From 8ba76c7a00467d7fbc22e0e0d34204a94cd4469f Mon Sep 17 00:00:00 2001
From: Quaternions <krakow20@gmail.com>
Date: Thu, 29 Aug 2024 12:12:14 -0700
Subject: [PATCH] smarter sqrt

---
 fixed_wide/src/fixed.rs | 28 ++++++++++------------------
 1 file changed, 10 insertions(+), 18 deletions(-)

diff --git a/fixed_wide/src/fixed.rs b/fixed_wide/src/fixed.rs
index 83125b3..0030361 100644
--- a/fixed_wide/src/fixed.rs
+++ b/fixed_wide/src/fixed.rs
@@ -289,25 +289,17 @@ impl<const CHUNKS:usize,Frac:Unsigned> Fixed<CHUNKS,Frac>
 		Fixed::<CHUNKS,Frac>:std::ops::Mul<Fixed<CHUNKS,Frac>,Output=Fixed<CHUNKS,Frac>>,
 {
 	pub fn sqrt_unchecked(self)->Self{
-		//find pow2 more powerful than self
-		let mut pow2=if Self::ONE<self{
-			let mut pow2=Self::TWO;//1<self is so bake one iteration
-			while pow2<=self{
-				pow2<<=1;
-			}
-			pow2
-		}else if Self::ONE==self{
-			return Self::ONE;
-		}else if Self::ZERO<self{
-			let mut pow2=Self::ONE;
-			while self<=pow2{
-				pow2>>=1;
-			}
-			pow2
-		}else{//either 0==self or self is negative
-			return Self::ZERO;
+		//pow2 must be the minimum power of two which when squared is greater than self
+		//0001.0000 Fixed<u8,4>
+		//sqrt
+		//0110.0000
+		//pow2 = 0100.0000
+		let mut pow2=Self{
+			bits:BInt::<CHUNKS>::ONE.shl((((CHUNKS as i32*64-Frac::I32-(self.bits.leading_zeros() as i32)+1)>>1)+Frac::I32) as u32),
+			frac:PhantomData,
 		};
-		let mut result=pow2;
+		let mut result=pow2>>1;
+
 		while pow2!=Self::ZERO{
 			pow2>>=1;
 			let new_result=result+pow2;