[rrd-users] Re: cdef + rpn

[steve rader]

 > From: "Neil Calvert"
 > I have a problem converting a calculation to RPN and perhaps someone can
 > help.
 > 
 > The calculation I have to do is of the form :
 > 
 > ( ( <octets per second> * 8 ) / <bandwidth in bits> ) * 100
 > 
 > to return a percentage of bandwidth used.
 > 
 > The two forms I've tried with CDEF are :
 > 
 > o,8,*,b,/,100,*

This looks right:

 o,8,*  			--> output_in_bits

 output_in_bits,b,/ 		--> bandwidth_fraction 

 bandwidth_fraction,100,*  	--> percent bandwidth

I verifed with a graph of a T1 circuit:

 [...]
 CDEF:in_bits=input,8,*
 CDEF:in_per2=input,8,*,1536000,/,100,*
 [...]
 GPRINT:in_bits:LAST:"%6.2lf last bits" 
 GPRINT:in_per2:LAST:"%6.2lf %% used last\n"

For example: when last is 352685... I get a graph
labels like

 "352685.nn last bits 22.96 % used last"

and

  352685/1536000*100 = 22.96 %

and the, ah, what?, converse is...

  22.96/100*1536000 = 352665

Lastly, the scaled last output is 352 kbits/sec and

  352 kbits / 1536 kbits = 22.91%

later
steve
- - -
systems guy
wiscnet.net

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