Skip to content

Commit

Permalink
Browse files Browse the repository at this point in the history
  • Loading branch information
Bulat-Ziganshin committed Feb 9, 2014
2 parents 5f658a9 + 1cb473a commit 3005002
Showing 1 changed file with 5 additions and 5 deletions.
10 changes: 5 additions & 5 deletions README.md
Original file line number Diff line number Diff line change
Expand Up @@ -6,14 +6,14 @@ Datatype detection in order to choose appropriate compression algorithm or not c
Since text, multimedia and incompresible files are better processed with specific algorithms, we need a fast and reliable way to detect those data. I call it data smoking. This project will provide various experimental algorithms that can recognize some of special datatypes (not necessary all), as well as samples of data that are especially hard to smoke correctly.


The full list of smells (speeds measured on the single core of i7-4770) and minimum recommended block sizes to provide meaningful results:
The full list of smokers (with speeds measured on the single core of i7-4770 and minimum recommended block sizes to provide meaningful results):

- Byte entropy: computes entropy of independent bytes (2 GB/s, 16 KBytes)
- Word entropy: computes entropy of independent 16-bit words (0.7-1.5 GB/s, 4 MBytes)
- Order-1 byte entropy: computes order-1 entropy of bytes (0.7-1.5 GB/s, 4 MBytes)
- DWord coverage: computes coverage of independent 32-bit dwords (0.5 GB/s, STEP*FILTER*64 bytes, default STEP=1, FILTER=16).


-
And examples of their work:

Text file (enwik9) | min % | avg % | max % | incompressible 4MB blocks
Expand Down Expand Up @@ -44,7 +44,7 @@ Order-1 byte entropy | 17.69 | 59.81 | 90.39 | 0 of 239
Order-1 byte entropy | 99.85 | 99.86 | 99.86 | 67 of 67
DWord coverage | 99.13 | 99.18 | 99.23 | 67 of 67

-
The whole idea of the library is that we get data of unknown type and analyze them to determine whether it's text, incompressible or so. Overall, I think that ByteEntropy should suffice for 95% of cases, failing only on repetitions of random data (such as two copies of the same zip file) and DWordCoverage should suffice on another 95%, failing on things like base64 encoding (random data of limited charset). I tend to consider as incompressible the data that has >95% for both ByteEntropy and DWordCoverage. Combining them together should provide us with algorithm processing 2 GB/s (since ByteSmoker and DWordSmoker employs different CPU resources) and able to determine almost any data that can be compressed by some algorithm.

The whole idea of the library is that we get data of unknown type and analyze them to determine whether it's text, incompressible or so. Overall, I think that ByteSmoker should suffice for 95% of cases, failing only on repetitions of random data (such as two copies of the same zip file) and DWordSmoker should suffice on another 95%, failing on things like base64 encoding (random data of limited charset). I tend to consider as incompressible the data that has >90% for both ByteSmoker and DWordSmoker. Combining them together should provide us with algorithm processing 2 GB/s (since ByteSmoker and DWordSmoker employs different CPU resources) and able to determine almost any data that can be compressed by some algorithm.

Please provide us with the samples of compressible data having unusually high "entropy" values, especially in ByteSmoker and DWordSmoker simultaneously.
Please provide us with the samples of compressible data having unusually high "entropy" values, especially in ByteEntropy and DWordCoverage simultaneously.

0 comments on commit 3005002

Please sign in to comment.