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From: Peter Tschipper <peter.tschipper@gmail.com>
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Subject: Re: [bitcoin-dev] request BIP number for: "Support for Datastream
 Compression"
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Here are the latest results on compression ratios for the first 295,000
blocks, compressionlevel=6.  I think there are more than enough
datapoints for statistical significance. 

Results are very much similar to the previous test.   I'll work on
getting a comparison between how much time savings/loss in time there is
when syncing the blockchains: compressed vs uncompressed.  Still, I
think it's clear that serving up compressed blocks, at least historical
blocks, will be of benefit for those that have bandwidth caps on their
internet connections.

The proposal, so far is fairly simple:
1) compress blocks with some compression library: currently zlib but I
can investigate other possiblities
2) As a fall back we need to advertise compression as a service.  That
way we can turn off compression AND decompression completely if needed.
3) Do the compression at the datastream level in the code.  CDataStream
is the obvious place.


Test Results:

range = block size range
ubytes = average size of uncompressed blocks
cbytes = average size of compressed blocks
ctime = average time to compress
dtime = average time to decompress
cmp_ratio% = compression ratio
datapoints = number of datapoints taken

range       ubytes    cbytes    ctime    dtime    cmp_ratio%    datapoints
0-250b      215            189    0.001    0.000    12.40             91280
250-500b    438            404    0.001    0.000    7.85             13217
500-1KB     761            701    0.001    0.000    7.86               11434
1KB-10KB    4149    3547    0.001    0.000      14.51             52180
10KB-100KB  41934    32604    0.005    0.001    22.25         82890
100KB-200KB 146303    108080    0.016    0.001    26.13    29886
200KB-300KB 243299    179281    0.025    0.002    26.31    25066
300KB-400KB 344636    266177    0.036    0.003    22.77    4956
400KB-500KB 463201    356862    0.046    0.004    22.96    3167
500KB-600KB 545123    429854    0.056    0.005    21.15    366
600KB-700KB 647736    510931    0.065    0.006    21.12    254
700KB-800KB 746540    587287    0.073    0.008    21.33    294
800KB-900KB 868121    682650    0.087    0.008    21.36    199
900KB-1MB   945747    726307    0.091    0.010    23.20    304

On 10/11/2015 8:46 AM, Jeff Garzik via bitcoin-dev wrote:
> Comments:
>
> 1) cblock seems a reasonable way to extend the protocol.  Further
> wrapping should probably be done at the stream level.
>
> 2) zlib has crappy security track record.
>
> 3) A fallback path to non-compressed is required, should compression
> fail or crash.
>
> 4) Most blocks and transactions have runs of zeroes and/or highly
> common bit-patterns, which contributes to useful compression even at
> smaller sizes.  Peter Ts's most recent numbers bear this out.  zlib
> has a dictionary (32K?) which works well with repeated patterns such
> as those you see with concatenated runs of transactions.
>
> 5) LZO should provide much better compression, at a cost of CPU
> performance and using a less-reviewed, less-field-tested library.
>
>
>
>
>
> On Tue, Nov 10, 2015 at 11:30 AM, Tier Nolan via bitcoin-dev
> <bitcoin-dev@lists.linuxfoundation.org
> <mailto:bitcoin-dev@lists.linuxfoundation.org>> wrote:
>
>
>
>     On Tue, Nov 10, 2015 at 4:11 PM, Peter Tschipper
>     <peter.tschipper@gmail.com <mailto:peter.tschipper@gmail.com>> wrote:
>
>         There are better ways of sending new blocks, that's certainly
>         true but for sending historical blocks and seding transactions
>         I don't think so.  This PR is really designed to save
>         bandwidth and not intended to be a huge performance
>         improvement in terms of time spent sending.
>
>
>     If the main point is for historical data, then sticking to just
>     blocks is the best plan.
>
>     Since small blocks don't compress well, you could define a
>     "cblocks" message that handles multiple blocks (just concatenate
>     the block messages as payload before compression). 
>
>     The sending peer could combine blocks so that each cblock is
>     compressing at least 10kB of block data (or whatever is optimal). 
>     It is probably worth specifying a maximum size for network buffer
>     reasons (either 1MB or 1 block maximum).
>
>     Similarly, transactions could be combined together and compressed
>     "ctxs".  The inv messages could be modified so that you can
>     request groups of 10-20 transactions.  That would depend on how
>     much of an improvement compressed transactions would represent.
>
>     More generally, you could define a message which is a compressed
>     message holder.  That is probably to complex to be worth the
>     effort though.
>
>      
>
>>
>>         On Tue, Nov 10, 2015 at 5:40 AM, Johnathan Corgan via
>>         bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org
>>         <mailto:bitcoin-dev@lists.linuxfoundation.org>> wrote:
>>
>>             On Mon, Nov 9, 2015 at 5:58 PM, gladoscc via bitcoin-dev
>>             <bitcoin-dev@lists.linuxfoundation.org
>>             <mailto:bitcoin-dev@lists.linuxfoundation.org>> wrote:
>>              
>>
>>                 I think 25% bandwidth savings is certainly
>>                 considerable, especially for people running full
>>                 nodes in countries like Australia where internet
>>                 bandwidth is lower and there are data caps.
>>
>>
>>             ​ This reinforces the idea that such trade-off decisions
>>             should be be local and negotiated between peers, not a
>>             required feature of the network P2P.​
>>              
>>
>>             -- 
>>             Johnathan Corgan
>>             Corgan Labs - SDR Training and Development Services
>>             http://corganlabs.com
>>
>>             _______________________________________________
>>             bitcoin-dev mailing list
>>             bitcoin-dev@lists.linuxfoundation.org
>>             <mailto:bitcoin-dev@lists.linuxfoundation.org>
>>             https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>>
>>
>>
>>
>>         _______________________________________________
>>         bitcoin-dev mailing list
>>         bitcoin-dev@lists.linuxfoundation.org
>>         <mailto:bitcoin-dev@lists.linuxfoundation.org>
>>         https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>
>
>
>     _______________________________________________
>     bitcoin-dev mailing list
>     bitcoin-dev@lists.linuxfoundation.org
>     <mailto:bitcoin-dev@lists.linuxfoundation.org>
>     https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>
>
>
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev@lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev


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    <div class="moz-cite-prefix">Here are the latest results on
      compression ratios for the first 295,000 blocks,
      compressionlevel=6.  I think there are more than enough datapoints
      for statistical significance.  <br>
      <br>
      Results are very much similar to the previous test.   I'll work on
      getting a comparison between how much time savings/loss in time
      there is when syncing the blockchains: compressed vs
      uncompressed.  Still, I think it's clear that serving up
      compressed blocks, at least historical blocks, will be of benefit
      for those that have bandwidth caps on their internet connections.<br>
      <br>
      The proposal, so far is fairly simple:<br>
      1) compress blocks with some compression library: currently zlib
      but I can investigate other possiblities<br>
      2) As a fall back we need to advertise compression as a service. 
      That way we can turn off compression AND decompression completely
      if needed.<br>
      3) Do the compression at the datastream level in the code. 
      CDataStream is the obvious place.<br>
      <br>
      <br>
      Test Results:<br>
      <br>
      range = block size range<br>
      ubytes = average size of uncompressed blocks<br>
      cbytes = average size of compressed blocks<br>
      ctime = average time to compress<br>
      dtime = average time to decompress<br>
      cmp_ratio% = compression ratio<br>
      datapoints = number of datapoints taken<br>
      <br>
      range       ubytes    cbytes    ctime    dtime    cmp_ratio%   
      datapoints<br>
      0-250b      215            189    0.001    0.000    12.40        
          91280<br>
      250-500b    438            404    0.001    0.000    7.85          
        13217<br>
      500-1KB     761            701    0.001    0.000   
      7.86               11434<br>
      1KB-10KB    4149    3547    0.001    0.000      14.51            
      52180<br>
      10KB-100KB  41934    32604    0.005    0.001    22.25        
      82890<br>
      100KB-200KB 146303    108080    0.016    0.001    26.13    29886<br>
      200KB-300KB 243299    179281    0.025    0.002    26.31    25066<br>
      300KB-400KB 344636    266177    0.036    0.003    22.77    4956<br>
      400KB-500KB 463201    356862    0.046    0.004    22.96    3167<br>
      500KB-600KB 545123    429854    0.056    0.005    21.15    366<br>
      600KB-700KB 647736    510931    0.065    0.006    21.12    254<br>
      700KB-800KB 746540    587287    0.073    0.008    21.33    294<br>
      800KB-900KB 868121    682650    0.087    0.008    21.36    199<br>
      900KB-1MB   945747    726307    0.091    0.010    23.20    304<br>
      <br>
      On 10/11/2015 8:46 AM, Jeff Garzik via bitcoin-dev wrote:<br>
    </div>
    <blockquote
cite="mid:CADm_WcYAj9_r6tu8Be-U81LDwWvnv04PZJMmc-S4cY7+jxfzGw@mail.gmail.com"
      type="cite">
      <div dir="ltr">Comments:
        <div><br>
        </div>
        <div>1) cblock seems a reasonable way to extend the protocol. 
          Further wrapping should probably be done at the stream level.</div>
        <div><br>
        </div>
        <div>2) zlib has crappy security track record.</div>
        <div><br>
        </div>
        <div>3) A fallback path to non-compressed is required, should
          compression fail or crash.</div>
        <div><br>
        </div>
        <div>4) Most blocks and transactions have runs of zeroes and/or
          highly common bit-patterns, which contributes to useful
          compression even at smaller sizes.  Peter Ts's most recent
          numbers bear this out.  zlib has a dictionary (32K?) which
          works well with repeated patterns such as those you see with
          concatenated runs of transactions.</div>
        <div><br>
        </div>
        <div>5) LZO should provide much better compression, at a cost of
          CPU performance and using a less-reviewed, less-field-tested
          library.</div>
        <div><br>
        </div>
        <div><br>
        </div>
        <div><br>
        </div>
        <div><br>
        </div>
      </div>
      <div class="gmail_extra"><br>
        <div class="gmail_quote">On Tue, Nov 10, 2015 at 11:30 AM, Tier
          Nolan via bitcoin-dev <span dir="ltr">&lt;<a
              moz-do-not-send="true"
              href="mailto:bitcoin-dev@lists.linuxfoundation.org"
              target="_blank"><a class="moz-txt-link-abbreviated" href="mailto:bitcoin-dev@lists.linuxfoundation.org">bitcoin-dev@lists.linuxfoundation.org</a></a>&gt;</span>
          wrote:<br>
          <blockquote class="gmail_quote" style="margin:0 0 0
            .8ex;border-left:1px #ccc solid;padding-left:1ex">
            <div dir="ltr"><br>
              <div class="gmail_extra"><br>
                <div class="gmail_quote"><span class="">On Tue, Nov 10,
                    2015 at 4:11 PM, Peter Tschipper <span dir="ltr">&lt;<a
                        moz-do-not-send="true"
                        href="mailto:peter.tschipper@gmail.com"
                        target="_blank"><a class="moz-txt-link-abbreviated" href="mailto:peter.tschipper@gmail.com">peter.tschipper@gmail.com</a></a>&gt;</span>
                    wrote:<br>
                    <blockquote class="gmail_quote" style="margin:0 0 0
                      .8ex;border-left:1px #ccc solid;padding-left:1ex">
                      <span></span><span></span>There are better ways of
                      sending new blocks, that's certainly true but for
                      sending historical blocks and seding transactions
                      I don't think so.  This PR is really designed to
                      save bandwidth and not intended to be a huge
                      performance improvement in terms of time spent
                      sending.<span><br>
                      </span></blockquote>
                    <div><br>
                    </div>
                  </span>
                  <div>If the main point is for historical data, then
                    sticking to just blocks is the best plan.<br>
                    <br>
                  </div>
                  <div>Since small blocks don't compress well, you could
                    define a "cblocks" message that handles multiple
                    blocks (just concatenate the block messages as
                    payload before compression).  <br>
                    <br>
                    The sending peer could combine blocks so that each
                    cblock is compressing at least 10kB of block data
                    (or whatever is optimal).  It is probably worth
                    specifying a maximum size for network buffer reasons
                    (either 1MB or 1 block maximum).<br>
                    <br>
                  </div>
                  <div>Similarly, transactions could be combined
                    together and compressed "ctxs".  The inv messages
                    could be modified so that you can request groups of
                    10-20 transactions.  That would depend on how much
                    of an improvement compressed transactions would
                    represent. <br>
                    <br>
                  </div>
                  <div>More generally, you could define a message which
                    is a compressed message holder.  That is probably to
                    complex to be worth the effort though.<br>
                  </div>
                  <span class="">
                    <div><br>
                       </div>
                    <blockquote class="gmail_quote" style="margin:0 0 0
                      .8ex;border-left:1px #ccc solid;padding-left:1ex">
                      <div bgcolor="#FFFFFF" text="#000000"><span>
                          <blockquote type="cite">
                            <div class="gmail_extra"><br>
                              <div class="gmail_quote">On Tue, Nov 10,
                                2015 at 5:40 AM, Johnathan Corgan via
                                bitcoin-dev <span dir="ltr">&lt;<a
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                                wrote:<br>
                                <blockquote class="gmail_quote"
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                                  <div dir="ltr"><span>
                                      <div style="font-size:small">On
                                        Mon, Nov 9, 2015 at 5:58 PM,
                                        gladoscc via bitcoin-dev <span
                                          dir="ltr">&lt;<a
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                                            href="mailto:bitcoin-dev@lists.linuxfoundation.org"
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                                        wrote:<br>
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                                          <div> </div>
                                          <blockquote
                                            class="gmail_quote"
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                                            <div dir="ltr">I think 25%
                                              bandwidth savings is
                                              certainly considerable,
                                              especially for people
                                              running full nodes in
                                              countries like Australia
                                              where internet bandwidth
                                              is lower and there are
                                              data caps.</div>
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                                          <div
                                            style="font-size:small;display:inline">​
                                            This reinforces the idea
                                            that such trade-off
                                            decisions should be be local
                                            and negotiated between
                                            peers, not a required
                                            feature of the network P2P.​</div>
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                                        -- <br>
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                                                      <div dir="ltr">
                                                        <div>Johnathan
                                                          Corgan<br>
                                                          Corgan Labs -
                                                          SDR Training
                                                          and
                                                          Development
                                                          Services</div>
                                                        <div><a
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href="http://corganlabs.com" style="font-size:12.8px" target="_blank"><a class="moz-txt-link-freetext" href="http://corganlabs.com">http://corganlabs.com</a></a><br>
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