StrafesNET/fixed_wide_vectors
3
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

further sqrt improvements

Browse Source
This commit is contained in:
Quaternions 2024-08-29 13:15:17 -07:00
parent e684fb421e
commit 6ea9eff844
1 changed files with 27 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

31
fixed_wide/src/fixed.rs
View File

@ -18,6 +18,15 @@ impl<const CHUNKS:usize,Frac:Unsigned> Fixed<CHUNKS,Frac>{
pub const NEG_ONE:Self=Self{bits:BInt::<CHUNKS>::NEG_ONE.shl(Frac::U32),frac:PhantomData};
pub const NEG_TWO:Self=Self{bits:BInt::<CHUNKS>::NEG_TWO.shl(Frac::U32),frac:PhantomData};
pub const NEG_HALF:Self=Self{bits:BInt::<CHUNKS>::NEG_ONE.shl(Frac::U32-1),frac:PhantomData};
pub const fn from_bits(bits:BInt::<CHUNKS>)->Self{
Self{
bits,
frac:PhantomData,
}
}
pub const fn to_bits(self)->BInt<CHUNKS>{
self.bits
}
}
impl<const CHUNKS:usize,Frac:Unsigned,T> From<T> for Fixed<CHUNKS,Frac>
@ -290,6 +299,13 @@ impl<const CHUNKS:usize,Frac:Unsigned> Fixed<CHUNKS,Frac>
{
pub fn sqrt_unchecked(self)->Self{
//pow2 must be the minimum power of two which when squared is greater than self
//the algorithm:
//1. count "used" bits to the left of the decimal
//2. add one
//This is the power of two which is greater than self.
//3. divide by 2 via >>1
//4. add on fractional offset
//Voila
//0001.0000 Fixed<u8,4>
//sqrt
//0110.0000
@ -300,14 +316,21 @@ impl<const CHUNKS:usize,Frac:Unsigned> Fixed<CHUNKS,Frac>
};
let mut result=pow2>>1;
while pow2!=Self::ZERO{
loop{
pow2>>=1;
if pow2==Self::ZERO{
break result;
}
//TODO: flip a single bit instead of adding a power of 2
let new_result=result+pow2;
if new_result*new_result<=self{
result=new_result;
//note that the implicit truncation in the multiply
//means that the algorithm can return a result which squares to a number greater than the input.
match self.cmp(&(new_result*new_result)){
core::cmp::Ordering::Less=>continue,
core::cmp::Ordering::Equal=>break new_result,
core::cmp::Ordering::Greater=>result=new_result,
}
}
result
}
pub fn sqrt(self)->Self{
if self<Self::ZERO{