[rrd-users] Using PRINT to output a MAX value for very short period

Alex van den Bogaerdt alex at vandenbogaerdt.nl
Thu Apr 4 00:15:58 CEST 2013

> Sometimes with step=300 or 320 and 1 minute between start and end, I get 
> an error like this:
> SANITY CHECK: 18446744073709551611 rows cannot be reduced by 5
> BUG in reduce_data()
> I feel like I am misunderstanding something basic here.  Can anyone 
> explain what I am seeing?
> RRDtool 1.4.7

This was programmed eons ago; it could also have read "This should never 
happen, what's going on?"

AFAIK you are the first to report this.

Given the extremely large number, I suspect there's a problem with 64-bit 
18446744073709551611  is 0xFFFFFFFFFFFFFFFB is -5.

I'm almost sure it has to do with start and end times not being exactly what 
they should be (and I'm talking about RRDtool here, not what you provide as 

I'm sorry, I cannot debug this right now, but hopefully someone else can 
pick this up.


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