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The source for notes on this are under doc/, and the pdf version can be found in: http://www.kkourt.io/misc/entropy.pdf.

FILES

  • entropy.c : calculate the entropy of a file
  • entro.py : create a file with a given entropy value
  • pd_mkfile.c : create a file, given the probability distribution
  • graph-entro.py : generate and graph different probability distributions

Compile:

 $ make
 gcc -lm -Wall -Winline -O3 -ffast-math -Wdisabled-optimization -g  -DPD_MKFILE_REPORT_RATE -o entropy entropy.c
 gcc -lm -Wall -Winline -O3 -ffast-math -Wdisabled-optimization -g  -DPD_MKFILE_REPORT_RATE -o pd_mkfile pd_mkfile.c

Create a 12MB file with an entropy of 4.5

$ python2 entro.py 4.5 file-12MB 12582912
4194304 (/12582912) in 0.326706 secs [rate=12.243424]
8388608 (/12582912) in 0.612545 secs [rate=13.060265]
12582912 (/12582912) in 0.892761 secs [rate=13.441447]
$ ./entropy file-12MB 
entropy for file-12MB <0->12582912>: 4.5028

Plot probability distributions generated with an entropy of 6.5

 $ python2 graph-entro.py 6.5 plot-entropy-6.5.png