From ba3478e6ce2b22d3aca95f40918953ccb3fd5831 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nicol=C3=A1s=20Ortega=20Froysa?= <nicolas@ortegas.org>
Date: Wed, 10 Dec 2025 13:12:49 +0100
Subject: [PATCH] Optimize marking of known composites.

---
 src/worker.rs | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/src/worker.rs b/src/worker.rs
index 033925c..886bb87 100644
--- a/src/worker.rs
+++ b/src/worker.rs
@@ -30,11 +30,14 @@ pub fn work_segment(known_primes:&Vec<u64>, start:usize, end:usize) -> Vec<u64>
 
 	for p in known_primes {
 		let prime = *p as usize;
-		let mut mult = prime * prime;
+		let modu = start % prime;
+		let mut mult = if modu == 0 {
+			start
+		} else {
+			start + prime - modu
+		};
 		while mult < end {
-			if mult > start {
-				sieve[mult - start] = false;
-			}
+			sieve[mult - start] = false;
 			mult += prime;
 		}
 	}