From 8a521dd2782e91ebf9598fdec88950f3f95f3bb7 Mon Sep 17 00:00:00 2001
From: Valentin Gehrke <madmaurice@zom.bi>
Date: Mon, 15 Feb 2016 17:25:46 +0100
Subject: [PATCH] EPA: Bitonic sort

---
 bitonic.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 bitonic.c

diff --git a/bitonic.c b/bitonic.c
new file mode 100644
index 0000000..c9bdf99
--- /dev/null
+++ b/bitonic.c
@@ -0,0 +1,56 @@
+#include <stdio.h>
+#include <assert.h>
+#include <time.h>
+#include <stdlib.h>
+
+#define TESTSIZE ((size_t)( 1<<25 ))
+
+void comp_and_swap(int* data, size_t i, size_t j) {
+    if(data[i] > data[j]) {
+        int tmp = data[i];
+        data[i] = data[j];
+        data[j] = tmp;
+    }
+}
+
+void sort_step(int* data, size_t N, size_t shift, unsigned int step) {
+    for(size_t i = 0; i < N; i+=2*shift) {
+        for(size_t j = i; j < i+shift; j++) {
+            if( (i/step)%2 == 0 ) {
+                comp_and_swap(data, j, j+shift);
+            } else {
+                comp_and_swap(data, j+shift, j);
+            }
+        }
+    }
+}
+
+void sort_step2(int* data, size_t N, size_t step) {
+    for(size_t i = step; i > 1; i/=2) {
+        sort_step(data, N, i/2, step);
+    }
+}
+
+void bitonic_sort(int* data, size_t N) {
+    for(size_t step = 2; step <= N; step*=2) {
+        printf("Pack: %d\n", step);
+        sort_step2(data, N, step);
+    }
+}
+
+int main( int argc, char *argv[] ) {
+    srand(time(NULL));
+
+    int* data = malloc(sizeof(int) * TESTSIZE);
+    for(size_t i = 0; i < TESTSIZE; i++) {
+        data[i] = rand() % 1000;
+    }
+
+    bitonic_sort(data, TESTSIZE);
+
+    for(size_t i = 0; i < TESTSIZE-1; i++) {
+        assert(data[i] <= data[i+1]);
+    }
+
+	return 0;
+}