From 47aaae2c42d554963fb811b68fdf28c9743598e8 Mon Sep 17 00:00:00 2001
From: Stefan Zabka <zabkaste@hu-berlin.de>
Date: Wed, 10 Jun 2020 17:10:02 +0200
Subject: Starting threadpool

---
 04_exercise/quicksort.c | 119 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 119 insertions(+)
 create mode 100644 04_exercise/quicksort.c

(limited to '04_exercise/quicksort.c')

diff --git a/04_exercise/quicksort.c b/04_exercise/quicksort.c
new file mode 100644
index 0000000..88a47a2
--- /dev/null
+++ b/04_exercise/quicksort.c
@@ -0,0 +1,119 @@
+#include "threadpool.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+static size_t partition(int v[], size_t len);
+
+/* TODO: quicksort-Implementation parallelisieren */
+
+static void quicksort(int list[], size_t len) {
+	if (len <= 1) return;
+	
+	size_t mid = partition(list, len);
+	quicksort(list, mid);
+	quicksort(list + mid + 1, len - mid - 1);
+}
+
+size_t partition(int v[], size_t len) {
+	size_t pivot = len - 1;
+	size_t l = 0, r = len - 2;
+	int t;
+	
+	while (1) {
+		while (l < r && v[l] <  v[pivot]) ++l;
+		while (l < r && v[r] >= v[pivot]) --r;
+		
+		if (l >= r) break;
+		
+		t = v[l];
+		v[l] = v[r];
+		v[r] = t;
+	}
+	
+	if (v[l] >= v[pivot]) {
+		t = v[l];
+		v[l] = v[pivot];
+		v[pivot] = t;
+		return l;
+	}
+	
+	return pivot;
+}
+
+static void list_randomize(int list[], size_t len) {
+	for (int *p = list, *e = p + len; p < e; ++p)
+		*p = ((((double) rand()) / RAND_MAX) - 0.5) * len;
+}
+
+static void list_print(int list[], size_t len) {
+	const char *sep = "";
+	
+	fputs("(", stdout);
+	for (int *p = list, *e = p + len; p < e; ++p, sep = ", ")
+		printf("%s%i", sep, *p);
+	fputs(")\n", stdout);
+}
+
+static int list_is_sorted(int list[], size_t len) {
+	for (int *p = list, *e = p + len - 1; p < e; ++p) {
+		if (p[0] > p[1])
+			return 0;
+	}
+	
+	return 1;
+}
+
+static struct timespec time_diff(struct timespec t1, struct timespec t2) {
+	struct timespec result = {
+		.tv_sec  = t2.tv_sec - t1.tv_sec,
+		.tv_nsec = t2.tv_nsec - t1.tv_nsec
+	};
+	
+	if (t2.tv_nsec - t1.tv_nsec < 0) {
+		result.tv_sec  = t2.tv_sec - t1.tv_sec - 1;
+		result.tv_nsec = 1000000000l + t2.tv_nsec - t1.tv_nsec;
+	}
+	
+	return result;
+}
+
+int main(int argc, const char *argv[]) {
+	if (tpInit(8) != 0)
+		perror("Thread Pool initialization failed"), exit(-1);
+	atexit(&tpRelease);
+	
+	/* read the length of the list from the command line */
+	size_t list_len = 30000000;
+	if (argc >= 2) {
+		long arg = atol(argv[1]);
+		if (arg > 0)
+			list_len = arg;
+	}
+	
+	/* generate a list with random integers */
+	int *list = malloc(sizeof(int) * list_len);
+	list_randomize(list, list_len);
+	printf("Len: %lu\n", list_len);
+	
+	/* print the unsorted list if it's not too long */
+	printf("---- Unsortiert: %i ----\n", list_is_sorted(list, list_len));
+	
+	if (list_len <= 100)
+		list_print(list, list_len);
+	
+	/* sort it and print the sorted list if it's not too long */
+	struct timespec start, end, dt;
+	clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &start);
+	quicksort(list, list_len);
+	clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &end);
+	dt = time_diff(start, end);
+	printf("---- Sortiert:   %i ----\n", list_is_sorted(list, list_len));
+	
+	if (list_len <= 100)
+		list_print(list, list_len);
+	
+	printf("Dauer: %lis %lins\n", dt.tv_sec, dt.tv_nsec);
+	return 0;
+}
-- 
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