Output s rather than s^2

4 files changed, 39 insertions, 5 deletions

diff --git a/include/usr/math.h b/include/usr/math.h
new file mode 100644
index 0000000..d3f9591
--- /dev/null
+++ b/include/usr/math.h
@@ -0,0 +1,6 @@
+#ifndef USR_MATH_H
+#define USR_MATH_H
+
+unsigned long sqrt_rnd(unsigned long square);
+
+#endif
diff --git a/usr/math.c b/usr/math.c
new file mode 100644
index 0000000..4d50487
--- /dev/null
+++ b/usr/math.c
@@ -0,0 +1,25 @@
+unsigned long sqrt_rnd(unsigned long square)
+{
+	unsigned long op = square;
+	unsigned long res = 0;
+	unsigned long one = 1uL << 30;
+
+	while (one > op)
+		one >>= 2;
+
+	while (one != 0)
+	{
+		if (op >= res + one)
+		{
+			op = op - (res + one);
+			res = res + 2 * one;
+		}
+		res >>= 1;
+		one >>= 2;
+	}
+
+	if (one > res)
+		res++;
+
+	return res;
+}
diff --git a/usr/string.c b/usr/string.c
index 8c94900..6129d38 100644
--- a/usr/string.c
+++ b/usr/string.c
@@ -10,7 +10,7 @@ char* ulong_to_string(unsigned long value, char* data)
 		if (t==0)
 			break;
 		dptr -= 1;
-		if (i == 5) {
+		if (i == 2) {
 			*dptr = '.';
 			dptr -= 1;
 		}
diff --git a/usr/test.c b/usr/test.c
index 6210384..6ba3a92 100644
--- a/usr/test.c
+++ b/usr/test.c
@@ -1,6 +1,7 @@
 #include <cpu.h>
 #include <graphics/lfb.h>
 #include <sys/schedule.h>
+#include <usr/math.h>
 #include <usr/string.h>
 #include <util/mutex.h>
 
@@ -11,6 +12,7 @@ static unsigned long ti, tf;
 static unsigned long times[MAX_ITER];
 static unsigned long idx = 0;
 
+
 void test_results(unsigned long off)
 {
 	unsigned long mean=0, stdev=0, max=0;
@@ -24,14 +26,15 @@ void test_results(unsigned long off)
 		unsigned long term = (times[i]-mean)*(times[i]-mean)/MAX_ITER;
 		stdev += term;
 	}
-	static char str[13];
+	stdev = sqrt_rnd(stdev);
+	char str[] = "            ns\0";
 	char* start;
 	start = ulong_to_string(mean, str);
-	draw_string(off*13, 12, start);
+	draw_string(off*15, 12, start);
 	start = ulong_to_string(stdev, str);
-	draw_string(off*13, 13, start);
+	draw_string(off*15, 13, start);
 	start = ulong_to_string(max, str);
-	draw_string(off*13, 14, start);
+	draw_string(off*15, 14, start);
 }
 
 void nopfxn(void) {}