Initial commit

OK, I'm late, sue me.

2 files changed, 70 insertions, 0 deletions

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..5ec3953
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,18 @@
+CC = gcc
+CFLAGS = \
+	-Wall -Wmissing-prototypes -Wstrict-prototypes \
+	-D _GNU_SOURCE -O2 -std=gnu11 -ggdb3
+
+BINARY = cpiday
+OBJECTS = main.o
+
+$(BINARY): $(OBJECTS)
+	$(CC) -o $@ $^ -lm
+
+%.o: %.c
+	$(CC) $(CFLAGS) -c -o $@ $<
+
+clean:
+	rm -f $(BINARY) $(OBJECTS)
+
+.PHONY: clean
diff --git a/main.c b/main.c
new file mode 100644
index 0000000..876efc9
--- /dev/null
+++ b/main.c
@@ -0,0 +1,52 @@
+/*
+ * Celebrate Pi day in C.
+ *
+ * See https://www.youtube.com/watch?v=RZBhSi_PwHU to watch Matt Parker
+ * do it the hard way.
+ */
+
+#include <math.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+#define NR_PAIRS 1000000
+
+static unsigned int
+gcd(unsigned int a, unsigned int b)
+{
+    unsigned int tmp;
+
+    while (b != 0) {
+        tmp = b;
+        b = a % b;
+        a = tmp;
+    }
+
+    return a;
+}
+
+static bool
+coprimes(unsigned int a, unsigned int b)
+{
+    return (gcd(a, b) == 1);
+}
+
+int
+main(int argc, char **argv)
+{
+    unsigned int i, total;
+    double pi;
+
+    srand(time(NULL));
+
+    for (i = 0, total = 0; i < NR_PAIRS; i++) {
+        if (coprimes(rand(), rand())) {
+            total++;
+        }
+    }
+
+    pi = sqrt(6. * NR_PAIRS / total);
+    printf("%f\n", pi);
+}