diff mbox

batctl: Correct mdev calculation in ping subcommand

Message ID 4BF55C08.7010704@tiwoc.de
State Superseded, archived
Headers show

Commit Message

Daniel Seither May 20, 2010, 3:58 p.m. UTC
Fixes the calculation of the mean absolute deviation (mdev)
of the roundtrip times. mdev was previously calculated by
computing the difference of maximum and minimum round trip times.

The calculation is now done using the same formula as in the iputils
ping program.

Signed-off-by: Daniel Seither <post@tiwoc.de>
---

Comments

Daniel Seither May 20, 2010, 4:10 p.m. UTC | #1
Sorry, I sent the wrong version of the patch. I'll send a fixed patch in
a minute...

- Daniel

Am 20.05.2010 17:58, schrieb Daniel Seither:
> Fixes the calculation of the mean absolute deviation (mdev)
> of the roundtrip times. mdev was previously calculated by
> computing the difference of maximum and minimum round trip times.
> 
> The calculation is now done using the same formula as in the iputils
> ping program.
> 
> Signed-off-by: Daniel Seither <post@tiwoc.de>
> ---
diff mbox

Patch

Index: ping.c
===================================================================
--- ping.c	(revision 1659)
+++ ping.c	(working copy)
@@ -76,7 +76,7 @@ 
 	unsigned int seq_counter = 0, packets_out = 0, packets_in = 0, packets_loss;
 	char *dst_string, *mac_string, *rr_string;
 	double time_delta;
-	float min = 0.0, max = 0.0, avg = 0.0;
+	float min = 0.0, max = 0.0, avg = 0.0, mdev = 0.0;
 	uint8_t last_rr_cur = 0, last_rr[BAT_RR_LEN][ETH_ALEN];
 	size_t packet_len;

@@ -260,6 +260,7 @@ 
 			if (time_delta > max)
 				max = time_delta;
 			avg += time_delta;
+			mdev += time_delta * time_delta;
 			packets_in++;
 			break;
 		case DESTINATION_UNREACHABLE:
@@ -289,11 +290,20 @@ 
 	else
 		packets_loss = ((packets_out - packets_in) * 100) / packets_out;

+	if (packets_in) {
+		avg /= packets_in;
+		mdev /= packets_in;
+		mdev = sqrt(mdev - avg * avg);
+	} else {
+		avg = 0.0;
+		mdev = 0.0;
+	}
+
 	printf("--- %s ping statistics ---\n", dst_string);
 	printf("%u packets transmitted, %u received, %u%% packet loss\n",
 		packets_out, packets_in, packets_loss);
 	printf("rtt min/avg/max/mdev = %.3f/%.3f/%.3f/%.3f ms\n",
-		min, (packets_in ? (avg / packets_in) : 0.000), max, (max - min));
+		min, avg, max, mdev);

 	ret = EXIT_SUCCESS;