<div dir="ltr"><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Apr 7, 2014 at 8:50 PM, Tamas Blummer <span dir="ltr"><<a href="mailto:tamas@bitsofproof.com" target="_blank">tamas@bitsofproof.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="word-wrap:break-word">You have to load headers sequantially to be able to connect them and determine the longest chain.</div>
</blockquote><div><br></div><div style="word-wrap:break-word">The isn't strictly true. If you are connected to a some honest nodes, then you could download portions of the chain and then connect the various sub-chains together.<br>
<br>The protocol doesn't support it though. There is no system to ask for block headers for the main chain block with a given height,<br><br></div>Finding one high bandwidth peer to download the entire header chain sequentially is pretty much forced. The client can switch if there is a timeout.<br>
<br></div><div class="gmail_quote">Other peers could be used to parallel download the block chain while the main chain is downloading. Even if the header download stalled, it wouldn't be that big a deal.<br></div><div class="gmail_quote">
<div style="word-wrap:break-word"><br><div><div>> Blocks can be loaded in random order once you have their order given by the headers.</div>> Computing the UTXO however will force you to at least temporarily store the blocks unless you have plenty of RAM. <br>
<br></div><div>You only need to store the UTXO set, rather than the entire block chain.<br><br></div><div>It is possible to generate the UTXO set without doing any signature verification.<br><br></div><div>A lightweight node could just verify the UTXO set and then do random signature verifications.<br>
<br></div><div>The keeps disk space and CPU reasonably low. If an illegal transaction is added to be a block, then proof could be provided for the bad transaction.<br><br></div><div>The only slightly difficult thing is confirming inflation. That can be checked on a block by block basis when downloading the entire block chain.<br>
</div><div><br style="text-indent:0px;letter-spacing:normal;font-variant:normal;font-style:normal;font-weight:normal;line-height:normal;text-transform:none;font-size:12px;white-space:normal;font-family:Helvetica;word-spacing:0px">
<div><span style="text-indent:0px;letter-spacing:normal;font-variant:normal;font-style:normal;display:inline!important;font-weight:normal;float:none;line-height:normal;text-transform:none;font-size:12px;white-space:normal;font-family:Helvetica;word-spacing:0px">> Regards,</span><br style="text-indent:0px;letter-spacing:normal;font-variant:normal;font-style:normal;font-weight:normal;line-height:normal;text-transform:none;font-size:12px;white-space:normal;font-family:Helvetica;word-spacing:0px">
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</span></div>
<br><div><div class=""><div>On 07.04.2014, at 21:30, Paul Lyon <<a href="mailto:pmlyon@hotmail.ca" target="_blank">pmlyon@hotmail.ca</a>> wrote:</div><br></div><blockquote type="cite"><div style="font-size:12pt;font-family:Calibri;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
<div dir="ltr"><div class="">I hope I'm not thread-jacking here, apologies if so, but that's the approach I've taken with the node I'm working on.<div><br></div><div>Headers can be downloaded and stored in any order, it'll make sense of what the winning chain is. Blocks don't need to be downloaded in any particular order and they don't need to be saved to disk, the UTXO is fully self-contained. That way the concern of storing blocks for seeding (or not) is wholly separated from syncing the UTXO. This allows me to do the initial blockchain sync in ~6 hours when I use my SSD. I only need enough disk space to store the UTXO, and then whatever amount of block data the user would want to store for the health of the network.</div>
<div><br></div></div><div><div class="">This project is a bitcoin learning exercise for me, so I can only hope I don't have any critical design flaws in there. :)<br><br></div><div><div class=""><hr>From:<span> </span><a href="mailto:tamas@bitsofproof.com" target="_blank">tamas@bitsofproof.com</a><br>
Date: Mon, 7 Apr 2014 21:20:31 +0200<br>To:<span> </span><a href="mailto:gmaxwell@gmail.com" target="_blank">gmaxwell@gmail.com</a><br>CC:<span> </span><a href="mailto:bitcoin-development@lists.sourceforge.net" target="_blank">bitcoin-development@lists.sourceforge.net</a><br>
Subject: Re: [Bitcoin-development] Why are we bleeding nodes?<br><br><div><br></div><div>Once headers are loaded first there is no reason for sequential loading. </div><div><br></div><div>Validation has to be sequantial, but that step can be deferred until the blocks before a point are loaded and continous.</div>
<br><div><span style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;float:none;display:inline!important">Tamas Blummer</span><span style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px"><br style="font-family:Helvetica;font-size:12px;font-style:normal;font-variant:normal;font-weight:normal;letter-spacing:normal;line-height:normal;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px">
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<br><div><div>On 07.04.2014, at 21:03, Gregory Maxwell <<a href="mailto:gmaxwell@gmail.com" target="_blank">gmaxwell@gmail.com</a>> wrote:</div><br><blockquote type="cite">On Mon, Apr 7, 2014 at 12:00 PM, Tamas Blummer <<a href="mailto:tamas@bitsofproof.com" target="_blank">tamas@bitsofproof.com</a>> wrote:<br>
<blockquote type="cite">therefore I guess it is more handy to return some bitmap of pruned/full<br>blocks than ranges.<br></blockquote><br>A bitmap also means high overhead and— if it's used to advertise<br>non-contiguous blocks— poor locality, since blocks are fetched<br>
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