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A "Cuckoo Filter" is a nifty data structure invented a few years ago; read the paper for details.

Like a Bloom filter, you insert items and then can later ask "does this item exist in the filter?" You'll get either a definite "no" or "yes, probably" with some false-positive error rate. Cuckoo filters have two advantages over Bloom filters:

1. They are more space efficient at false positive rates less than about 0.03.
2. You can delete items from them without affecting the false positive rate at all.

It seems to me that an in-memory cuckoo filter could work really well to keep track of Bitcoin's "unspent transaction output set" (UTXO set), to make transaction (or block) validation as fast as possible using minimal memory or disk.

Recall that Bitcoin transactions (other than coinbase transactions that create new coins) have inputs that refer to unspent outputs. An input refers to a previous output by giving the transaction id (a 32-byte hash) co

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sudo apt-get install -y php-pear php5-dev
sudo pecl install mongo

sudo sh -c "echo 'extension=mongo.so' > /etc/php5/mods-available/mongo.ini"
sudo ln -s /etc/php5/mods-available/mongo.ini /etc/php5/apache2/conf.d/mongo.ini

sudo service apache2 restart

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all: test libtest.so testmodule

libtest.so: libtest.c
	$(CC) -Wall -g -fPIC -shared -o $@ $? -lc

test: test_main.c libtest.o
	$(CC) -o $@ $?

testmodule: testmodule.c
	python setup.py build

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#Steps to install latest Laravel, LEMP on AWS Ubuntu 14.4 version. This tutorial is the improvised verision of this tutorial on Digitalocean based on my experience.

Install PHP 7 on Ubuntu

Run the following commands in sequence.

sudo apt-get install -y language-pack-en-base
sudo LC_ALL=en_US.UTF-8 add-apt-repository ppa:ondrej/php
sudo apt-get update
sudo apt-get install zip unzip

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The MIT License (MIT)

Copyright (c) 2013 bill@bunkat.com

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is

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Blockchain Rule Update Process

We recently rolled out two changes to the Bitcoin block acceptance rules (BIP16 and BIP30); this document records the lessons learned and makes recommendations for handling future blockchain rule changes.

Note: there are "soft" rule changes and "hard" rule changes. "Soft" changes tighten up the rules-- old software will accept all the blocks and transactions created by new software, but the opposite may not be true. "Soft" changes do not require the entire network of miners and merchants and users to upgrade or be left behind.

"Hard" changes modify the rules in a way that old, un-upgraded software consider illegal. At this point it is much, much more difficult (some might say impossible) to roll out "hard" changes, because they require every miner and merchant and user to upgrade.

Lessons Learned