    }
}

pub struct Context {
    k: c_ulong,
    tmp1: Mpz,
    tmp2: Mpz,
    acc: Mpz,
    den: Mpz,
    num: Mpz
}
impl Context {
    pub fn new() -> Context {
        Context {
            k: 0,
            tmp1: Mpz::from_ui(0),
            tmp2: Mpz::from_ui(0),
            acc: Mpz::from_ui(0),
            den: Mpz::from_ui(1),
            num: Mpz::from_ui(1)
        }
    }
    fn extract_digit(&mut self, nth: c_ulong) -> c_ulong {
        self.tmp1.mul_ui(&self.num, nth);
        self.tmp2.add(&self.tmp1, &self.acc);
        self.tmp1.tdiv_q(&self.tmp2, &self.den);
        return self.tmp1.as_ui();
    }
    fn eliminate_digit(&mut self, d: c_ulong) {
        self.acc.submul_ui(&self.den, d);
        self.acc.mul_from_ui(10);
        self.num.mul_from_ui(10);
    }
    fn next_term(&mut self) {
        self.k += 1;
        let k2 = self.k * 2 + 1;
        self.acc.addmul_ui(&self.num, 2);
        self.acc.mul_from_ui(k2);
        self.den.mul_from_ui(k2);
        self.num.mul_from_ui(self.k);
    }
}
impl Iterator for Context {
    type Item = c_ulong;
    fn next(&mut self) -> Option<c_ulong> {
        loop {
            self.next_term();
            if self.num > self.acc { continue; }
            let d = self.extract_digit(3);
            if d != self.extract_digit(4) { continue; }

            self.eliminate_digit(d);
            return Some(d);
        }
    }
}

// safe bindings to needed GMP functions
pub struct Mpz {
    mpz: mpz_struct,
}
impl Drop for Mpz {
    fn drop(&mut self) { unsafe { __gmpz_clear(&mut self.mpz) } }
}
impl Mpz {
    pub fn from_ui(i: c_ulong) -> Mpz {
        unsafe {
            let mut mpz = uninitialized();
            __gmpz_init_set_ui(&mut mpz, i);
            Mpz { mpz: mpz }
        }
    }
    // self = a * b
    pub fn mul_ui(&mut self, a: &Mpz, b: c_ulong) {
        unsafe { __gmpz_mul_ui(&mut self.mpz, &a.mpz, b); }
    }
    // self *= a
    pub fn mul_from_ui(&mut self, a: c_ulong) {
        unsafe { __gmpz_mul_ui(&mut self.mpz, &self.mpz, a); }
    }
    // self -= a * b
    pub fn submul_ui(&mut self, a: &Mpz, b: c_ulong) {
        unsafe { __gmpz_submul_ui(&mut self.mpz, &a.mpz, b); }
    }
    // self = a + b
    pub fn add(&mut self, a: &Mpz, b: &Mpz) {
        unsafe { __gmpz_add(&mut self.mpz, &a.mpz, &b.mpz); }
    }
    // self += a * b
    pub fn addmul_ui(&mut self, a: &Mpz, b: c_ulong) {
        unsafe { __gmpz_addmul_ui(&mut self.mpz, &a.mpz, b); }
    }
    // self = a / b
    pub fn tdiv_q(&mut self, a: &Mpz, b: &Mpz) {
        unsafe { __gmpz_tdiv_q(&mut self.mpz, &a.mpz, &b.mpz); }
    }
    pub fn as_ui(&self) -> c_ulong {
        unsafe { __gmpz_get_ui(&self.mpz) }
    }
}
impl Eq for Mpz {}
impl PartialEq for Mpz {
    fn eq(&self, other: &Mpz) -> bool {
        unsafe { __gmpz_cmp(&self.mpz, &other.mpz) == 0 }
    }
}
impl Ord for Mpz {
    fn cmp(&self, other: &Mpz) -> Ordering {
        let cmp = unsafe { __gmpz_cmp(&self.mpz, &other.mpz) };
        if cmp == 0 {
            Ordering::Equal
        } else if cmp < 0 {
            Ordering::Less
        } else {
            Ordering::Greater
        }
    }
}
impl PartialOrd for Mpz {
    fn partial_cmp(&self, other: &Mpz) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

// Raw bindings to needed GMP functions
#[repr(C)]
struct mpz_struct {
    _mp_alloc: c_int,
    _mp_size: c_int,
    _mp_d: *mut c_void
}

type mpz_ptr = *mut mpz_struct;
type mpz_srcptr = *const mpz_struct;

#[link(name = "gmp")]
extern "C" {
    fn __gmpz_init_set_ui(rop: mpz_ptr, op: c_ulong);
    fn __gmpz_clear(x: mpz_ptr);
    fn __gmpz_get_ui(op: mpz_srcptr) -> c_ulong;
    fn __gmpz_cmp(op1: mpz_srcptr, op2: mpz_srcptr) -> c_int;
    fn __gmpz_add(rop: mpz_ptr, op1: mpz_srcptr, op2: mpz_srcptr);
    fn __gmpz_mul_ui(rop: mpz_ptr, op1: mpz_srcptr, op2: c_ulong);
    fn __gmpz_submul_ui(rop: mpz_ptr, op1: mpz_srcptr, op2: c_ulong);
    fn __gmpz_addmul_ui(rop: mpz_ptr, op1: mpz_srcptr, op2: c_ulong);
    fn __gmpz_tdiv_q(q: mpz_ptr, n: mpz_srcptr, d: mpz_srcptr);
}
    

notes, command-line, and program output

NOTES:
64-bit Ubuntu quad core
1.80.1
(3f5fd8dd4
2024-08-06)
LLVM version: 18.1.7


 Thu, 05 Sep 2024 22:51:43 GMT

MAKE:
/opt/src/rust-1.80.1/bin/rustc -C opt-level=3 -C target-cpu=ivybridge -C codegen-units=1  pidigits.rs -o pidigits.rust_run
warning: use of deprecated function `std::mem::uninitialized`: use `mem::MaybeUninit` instead
  --> pidigits.rs:22:15
   |
22 | use std::mem::uninitialized;
   |               ^^^^^^^^^^^^^
   |
   = note: `#[warn(deprecated)]` on by default

warning: use of deprecated function `std::mem::uninitialized`: use `mem::MaybeUninit` instead
   --> pidigits.rs:104:27
    |
104 |             let mut mpz = uninitialized();
    |                           ^^^^^^^^^^^^^

warning: the type `mpz_struct` does not permit being left uninitialized
   --> pidigits.rs:104:27
    |
104 |             let mut mpz = uninitialized();
    |                           ^^^^^^^^^^^^^^^
    |                           |
    |                           this code causes undefined behavior when executed
    |                           help: use `MaybeUninit<T>` instead, and only call `assume_init` after initialization is done
    |
note: integers must be initialized (in this struct field)
   --> pidigits.rs:164:5
    |
164 |     _mp_alloc: c_int,
    |     ^^^^^^^^^^^^^^^^
    = note: `#[warn(invalid_value)]` on by default

warning: 3 warnings emitted

rm pidigits.rs

7.46s to complete and log all make actions

COMMAND LINE:
 ./pidigits.rust_run 10000

(TRUNCATED) PROGRAM OUTPUT:
3141592653	:10
5897932384	:20
6264338327	:30
9502884197	:40
1693993751	:50
0582097494	:60
4592307816	:70
4062862089	:80
9862803482	:90
5342117067	:100
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1328230664	:120
7093844609	:130
5505822317	:140
2535940812	:150
8481117450	:160
2841027019	:170
3852110555	:180
9644622948	:190
9549303819	:200
6442881097	:210
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5271201909	:250
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