Check_Item Is Always Equal To 0 When 2^32

[Matthew Newton]

On Thu, Oct 24, 2013 at 11:35:30AM +0000, Russell Mike wrote:
> >   I can't make it any clearer than that.
> 
> thank you very very much, it is great explanation. Your response made
> many things very clearer. But did not work for me still. Perhaps my formula
> is wrong. Kindly help one more step further. Honestly, i have tried very
> hard, working on it for some weeks now without results. i.e. i want to set
> 6GB limit.
> 
> total bytes in 6GB = 805306368
> total bytes in 4GB = 536870912

Not sure where you got these from.

6GB = 6 * 1024 * 1024 * 1024 = 4 * 1024^3 = 6442450944

6GB in binary is

0000000000000000000000000000000110000000000000000000000000000000

3210987654321098765432109876543210987654321098765432109876543210
   6         5         4         3         2         1         0

So the lower 32 bits are:

10000000000000000000000000000000

and the upper 32 bits are:

00000000000000000000000000000001

The lower bits can be found by bitwise AND with (2^32)-1 (i.e. 32
ones):

$ python
>>> 6*(1024**3) & ((2**32)-1)
2147483648

The upper 32 bits by shifting right by 32 bits:

>>> 6*(1024**3) >> 32
1


So you want 

> i put 536870912 in ChilliSpot-Max-Input-Octets

this should be 2147483648;

> i put 268435456 in ChilliSpot-Max-Input-Gigawords

This should be 1.

To confirm the numbers are correct, left-shift the gigawords by 32
bits, then add the octets. Should come back to the original value:

>>> (1<<32) + 2147483648
6442450944
>>> 6*(1024**3)
6442450944

Matthew


-- 
Matthew Newton, Ph.D. <mcn4 at le.ac.uk>

Systems Specialist, Infrastructure Services,
I.T. Services, University of Leicester, Leicester LE1 7RH, United Kingdom

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