Use imported primes.

src/candidate.rs

@@ -18,6 +18,7 @@
 
 pub struct CandidateGenerator {
 	base:u64,
+	// first use of the base
 	first_use:bool,
 }
 
@@ -29,6 +30,27 @@ impl CandidateGenerator {
 		}
 	}
 
+	pub fn calc_base(&mut self, last_prime:u64) {
+		if last_prime == 2 {
+			self.base = 0;
+			self.first_use = false;
+		} else if last_prime == 3 {
+			self.base = 6;
+			self.first_use = true;
+		} else {
+			let modulo = last_prime % 6;
+			if modulo == 1 {
+				self.base = last_prime + 5;
+				self.first_use = true;
+			} else if modulo == 5 {
+				self.base = last_prime + 1;
+				self.first_use = false;
+			} else {
+				panic!("Invalid last prime {}" , last_prime);
+			}
+		}
+	}
+
 	pub fn next(&mut self) -> u64 {
 		/*
 		 * All primes, except 2 and 3, will be equal to (n * 6 ± 1). This avoids

src/main.rs

@@ -79,6 +79,9 @@ fn main() {
 		println!("{}", res);
 	} else {
 		let mut cand_gen = CandidateGenerator::new();
+		if !primes_list.borrow().is_empty() {
+			cand_gen.calc_base(*primes_list.borrow().back().unwrap());
+		}
 
 		loop {
 			let cand = cand_gen.next();