105 lines
5.2 KiB
Markdown
105 lines
5.2 KiB
Markdown
---
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title: Scripting
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...
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Initially we intend to implement human to human secret messaging, with
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money that can be transferred in the message, and the capability to make
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messages public and provably linked with an identity
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But obviously we are eventually going to need bot responses, and bot
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scripts that can interact with the recipient within a sandbox. Not wanting
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to repeat the mistakes of the internet, we will want the same bot language
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generating responses, and interacting with the recipient.
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There is a [list](https://github.com/dbohdan/embedded-scripting-languages){target="_blank"} of embeddable scripting languages.
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Lua and python are readily embeddable, but [the language shootout](https://benchmarksgame-team.pages.debian.net/benchmarksgame/) tells us
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they are terribly slow.
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[Embedding LuaJIT in 30 minutes]:https://en.blog.nic.cz/2015/08/12/embedding-luajit-in-30-minutes-or-so/
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{target="_blank"}
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Lua, however, has `LuaJIT`, which is about ten times faster than `Lua`, which
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makes it only about four or five times slower than JavaScript under
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`node.js`. It is highly portable, though I get the feeling that porting it to
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windows is going to be a pain, but then it is never going to be expected to
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call the windows file and gui operations.
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Other people say it is faster than JavaScript, but avoid comparison
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to Nodejs. But it is allegedly faster than any JavaScript I am likely to
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be able to embed.
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[Embedding LuaJIT in 30 minutes] gives as its example code a DNS
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server written in embedded LUA. Note that it is very easy to embed
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LUAJIT in such a way that the operations run amazingly slow.
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Web application firewall that is used by Cloudfare was rewritten from
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37000 lines of C to 2000 lines of lua. And it handles requests in
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2ms. But it needed profiling and all that to find the slowdown
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gotchas - everyone who uses LUA JIT winds up spending some time and
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effort to avoid horrible pointless slow operations and they need
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to know what they are doing.
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He recommends embedded LUA JIT as easier to embed and
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interface to C than straight LUA. Well, it would be easier for
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someone who has an good understanding of what is happening
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under the hood.
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He also addresses sandboxing. Seems that LUA JIT sandboxes just
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fine (unlike Javascript).
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Checking his links, it seems that embedded LUA JIT is widely used in
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many important applications that need to be fast and have a great
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deal of money behind them.
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LUA JIT is not available on the computer benchmarks shootout. The
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JIT people say the shootout maintainer is being hostile and difficult,
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the shootout maintainer is kind of apt to change the subject and
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imply the JIT people are not getting off their asses, but I can see
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they have done a decent amount of work to get their stuff included.
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LUA JIT is a significantly different dialect to LUA, and tends to get
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rather different idioms as a result of profiling driven optimization.
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It looks like common LUA idioms are apt to bite in LUA JIT for
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reasons that are not easy to intuit. Thus there is in effect some hand
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precompiling for LUA JIT.
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Anecdotal data on speed for LUA JIT:
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* lua-JIT is faster than Java-with-JIT (the sun Java), lua-JIT is faster than V8 (Javascript-with-JIT), etc, ...
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* As Justin Cormack notes in the comments to the answer below, it is crucial to remark that JITed calls to native C functions (rather than lua_CFunctions) are extremely fast (zero overhead) when using the LuaJIT ffi. That's a double win: you don't have to write bindings anymore, and you get on-the-metal performance. Using LJ to call into a C library can yield spooky-fast performance even when doing heavy work on the Lua side.
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* I am personally surprised at luajit's performance. We use it in the network space, and its performance is outstanding. I had used it in the past is a different manner, and its performance was 'ok'. Implementation architecture really is important with this framework. You can get C perf, with minimal effort. There are limitations, but we have worked around all of them now. Highly recommended.
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Lisp is sort of embeddable, startlingly fast, and is enormously capable, but
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it is huge, and not all that portable.
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ES (JavaScript) is impressively fast in its node.js implementation, which does
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not necessarily imply the embeddable versions are fast.
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Very few of the scripting languages make promises about sandbox
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capability, and I know there is enormous grief over sandboxing JavaScript.
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It can be done, but it is a big project.
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Angelscript *does* make promises about sandbox capability, but I have
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absolutely no information its capability and performance.
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Tcl is event loop oriented.
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But hell, I have an event loop. I want my events to put data in memory,
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then launch a script for the event, the script does something with the data,
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generates some new data, fires some events that will make use of the data, and
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finishes.
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Given that I want programs to be short and quickly terminate, maybe we
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do not need dynamic memory management and garbage collection.
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Lua is slowed by dynamic memory management. But with event
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orientation, dynamic memory management is complete waste, since your
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only memory management is allocating continuation objects to be fired on
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the next event - which is to say, all memory management is explicit, when
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an event handler detaches.
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