My world is computational statistics and I thought I would try out forio-epicenter for creating applications. Clearly I am able to call Python functions from forio-epicenter. However, am I able to call a Python function that calls a C function?
That is possible, though it may be mildly tricky. You'll have to compile the C code to a shared library, and it'll have to be compiled for 64-bit Linux (Ubuntu, though that shouldn't really matter too much). That shared library will have to be uploaded to your model directory in Forio Epicenter.
For wrapping the C library, there are three possibilities, more or less. SWIG doesn't require any support from Forio to be usable, you'll build the Python wrapper off-line and upload it to your model directory. Cython or CFFI can both be supported, though as of this writing they aren't. If you're interested, let us know, and support can quickly be added for either of those solutions (and it is planned to do both eventually anyway).
Swig
Cython
Disclaimer: I currently work at Forio
Related
I want to evaluate the performance of Rascal for a given rewrite system that I've written. I'm wondering if there's a good way of doing it?
Ideally, I'd generate some compiled Java classes from the system and then run them manually against my inputs. Is there an easy or recommended way to do it?
Cheers,
One way to do this is to use the functions in the library util::Benchmark. Typically, you could write something like
cpuType( (){ call_the_function_I_want_to_observe(); } ). This will execute your function and print the cpu time used.
Note that Rascal can be executed in two ways: interpreted and compiled which makes a big difference when measuring performance. We are working hard at the moment to fully integrate the compiler in the Eclipse IDE, but a stand alone version is available as well. This can be called as java -Xss8m -jar rascal-0.8.4-SNAPSHOT.jar --compiledREPL followed by at least values for directories for sources (--src), and binaries (--bin). Here rascal-0.8.4-SNAPSHOT.jar (but most likely named differently) is downloaded from the https://update.rascal-mpl.org/console/rascal-shell-unstable.jar.
If you need more information, don't hesitate to ask for more details: this part of our tool chain is unfortunately still undocumented.
I'm working with ESP8266 and I don't want to use Lua for the whole project, I just want to run a few snippets of Lua code, received from wifi/sd card. I'd need to start a Lua environment and run the scripts, which would then eventually call some native functions for low level tasks. In other words, I just want to use Lua as simple scripting language (as it's intended to be) to implement some dynamic behavior. Is it possible? Is there any build of lualib for arduino?
Thanks in advance!
You can simply embed Lua in a extlibs/ folder for example and link to it when compiling your program.
There is existing Lua binaries but building it yourself is easy and better (as it's multiplatform).
OK, I know both answers told me I can just embed the code into my project, however, I found out I need to make some small changes. I made an example working project available here and the following list of changes had to be made:
The flags LUA_32BITS and LUA_USE_LONGJMP (C exception handling) were enabled
The following libraries were excluded: io, os, package, coroutine
The following functions were removed from C API: luaL_fileresult, luaL_execresult, luaL_loadfile, luaL_loadfilex, luaL_dofile, luaB_loadfile, luaB_dofile
Lua output messages are redirected to the Serial interface, check tinylua.h, tinylua.cpp and lauxlib.h to change this behavior
Hope this helps!
The ESP8266 has up to 4MB of program storage. Theoretically you can get up to 16MB as the datasheet specifies.
As I remember, compiling an amalgamated version of Lua (all sources in one file), occupies less than 100kb.
So, you can compile the Lua library and use it as needed on esp8266, even using Arduino IDE.
But you will get NAKED Lua if you do so... No nifty libraries to control Wifi, serial, SD, ports... You would have to provide that in C, or use NodeMCU code as you need.
You can try LuaJIT and access C code directly from Lua, cutting out the need for writing libraries. I have no idea of how you would compile it to Esp8266, or if anyone have tried this before, but you can do it "for science" and tell us how it turned out.
I want to open libraries, because currently I want to see the algorithms used for drawing, modify them and implement them in my program. For example: I have tried to create an algorithm on my own for lines. But I failed. And even if I had succeeded, I fear that it might not give the same result as the algorithm in the libraries. And I don't want this to happen. That's why I want to copy the algorithms used for the methods in libraries. And I really hope that this will help me create the application I'm currently working on and with other applications in the future.
I tried to open the libraries with a code editor. But I had troubles finding the libraries- I don't really know where are they placed nor in what files are their codes stored.
How to open a Java library? Or is there a place in the Internet where the code is uploaded?
It sounds like what you want is to get inside the standard Java libraries (so you can see the code for methods like Graphics.drawLine()).
You can download the source files from the same place you got the JDK, if you are on Windows or Linux. For the Mac, see this question. You can even set up Eclipse so that you can debug into that source as if it were your own code.
However, you will probably not find line-drawing code in Java in these libraries - the Graphics implementation will almost certainly use native methods, and may just call existing methods in the OS.
If you are specifically looking for line drawing algorithms, another option would be to look at the Wikipedia page for the Bresenham (aliased) or Wu (antialiased) algorithm.
Edit:
The part of a Graphics2D call that actually puts pixels on the screen is probably inside a system call and therefore the source would not be available.
A java vector graphics library like Batik might have source for some of these algorithms, but probably relies on the Graphics2D calls for most of them. So, you might look for a comprehensive vector graphics library written in a language other than Java, where those graphics calls do not already exist by default.
Alternately, checking the table of contents for a computer graphics book might point you at a variety of algorithms that you could look up on Wikipedia.
For any given library:
Make sure to obey all licenses when using another's code
If you are referring to the Java SDK source code, you can find it here: http://grepcode.com/
If the project is open source, you can usually just get the source from the project website. No problem, though make sure to obey their license.
If the project is NOT open source, well, then you're in a pickle licensing wise, so I do NOT endorse this, however, you would need to use a Java Decompiler such as JD-Gui
As far as what drawing algorithms to use, there are so many different ones (obviously, people have been trying to draw quickly for many many years), your best bet is to figure out exactly what you need to do and then search for that specific need separately. There isn't really a good repository of ALL of them, except maybe wikipedia.
If you are using the libraries they are on your classpath. Check out how to figure out your classpath in whichever IDE you are using and you can find the JARs you depend on. If they are packaged with sources all you need to do it unjar them and look at the sources.
If you don't have access to the sources you can get the code using a Java Decompiler.
If you are trying to look at a standard Java library, see the other answers about getting the source to the JDK.
If you are interested in an open source library (such as something maintained by the Apache project), look on the site of the project for a 'source jar' which you can open with a standard zip utility.
If the library you want is not open source or you cannot find the source for it, you can try to decompile it. If you are using Eclipse, try this decompiler.
How can I build and compile my own Lua files on Windows? And make them executable.
I am reading Beginning Lua programming, and I have Windows 7 and MacOS Lion both installed. I am having the hard time to follow the instructions. They do not work for me.
On MacOS I open the terminal and put these in:
export LUA_DIR=/usr/local/lib/lua/5.1
mkdir -p /usr/local/lib/lua/5.1 (it tells me, mkdir: illegal option) and I can not follow from here
SET LUA_DIR=”c:\program files\lua\5.1”
As for Windows I do this according to the book.
This what I see in my shell c:\Users\bd>
mkdir "c:\program files\utility" and it tells me access is denied
I have tried to right click on this folder and check off read only, but it does not work.
Any clues would be appreciated, this part has been really confusing for me.
To package your Lua files into an executable on Windows you have several options. There is srlua, there is wxLuaFreeze from wxLua (available as a binary for Windows), and there are more options in this SO answer.
Essentially, the main two options are: (1) append your Lua code to a precompiled exe file, such that it will be loaded and executed when that exe file is run, and (2) convert your Lua code into real executable by compiling it to bytecode, then to C, and then to your target platform.
As to your MacOS issue, mkdir -p means that mkdir is asked to create intermediate directories (for example, you asked to create /a/b/c, it will also create /a/b if those don't exist). As you don't say which version of MacOS you run, it's difficult to provide more detailed answer.
For now the standard distribution of Lua does not compile a script to native executable code; it execute your scripts by first compiling it to bytecode, then by interpreting the bytecode with a reasonnably fast static interpret (this also means that it is easily portable across native or virtual systems, and very resistant to attacks (that could be targetting bugs in the native compiler itself).
Also Lua still does not feature a runtime JIT compiler like Java and .Net: Lua still does not features a VM to produce a safe sandbox.
There exists Lua packages that convert your bytecode (or directly a source script) to a C source that can be used to convert a Lua library into native mode via the same C compiler used to compile the Lua engine itself (this is how the builtin libraries are produced, though they are slightly optimized manually in some time-critical parts).
However it is possible to compile Lua to a javascript source, and run it with fast performance using Javascript, because today's Javascript interprets do have good performance with their implemented VM featuring a JIT compiler for their own bytecodes.
It is also possible by converting it the Lua bytecode to a .Net or Java source that can then be executed directly from Lua (for that you need a version of Lua that has been ported to .Net or Java or Javascript, something that is not so complicate than developing in C/C++ directly a VM with a JIT compiler (a moderately complex part is the bytecode verifier, but the really complex part is the memory manager its garbage collector and its sandbox so that your Lua script will be fully isolated from the Lua engine itself for itw own memory, but the most complex part if the runtime optimizer and collection of profiling statistics: this has been done in the modern VMs for Java, .Net, Javascript, PHP/Zend, Python, Perl...).
I dont know which other language VM would offer the best performance to port Lua and implement on it a compiler to their own bytecode running at near native speed in their VM. But my own small experience with programs (in a much simpler language) self-generating a bytecode that they can run themselves, has always shown me Java winning in performance over .Net and Javascript. This is most probably because Java features an profiling-based dynamic code optimizer
(On the opposite the .Net optimizer runs only once during program installation, using some profiling data collected during the installation of the .Net VM itself, or at first instanciation of the script, without really knowing any profiling data collected during execution of the compiled program itself, and based on some cheked assumptions about the platform capabilities).
I also don't if would be faster in PHP, Python or Perl; the comparison with newer Javascript engines was never attempted though. Porting/compiling a Lua program to Javascript is relatively easy because it implements closures relatively easy for the resolution of linkages. Then the generated Javascript will compile to native code with the excellent Javascript's JIT compilers we have today (and never cease to improve in performance, so much that I've seen various appliactions running now faster in Javascript than before when they were written in C++ or plain C; as well the memory footprint has largely been reduced, we no longer have memory leaks, and even if there's a garbage collector, today's Javascript VM have a very efficient one, which is even better than the GC implemented in the native Lua).
But Lua remains useful as it is easy to secure and sandbox and offers various security benefits (but there are security issues in Lua as well for some kinds of applications, where Javascript offers some solutions, notably for side-channel attacks based on variation of time of execution; but these side-channel attacks are very hard to solve and can affect any system, any program, any programming language, and this starts becoming a critical issue because they are now more esily exploitable; the reason of that comes from hardware optimizations that we depend more and more today when we want to maximize the performances). And with Lua you may be more immune to these problems that a sandboxing sofware environment cannot solve alone.
Probably later we'll see a true VM implementation of Lua with a JIT and self-generating code and the possibility to instanciate new sandboxed VMs to run their self-generated code. It will take more time to generate an EXE file for distribution; notably because it generally requires adding also an installer and a distribution manager.
So for now we could imagine distributing Lua applications compiled to the bytecode of another JIT-capable VM: this generated bytecode would be faster than the Lua bytecode, and would then be extremely complex to reverse-engineer to the semantics of Lua because it would require two separate reverse engineering first from the bytecode of the other VM to the bytecode of Lua, both bytecodes loosing some easiy inferable rules and options tested and foll, and then again to sme Lua source
For the OSX terminal issue:
This command should work
export LUA_DIR=/usr/local/lib/lua/5.1
This command will probably give you permission problems:
mkdir -p /usr/local/lib/lua/5.1
You may try this to solve that. You will be prompted for your password:
sudo mkdir -p /usr/local/lib/lua/5.1
This command has nothing to do with OSX and will not work. This is a windows command:
SET LUA_DIR=”c:\program files\lua\5.1”
You have a permissions problem with Windows- try creating your cmd or PowerShell in Administrator mode. C:\Program Files is a protected directory that a regular user account doesn't have permission to write to.
As for the OS X issue, check out the mkdir OS X manual page to make sure you have the command correct.
So, if I understood your question correctly, you are trying to build Lua on Windows.
This is of course possible, but not easy for beginners. I would highly recommend you to use a binary distribution, which is much easier to install, unless you have special requirements.
Here are several Windows distributions :
Lua Binaries (Lua 5.1 and 5.2)
LuaForWindows (Lua 5.1)
LuaDist (Lua 5.2)
I am not even a newbie to erlang yet, I am just using RabbitMQ, which is written in Erlang. After I run configure/make/make install, the build output directories have plenty of .c and .erl files. Is this necessary? What's the reasoning behind it?
some examples:
./lib/erlang/lib/erl_interface-3.7.6/src/misc/show_msg.c
./lib/erlang/lib/cosNotification-1.1.18/src/oe_CosNotification.erl
Yes, it's necessary. The runtime system of Erlang is written in C, and most of the standard library is written in Erlang.
What's the reasoning behind it?
What would be the alternative? In order to execute any Erlang code, you need to have the runtime system already started, and so it can't be written in Erlang. It could be written in:
Assembly
C
C++ or some other language
Erlang could be executed without a runtime
Assembly is obviously a bad choice: you'd have to rewrite it nearly completely for any new CPU target and it would be much harder to maintain.
C provides excellent performance and portability, and ability to call C code from Erlang would at any rate be required. This is the choice made not only by Erlang, but by Python, Ruby, Perl, etc. as well.
C++ complicates portability (some OSes have C compilers available, but not C++ compilers; quality of C++ compilers varies more); other languages even more so (along with performance, possibly requiring their own runtime, etc.).
The final option would make Erlang a completely different language.