[rrd-users] Re: Problems with large counters?

Darren Gamble Darren.Gamble at sjrb.ca
Mon Mar 17 17:47:24 MET 2003

Good day,

Sorry for my late reply.  I did not check my messages over the weekend.

> > I grabbed two sample counters- going from 1.1382094242105E+14 to
> > 1.1382517014663E+14 , for example.
> >

> could it be that you are not feeding rrdtool integers but numbers
> which got converted to float in the meantime and then back ?

No, the numbers I pasted there are exactly how they were fed into rrdtool.
Here's the actual command line.

/usr/bin/rrdtool update

.. and then...

/usr/bin/rrdtool update

The change in the first counter (the slightly smaller one) is recorded fine.
The change in the second one is recorded as zero.  I difference between the
two numbers is certainly significant enough that a program should be easily
capable of finding the difference.

The command is generated dynamically with PHP using its default output
format, BTW.

> will cause you to loose precision at the low end, so that at some
> point the difference between two high numbers is becomming zero ...
> rrdtool has arbitrary precision when building the difference of
> two numbers ... there could be bugs in rrdtool too, just guessing
> ...

Perhaps rrdtool itself is doing some sort of conversion that causes it to
lose precision?  Or perhaps it doesn't properly understand the exponent?

Darren Gamble
Planner, Regional Services
Shaw Cablesystems GP
630 - 3rd Avenue SW
Calgary, Alberta, Canada
T2P 4L4
(403) 781-4948

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