From 3f381e3c0cd381871089f930d2c5a1cedac78f88 Mon Sep 17 00:00:00 2001
From: trivernis <trivernis@protonmail.com>
Date: Fri, 27 Nov 2020 18:44:23 +0100
Subject: [PATCH] Change algorithm to use cached values only

Signed-off-by: trivernis <trivernis@protonmail.com>
---
 src/kernel_controller/kernel.cl | 35 +++++++++++++++++----------------
 src/kernel_controller/mod.rs    | 21 +++++++++++++-------
 src/main.rs                     |  1 +
 3 files changed, 33 insertions(+), 24 deletions(-)

diff --git a/src/kernel_controller/kernel.cl b/src/kernel_controller/kernel.cl
index 8300507..053579d 100644
--- a/src/kernel_controller/kernel.cl
+++ b/src/kernel_controller/kernel.cl
@@ -5,40 +5,41 @@
  */
 
 
-__kernel void check_prime(const uint LOWER_PRIME_COUNT, __global const ulong *LOWER_PRIMES, __global const ulong *IN, __global bool *OUT) {
+__kernel void check_prime_cached(const uint LOWER_PRIME_COUNT, __global const ulong *LOWER_PRIMES, __global const ulong *IN, __global bool *OUT) {
     uint id = get_global_id(0);
     ulong num = IN[id];
-    bool prime = true;
     ulong limit = (ulong) native_sqrt((double) num) + 1;
 
     if (num < 3 || num % 2 == 0) {
-        prime = false;
+        return;
     } else {
         for (uint i = 0; i < LOWER_PRIME_COUNT; i++) {
             if (LOWER_PRIMES[i] >= limit) {
                 break;
             }
             if (num % LOWER_PRIMES[i] == 0) {
-                prime = false;
-                break;
+                return;
             }
         }
-        ulong start = LOWER_PRIMES[LOWER_PRIME_COUNT - 1];
+    }
 
-        if (prime && start < limit) {
-            start -= start % 3;
+    OUT[id] = true;
+}
 
-            if (start % 2 == 0) {
-                start -= 3;
-            }
-            for (ulong i = start; i <= limit; i += 6) {
-                if (num % (i - 2) == 0 || num % (i - 4) == 0) {
-                    prime = false;
-                    break;
-                }
+__kernel void check_prime(__global const ulong *IN, __global bool *OUT) {
+    uint id = get_global_id(0);
+    ulong num = IN[id];
+    ulong limit = (ulong) native_sqrt((double) num) + 1;
+
+    if (num < 3 || num % 2 == 0) {
+        return;
+    } else {
+        for (ulong i = 9; i <= limit; i += 6) {
+            if (num % (i - 2) == 0 || num % (i - 4) == 0) {
+                return;
             }
         }
     }
 
-    OUT[id] = prime;
+    OUT[id] = true;
 }
\ No newline at end of file
diff --git a/src/kernel_controller/mod.rs b/src/kernel_controller/mod.rs
index 1781292..fdd9ab6 100644
--- a/src/kernel_controller/mod.rs
+++ b/src/kernel_controller/mod.rs
@@ -46,7 +46,12 @@ impl KernelController {
     }
 
     pub fn filter_primes(&self, input: Vec<u64>) -> ocl::Result<Vec<u64>> {
-        lazy_static::lazy_static! {static ref PRIME_CACHE: Arc<Mutex<Vec<u64>>> = Arc::new(Mutex::new(get_primes(2048)));}
+        lazy_static::lazy_static! {static ref PRIME_CACHE: Arc<Mutex<Vec<u64>>> = Arc::new(Mutex::new(Vec::new()));}
+        if PRIME_CACHE.lock().len() == 0 {
+            PRIME_CACHE.lock().append(&mut get_primes(
+                (*input.iter().max().unwrap_or(&1024) as f64).sqrt().ceil() as u64,
+            ));
+        }
 
         let prime_buffer = self
             .pro_que
@@ -68,7 +73,7 @@ impl KernelController {
 
         let kernel = self
             .pro_que
-            .kernel_builder("check_prime")
+            .kernel_builder("check_prime_cached")
             .arg(prime_buffer.len() as u32)
             .arg(&prime_buffer)
             .arg(&input_buffer)
@@ -120,15 +125,17 @@ impl KernelController {
 }
 
 /// Returns a list of prime numbers that can be used to speed up the divisibility check
-fn get_primes(count: usize) -> Vec<u64> {
+fn get_primes(max_number: u64) -> Vec<u64> {
     let start = Instant::now();
-    let mut primes = Vec::with_capacity(count);
+    let mut primes = Vec::with_capacity((max_number as f64).sqrt() as usize);
     let mut num = 3;
 
-    while primes.len() < count {
+    while num < max_number {
         let mut is_prime = true;
 
-        if num < 3 || num % 2 == 0 {
+        if num == 2 {
+            is_prime = true;
+        } else if num < 3 || num % 2 == 0 {
             is_prime = false;
         } else {
             let check_stop = (num as f64).sqrt().ceil() as u64;
@@ -162,7 +169,7 @@ fn get_primes(count: usize) -> Vec<u64> {
     }
     println!(
         "Generated {} primes on the cpu in {} ms",
-        count,
+        primes.len(),
         start.elapsed().as_secs_f64() * 1000f64
     );
 
diff --git a/src/main.rs b/src/main.rs
index 66965ea..09585f3 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -78,6 +78,7 @@ fn calculate_primes(prime_opts: CalculatePrimes, controller: KernelController) -
     if offset % 2 == 0 {
         offset += 1;
     }
+    sender.send(vec![2]).unwrap();
     loop {
         let start = Instant::now();
         let numbers = (offset..(prime_opts.numbers_per_step as u64 * 2 + offset))