From 84c3f80ab077f71f2b0f8e5fde67cd8b7ae696ba Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=B6rg=20Sommer?= <joerg@alea.gnuu.de>
Date: Mon, 8 May 2017 11:03:54 +0200
Subject: [PATCH] euler87: Rust und C durch Schleifentausch beschleunigen
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Wenn man die innere (hoch 4) und die äußere Schleife (hoch 2) tauscht,
wird das C-Programm ca. 10% und das Rust-Programm ca. 25% schneller.
---
 2017-03-28/jo-so_euler87.c  | 16 +++++++++-------
 2017-03-28/jo-so_euler87.rs | 13 ++++++++-----
 2 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/2017-03-28/jo-so_euler87.c b/2017-03-28/jo-so_euler87.c
index 5c0a6d7..43fd23c 100644
--- a/2017-03-28/jo-so_euler87.c
+++ b/2017-03-28/jo-so_euler87.c
@@ -104,22 +104,24 @@ int main(void)
     vector_uint nums;
     vector_init(&nums);
 
-    for (uint* pn2 = prime_numbers; pn2 < prime_numbers_end; ++pn2)
+    for (uint* pn4 = prime_numbers; pn4 < prime_numbers_end; ++pn4)
     {
-        uint pow2 = *pn2 * *pn2;
+        uint pow4 = *pn4 * *pn4;
+        pow4 *= pow4;
+        if (pow4 >= LIMIT)
+            break;
 
         for (uint* pn3 = prime_numbers; pn3 < prime_numbers_end; ++pn3)
         {
-            uint sum = pow2 + *pn3 * *pn3 * *pn3;
+            uint sum = pow4 + *pn3 * *pn3 * *pn3;
             if (sum >= LIMIT)
                 break;
 
-            for (uint* pn4 = prime_numbers; pn4 < prime_numbers_end; ++pn4)
+            for (uint* pn2 = prime_numbers; pn2 < prime_numbers_end; ++pn2)
             {
-                uint pow4 = *pn4 * *pn4;
-                pow4 *= pow4;
+                uint pow2 = *pn2 * *pn2;
 
-                uint sum2 = sum + pow4;
+                uint sum2 = sum + pow2;
                 if (sum2 >= LIMIT)
                     break;
 
diff --git a/2017-03-28/jo-so_euler87.rs b/2017-03-28/jo-so_euler87.rs
index c5611e1..ba819d8 100644
--- a/2017-03-28/jo-so_euler87.rs
+++ b/2017-03-28/jo-so_euler87.rs
@@ -35,17 +35,20 @@ fn main() {
 
     let mut nums = Vec::new();
 
-    for pn2 in pn.iter() {
-        let pow2 = pn2.pow(2);
+    for pn4 in pn.iter() {
+        let pow4 = pn4.pow(4);
+        if pow4 >= LIMIT {
+            break;
+        }
 
         for pn3 in pn.iter() {
-            let sum = pow2 + pn3.pow(3);
+            let sum = pow4 + pn3.pow(3);
             if sum >= LIMIT {
                 break;
             }
 
-            for pn4 in pn.iter() {
-                let sum2 = sum + pn4.pow(4);
+            for pn2 in pn.iter() {
+                let sum2 = sum + pn2.pow(2);
                 if sum2 >= LIMIT {
                     break;
                 }