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digitalmars.D.learn - "Rolling Hash computation" or "Content Defined Chunking"

reply notna <notna.remove.this ist-einmalig.de> writes:
Hi Dlander's.

Found some interesting reads ([1] [2] [3]) about the $SUBJECT and 
wonder if there is anything available in the Dland?!

If yes, pls. share.
If not, how could it be done (D'ish)

[1] - 
https://moinakg.wordpress.com/2013/06/22/high-performance-content-defined-chunking/
     - 
https://github.com/moinakg/pcompress/blob/master/rabin/rabin_dedup.c

[2] - 
https://restic.github.io/blog/2015-09-12/restic-foundation1-cdc

[3] - http://www.infoarena.ro/blog/rolling-hash

Thanks & regards
May 01
parent reply Johannes Pfau <nospam example.com> writes:
Am Mon, 01 May 2017 21:01:43 +0000
schrieb notna <notna.remove.this ist-einmalig.de>:

 Hi Dlander's.
 
 Found some interesting reads ([1] [2] [3]) about the $SUBJECT and 
 wonder if there is anything available in the Dland?!
 
 If yes, pls. share.
 If not, how could it be done (D'ish)
 
 [1] - 
 https://moinakg.wordpress.com/2013/06/22/high-performance-content-defined-chunking/
      - 
 https://github.com/moinakg/pcompress/blob/master/rabin/rabin_dedup.c
 
 [2] - 
 https://restic.github.io/blog/2015-09-12/restic-foundation1-cdc
 
 [3] - http://www.infoarena.ro/blog/rolling-hash
 
 Thanks & regards
Interesting concept. I'm not aware of any D implementation but it shouldn't be difficult to implement this in D: https://en.wikipedia.org/wiki/Rolling_hash#Cyclic_polynomial There's a BSD licensed haskell implementation, so a BSD licensed port would be very easy to implement: https://hackage.haskell.org/package/optimal-blocks-0.1.0 https://hackage.haskell.org/package/optimal-blocks-0.1.0/docs/src/Algorithm-OptimalBlocks-BuzzHash.html To make an implementation D'ish it could integrate with either std.digest or process input ranges. If you want to use it exclusively for chunking your code can be more efficient (process InputRange until a boundary condition is met). When using input ranges, prefer some kind of buffered approach, Range!ubyte[] instead of Range!ubyte for better performance. If you really want the rolling hash value for each byte in a sequence this will be less efficient as you'll have to enter data byte-by-byte. In this case it's extremely important for performance that your function can be inlined, so use templates: ubyte[] data; foreach(b; data) { // This needs to be inlined for performance reasons rollinghash.put(b); } -- Johannes
May 06
parent reply notna <notna.remove.this ist-einmalig.de> writes:
On Saturday, 6 May 2017 at 07:21:51 UTC, Johannes Pfau wrote:
 Am Mon, 01 May 2017 21:01:43 +0000
 schrieb notna <notna.remove.this ist-einmalig.de>:

 Hi Dlander's.
 
 Found some interesting reads ([1] [2] [3]) about the $SUBJECT 
 and wonder if there is anything available in the Dland?!
 
 If yes, pls. share.
 If not, how could it be done (D'ish)
 
 [1] -
 https://moinakg.wordpress.com/2013/06/22/high-performance-content-defined-chunking/
      -
 https://github.com/moinakg/pcompress/blob/master/rabin/rabin_dedup.c
 
 [2] - 
 https://restic.github.io/blog/2015-09-12/restic-foundation1-cdc
 
 [3] - http://www.infoarena.ro/blog/rolling-hash
 
 Thanks & regards
Interesting concept. I'm not aware of any D implementation but it shouldn't be difficult to implement this in D: https://en.wikipedia.org/wiki/Rolling_hash#Cyclic_polynomial There's a BSD licensed haskell implementation, so a BSD licensed port would be very easy to implement: https://hackage.haskell.org/package/optimal-blocks-0.1.0 https://hackage.haskell.org/package/optimal-blocks-0.1.0/docs/src/Algorithm-OptimalBlocks-BuzzHash.html To make an implementation D'ish it could integrate with either std.digest or process input ranges. If you want to use it exclusively for chunking your code can be more efficient (process InputRange until a boundary condition is met). When using input ranges, prefer some kind of buffered approach, Range!ubyte[] instead of Range!ubyte for better performance. If you really want the rolling hash value for each byte in a sequence this will be less efficient as you'll have to enter data byte-by-byte. In this case it's extremely important for performance that your function can be inlined, so use templates: ubyte[] data; foreach(b; data) { // This needs to be inlined for performance reasons rollinghash.put(b); } -- Johannes
Thanks for the feedback, Johannes. I hoped there may already be something in Mir or Weka.io or somewhere else... Will read the Golang, C and C++ source and see if my Dlang is good enough for ranges and the like magic...
May 09
parent 9il <ilyayaroshenko gmail.com> writes:
On Tuesday, 9 May 2017 at 18:17:45 UTC, notna wrote:
 I hoped there may already be something in Mir or Weka.io or 
 somewhere else... Will read the Golang, C and C++ source and 
 see if my Dlang is good enough for ranges and the like magic...
Hello notha, You may want to open a PR to mir-algorithm. I will help to make code idiomatic. https://github.com/libmir/mir-algorithm Thanks, Ilya
May 09