yggdrasil/num-bigint-dig
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Update partial.rs

Browse Source
This commit is contained in:
goldenMetteyya 2019-04-09 23:49:51 +03:00
parent 10fcc8b683
commit 1962227e32
1 changed files with 33 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

64
src/algorithms/partial.rs
View File

@ -31,35 +31,37 @@ fn signed_shift(op: u64, shift: i32) -> u64 {
//https://github.com/thomaso-mirodin/intmath/blob/master/u64/log2.go#L5
// Log2 returns log base 2 of n. It's the same as index of the highest
// bit set in n. n == 0 returns 0
// fn Log2(n: u64) -> u64 {
// // Using uint instead of uint64 is about 25% faster
// // on x86 systems with the default Go compiler.
// var r, v uint
// if n < 1<<32 {
// v = uint(n)
// } else {
// r = 32
// v = uint(n >> 32)
// }
// if v >= 1<<16 {
// r += 16
// v >>= 16
// }
// if v >= 1<<8 {
// r += 8
// v >>= 8
// }
// if v >= 1<<4 {
// r += 4
// v >>= 4
// }
// if v >= 1<<2 {
// r += 2
// v >>= 2
// }
// r += v >> 1
// return uint64(r)
// }
fn u64_log2(n: u64) -> u64 {
// Using uint instead of uint64 is about 25% faster
// on x86 systems with the default Go compiler.
let mut r: usize = 0;
let mut _v: usize = 0;
if n < 1<<32 {
_v = n as usize;
} else {
r = 32;
_v = (n >> 32) as usize;
}
if _v >= 1<<16 {
r += 16;
_v >>= 16;
}
if _v >= 1<<8 {
r += 8;
_v >>= 8;
}
if _v >= 1<<4 {
r += 4;
_v >>= 4;
}
if _v >= 1<<2 {
r += 2;
_v >>= 2;
}
r += _v >> 1;
return r as u64;
}
//Port to rust from c++
@ -82,8 +84,8 @@ pub fn partial_bigint(op: &BigInt) -> (i64, i32) {
//let lg2: f64 = (last as f64).log2() + 1.0;
// // extract the top word of bits from a and b
// let h = a.digits()[n - 1].leading_zeros();
let lg2 = last.leading_zeros();
//let lg2 = last.leading_zeros();
let lg2 = u64_log2(last);
let mut exp = lg2 as i32;