Centos 6/x86-64

what's the type of information for that item ?

Числовой (целое положительное)

I guess
numerical (positive integer)
in english
anyway , if 2 packets from 20
loss than 10 percent
if 1 - then 5 percent

then please set it to float (or whatever is it in the translated version )

why? is 10.0 = 9 ?

hmm, good point. 9 probably shouldn't be there, although float might give better idea about what's happening.

also, which fping version ? usually zabbix should just use result from fping anyway

Hello!

I'll change data type to float and when loss will be here again I'll report about results.

btw,

fping -v
fping: Version 3.4
fping: comments to [email protected]

it is from
Version : 3.4 Vendor: Dag Apt Repository, http://dag.wieers.com/apt/
Release : 1.el6.rf

Thank you!

Well, I can't reproduce this with float, so something is wrong with data types...

The problem is that not all numbers are precisely representable in floating-point. In this case, we calculate ping loss percentage as follows:

value_dbl = 100 * (1 - (double)hosts[h].rcv / (double)hosts[h].cnt);

If rcv=18 and cnt=20, then 18/20 cannot be represented precisely and so value_dbl becomes approximately 9.99999999999999822364, which upon conversion to integer gets truncated to 9.

If we rewrite the calculation to use less floating-point operations, then it works well:

value_dbl = 100 * ((hosts[h].cnt - hosts[h].rcv) / (double)hosts[h].cnt);

For the future, we should make it a guideline to write expressions with as few floating-point operations as possible.

Fixed in development branch svn://svn.zabbix.com/branches/dev/ZBX-5717 .

(1) Take a look at my changes in r52930.

asaveljevs Looks good. CLOSED.

(2) Please take a look at changes in r52935. It changes how the expression is written:

-        value_dbl = 100 * ((host->cnt - host->rcv) / (double)host->cnt);
+        value_dbl = (100 * (host->cnt - host->rcv)) / (double)host->cnt;

A number like 0.1 cannot be represented in floating-point exactly. With "rcv=9" and "cnt=10", the parentheses in the first expression will have 0.1 as an intermediate result.

In the second expression, evaluation will proceed as (100 * (10 - 9)) / 10.0 = (100 * 1) / 10.0 = 100 / 10.0 = 10.0, all of which can be represented in floating-point exactly.

sasha Looks good! CLOSED

(3) Documented the guideline at https://www.zabbix.org/wiki/C_coding_guidelines#Best_practices.

sasha CLOSED

Fixed in pre-2.0.15 r53022, pre-2.2.10 r53023, pre-2.4.5 r53024, pre-2.5.0 (trunk) r53025.