java本身没有问题，速度和c++差不多，问题是牛人都用c++开发，次牛的才用java

Quote from: ptsrush on February 14, 2014, 02:23:01 pm

纯属个人偏见。

我用过的 java 软件，例如 OpenOffice，Azureus(现在叫Vuze)，Eclipse，
以及各种 EJB，Android 应用等，无不庞大缓慢。

拼命吹嘘说 JIT 编译可超过 C++ 性能，实际运行慢如蜗牛。

而且内存占用永无止境。

msc / xcp 都是依附于 btc 的。

btc 的设计目标和 msc / xcp 不同。

照理讲应该是 msc / xcp 是货车，btc 是货物，msc / xcp 拉着 btc 跑。

现在反而要货物拉着货车跑，比较神奇。

关于实现Blockchain所用的DB，有很多有趣的讨论，Bitcloud最近比较活跃，有一些讨论，不同于levelDB和BDB此类key-value db， 有尝试用Sqlite此类的关系数据库：

Quote

Javier R. Sobrino liberman@riseup.net via lists.sourceforge.net
11:58 PM (10 hours ago)

to Bitcloud

While I was designing the blockchain for Bitcloud, I realized that there
is no way that Bitcloud can work on a classical Blockchain structure.

Just imagine: Bitcoin with 1 million users needs 12Gbytes of data to
store the blockchain, and what it stores is just money
transactions. Bitcloud is going to store many other things, like node
statistics, user and publishers information, sophisticated contracts,
etc. If we use an immutable form of blockchain, in one month after the
release we will need hundreds of gigabytes only to store that.

Another limitation of the classical blockchain is that it is not
relational, so you can't do advanced queries without going into a lot
code. To see that, look at how I am designing the nodepool here:

https://github.com/wetube/bitcloud/blob/master/src/c/nodepool.sql

Handling the logic of all of that in a key-value database is very hard.

So my proposition here is to stop thinking in terms of the classical
blockchain and approach this project from a different perspective.

As I say in the paper: the Nodepool is a relational database, synced by
consensus, in which all the statistics, information and contracts are
stored.

In my investigations to find a proper database that could support all
the things we need, I found that SQLite is very nice, and can be easily
tweaked and extended.

SQLite supports the creation of custom checks, so something like this
can be possible:

CREATE TABLE publisher_grid_contracts (
 id BLOB(16) PRIMARY KEY NOT NULL,
 publisher TEXT NOT NULL REFERENCES publishers(public_key),
 grid TEXT NOT NULL REFERENCES grids(public_key),
 -- Signatures of this contract:
 publisher_sig TEXT NOT NULL,
 grid_sig TEXT NOT NULL,
 -- Terms:
 min_storage INTEGER NOT NULL,
 min_bandwidth INTEGER NOT NULL,
 start_date DATE DEFAULT CURRENT_TIMESTAMP NOT NULL,
 end_date DATE DEFAULT CURRENT_TIMESTAMP NOT NULL,
 availability INTEGER NOT NULL, -- % of time online
 ping_average INTEGER DEFAULT 0,
 -- Coin terms
 coin REFERENCES coins(id)
 CHECK (signatures(publisher_sig, grid_sig,
   publisher || grid || min_storage || min_bandwidth ||
   start_date || end_date || availability || ping_average ||
   coin )
);

Look at the last statement, the "CHECK(signatures...." one. Once we
define the extension "signatures" in plain C, we can ensure that nobody
can insert a contract into the database without the proper signature of
the two participants of the contract.

But there is even more. SQLite also allows to customize an authorization
function to allow or deny access to data from different sources, which
means that we can base the language of Bitcloud in SQL, and only allow
certain operations. Look at:
http://www.sqlite.org/capi3ref.html#sqlite3_set_authorizer

I strongly recommend everybody to have a look at this fantastic book:

http://evalenzu.mat.utfsm.cl/Docencia/2012/SQLite.pdf


Now, having SQLite resolving our problems for the language and the
database, we can concentrate on the sync process.

Any suggestion, questions or alternatives to all of this, please answer
to the list.

Thanks.

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