lua function call overhead

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I would generally recommend to avoid making high volume calls into Lua. First, load the FFI library and declare the low-level data type. These are three different types of function calls: Through the PLT. The API protocol to call a function is simple: First, you push the function to be . Such files would then be listed under something like [LuaFiles.profile_name] in the FSUIPC ini file. A common such task is profiling. However, for counting profiles, Lua code does a decent job. These are a bit more tidy than the do block approach but do impose the load-time overhead of at least constructing a temporary function. Functions are functions are functions in Lua, they are all equally fast. Don't know if other types in lua can have metatables set to them, or if that's just exclusive to tables. The returned values are an array of objects, corresponding to Lua multiple returned values. An indirect function call (via dlsym (3)) A direct function call (via a JIT-compiled function) As shown, the last one is the fastest. delayedexecute.lua. Wow. Usage suggestions. Running Lua functions in TeX. Otherwise, this falls to the implementation-defined behavior of your Lua VM, whereupon is may add keys into empty 'holes' in the array . Here are the results on an Intel i7-6700 (Skylake): plt: 1.759799 ns/call ind: 1.257125 ns/call jit: 1.008108 ns/call. Type functions supporting dependent kinds, and equality constraints, Rank-N, impredicative types via Quick Look: quantifiers can appear anywhere in a type . First, it allows two or more parallel iterations. The program must support a command-line interface. It behaves somewhat like a stack as in [Forth] but with one element. Lua 5.4 adds a new function, lua_setcstacklimit, but this merely exposes what was a compile-time constant, LUAI_MAXCCALLS, in earlier versions. Using this is also simple. Values associated with some Fibaro variables are predefined i.e. Most analyzers' overhead is usually unmeasurable, even during the sampling window. So templates can call Lua modules, parser functions and pages in MediaWiki namespace. lua_sethook () is the only safe Lua function to call from an asynchronous thread (or signal handler) as it just sets a flag in the Lua VM . Fennel is a programming language that brings together the speed, simplicity, and reach of Lua with the flexibility of a lisp syntax and macro system.. Full Lua compatibility: Easily call any Lua function or library from Fennel and vice-versa. Calling down into Lua 100,000,000 times took nearly 13 seconds. Lua code can call C functions directly. Can templates, MediaWiki pages or parser functions be called from Lua? The program must support a command-line interface. Apparently if that method is defined, you can call a table as if it's a function. -----Original Message----- From: lua-bounces@bazar2.conectiva.com.br [mailto:lua-bounces@bazar2.conectiva.com.br] On Behalf Of Nguyen Dang Quang Sent: Wednesday, July 19, 2006 12:24 PM To: 'Lua list' Subject: RE: call a function in other script from a script Hi Daniel, My trouble is: In File 2: Function some_other_functions(xxx) End function main() --do . Update 31: The New War; Update 30: Call of the Tempestarii; Update 29: The Heart of Deimos; Update 28: The Deadlock Protocol; Update 27: Empyrean; Update 26: The Old Blood A great strength of Lua is that a configuration file can define functions to be called by the application. When I call a function in lua script, I found that the main cost is luaL_ref() and LuaL_unref()Is this necessary?SolCall will be much more slower than luaCall() because of the extra function call overhead. tinsert . . Neither will start to process until the Lua code has return to is calling C function. Aerospike provides examples of compiling and registering a . > s = "hello dolly" > print(s:find("(dolly)")) 7 11 dolly Actually, it means _ENV.table.insert - _ENV is where the "global variables" are in Lua 5.2+. It took about 97ms to call the C++ square function 100,000,000 times. Details are given below. This does avoid the overhead . Fennel is a programming language that brings together the speed, simplicity and reach of Lua with the flexibility of a lisp syntax and macro system. PICO-8 has this nice helper function called foreach (table, func) which will call the function for each item. Zero overhead: Compiled code should be just as or more efficient than hand-written Lua. Calling Titan from Lua (and vice versa) should be very cheap function sum_list(xs: {integer}) : integer local sum: integer = 0 for i: integer = 1, #xs do sum = sum + xs[i] end return sum end Calling into Lua and running the square function was about 130 times slower than just calling the C++ function. There are a few reasons why you may. . A __call field added to a regular table (x in your example) does nothing. Calling external programs via the command-line interface, using Lua functions like os.execute() or io.popen(). Formal function arguments receive a default value of nil if they are not filled. The overhead is high to access Lua global data, especially tables and functions. Fennel is a programming language that brings together the speed, simplicity and reach of Lua with the flexibility of a lisp syntax and macro system. The way to handle this is to hook into the Lua VM in the signal handler. Stacking up such requests in a single Lua task function burns scarce RAM and can trigger a PANIC. So, in conclusion, calling from Lua to C++ is great. Compile-time macros: Ship compiled code with no runtime dependency . For a profile with timing, it is better to use the C interface: The overhead of a Lua call for each hook is too high and usually invalidates any measure. Translating all this to human terms, yielding is only possible when C isn't using the Lua stack for its own calls. In building a solution that allows us to register C++ classes to Lua, we must make use of those extension mechanisms. but for any normal codebase this overhead is minimal. On the one hand, it is easier to write the iterator with this second style (although we can recover this easiness with coroutines). The upside is that like the previous approach, this scales well to a large number of object instances due to the low per object overhead but unlike the previous approach, it . Just keep in mind that 'statusline' is evaluated quite often, so the overhead of using a Lua function call from there might become quite noticeable and produce lag while editing. Lua 5.1 has something similar but it's not called _ENV. function Lua_signal_handler () print ("Hi! The correct way is to make the following edits in the bench.lua file: Put the call into a Lua function named target. A number of the string functions work like this,for instance, string.findwill return the start index and end index of the match, plus any captures. when a lua script is called, (in luaRedisGenericCommand) it is called via the "call()" function which uses server.lua_client and calls lots of addReply()s. this generates a response like ":3\r\n:4\r\n:5\r\n" which is parsed by the function redisProtocolToLuaType() which puts the integers [3,4,5] onto lua's stack. If the for has other variables, they simply get the extra values returned by each call to f. Share Improve this answer It's a bad idea to call a user-defined Lua function from C code millions of times. This data structure is a kind of unique session variable allowing multiple Lua scripting engine . A string "hi" for example can have multiple variables pointing to it. . Here we choose a struct which holds four byte fields, one for each componentof a 4x8 bit RGBA pixel. because you are producing a bit of overhead by using table.pack, . That is partly about performance but mostly about engine architecture. Here we choose a struct which holds four byte fields, one for each component of a 4x8 bit RGBA pixel. Because of the need to store 64-bit double precision numbers and 64-bit pointers, we don't use NaN tagging and have to pay the cost of 16 bytes per value.. We take advantage of this to provide a native value type that can store a 32-bit floating point . The role of __call is to make something that is not a function (usually a table) act like a function. I was wondering if in a future version of FSUIPC this limit could be extended by designating certain Lua files to be aircraft (profile) specific Lua files. For instance, we have already called print with one, two, and more arguments. Each function is as thin and fast an implementation as is possible within that host Lua environment, evaluating to the Lua C implementation with no overhead where host semantics allow. A Lua function call can return multiple values. SWIG offers no header files for your C++ code; it intends to be a one-way wrapper, to allow Lua to call your C++ functions. Lua: --[[ DelayedExecute v1.0.3 by AGD | Description: Small Lua . 25.2 - Calling Lua Functions. The author works around the issue by gluing strings together to effectively rewrite the pipeline into one nested function call. Suppose now that we want to redefine print in Lua: Perhaps our system does not have a stdout and so, instead of printing its arguments, print stores them in a global . I would not recommend using lua_rawcall () outside of a callback in case something goes wrong during execution. Creating the data structure with ffi.new () is straightforward the '?' is a placeholder for the number of elements of a variable-length array. Some functions in Lua receive a variable number of arguments. The trouble is that most of the time I want to call a method (table-bound function) instead of a function. . LuaJIT stated that globals and locals now has the same performance unlike in plain Lua. Here is what I want to be able to write in Lua: pipe(1, 100000) { range function(xs) return map(xs, function(x) return x * 3 end) end, function(xs) return filter(xs, is_odd) end, sum } . This concept might be extended to support more than one memory location: The issue here is that both Animation and OnUpdate calls have overhead that applies every frame while they are active. Answer: __call is a metamethod, that means it is meant to be defined in a metatable. The overhead of a setjmp () call for exceptions (and a few other things) is avoided. To get the perf bit out of the way: the bridging code between C++/Lua has overhead compared to just calling Lua from Lua or calling C++ from C++. . Native vector math. Both styles have approximately the same overhead: one function call per iteration. Lua modules are treated like the bodies of Lua functions so that they can both receive arguments and return values. 5. The call rawget (t,i) does a raw access to table t . . Full Lua compatibility: Easily call any Lua function or library from Fennel and vice-versa. There is the overhead of starting up the program, so this method is typically not so suitable if you need to call the code, say, thousands of times per second. local soundit = ( function () local sounds = { a = "ay" , b = "bee" , c = "see" , .. } return function (x) assert ( type (x) == "string" ) return sounds [x] end end ) () However, creating the same function (closure) over and over again inside a busy loop, . lit install Samur3i/direct-loader Usage And then call this function first for 100 times as a warmup. LuaJIT stated that it's faster than Lua. lua_sethook () is the only safe Lua function to call from an asynchronous thread (or signal handler) as it just sets a flag in the Lua VM . I like to use this in my _draw function to dispatch drawing to game objects. At its most basic, LuaAutoC can be used to automatically call C functions from the Lua API. Now, as to your question about efficiency; all function calls have a minimal overhead. The definition of appends here is only well-defined for a table which has a perfectly sequential (and integral) ordering of numeric keys with associated non-null values (the same requirement for the size function). As you know do some functions like 'CreateAuction' require a hardware event and my first approach was writing the PerformanceCounter to LastHardwareEvent (aka anti-afk) aswell as moving the value into LastHardwareAction via asm directly before calling the lua functions (Tried it with every single function GetTop, LoadBuffer, PCall and ToLString . Some full-instrumentation tools may incur higher overhead, like a cost of . 5.2 - Variable Number of Arguments. When we want to access a table without invoking its __index metamethod, we use the rawget function. Zero overhead: Compiled code should be just . A solution that uses some caching should be used to avoid that, either a Vim global variable updated from an autocmd (such as CursorHold, CursorMoved, CursorMovedI . If you are running each script only once you don't need to use lua_dump/lua_load, just do something like luaL_dofile followed by lua_pcall on the entry function, then move on (ie load the next file). If the Lua function does not have any arguments, there is a way of calling it with much less parsing overhead. function Lua_signal_handler () print ("Hi! Since Lua is dynamically typed and has no need for function type declaration, checking the number and type of arguments required for a function seems somewhat redundant. The goal is to interface with C code and C data types with a minimum of overhead. PICO-8 Generic Dispatch with Parameters. "Lua time used" is just the time inside Lua, and doesn't include things like #invoke overhead. So, if our iterator function is f, the invariant state is s, and the initial value for the control variable is a 0, the control variable will loop over the values a 1 = f(s, a 0), a 2 = f(s, a 1), and so on, until a i is nil. Any method is ok, unpack4 is the slowest probably because of the function call overhead. The callback overhead will be absolutely detrimental for performance. The Lua time usage should be fairly consistent for multiple parses of the exact same input . The baseCcalls is set to the nCcalls + 1 by resume. Lua provides self, but requires the user to distinguish between a regular function call, string.sub(strname, 2, 3) and a method call strname:sub(2, 3). This function returns true if the call was transferred by another user and is not a direct call. Compile-time macros: Ship . Lua objects, including strings, get garbage collected if nothing points to them. That overhead might be removed if we made save/restore a built-in operation in Lua. This function appends a value to a table. . Please see the Introduction chapter for some usage instructions.----- IsCallTransferred---- Checks if the current call was transferred to the current user,-- i.e. Installation You can download the latest release manually and include it in your project, or you can install it in your project directory through Luvit's package manager Lit, using the install command. Here is the case: script.lua: . The important thing to keep in mind is that drawing things to the screen outside of the love.draw () function, or functions called from that one, will have no effect, because the screen is cleared before love.draw () is invoked in your main.lua script. The os.exit() Lua function call will trigger the lj_cf_os_exit() . Now this target function should be JIT compiled after this loop is executed. 23.3 - Profiles. Second, Lua functions are dynamically allocated ('boxed'.) Lua deals gracefully with mismatched numbers of calling and formal function arguments. function make_line(m,c) return function (x) return m*x + c end end local line = make_line(1,2) -- as before. Fibaro global variables are pre-defined to the Fibaro environment using the Home Center -> Panels -> Variables user interface (note: these are not the same as Lua global variables). The important thing to keep in mind is that drawing things to the screen outside of the love.draw () function, or functions called from that one, will have no effect, because the screen is cleared before love.draw () is invoked in your main.lua script. When we perform a virtual function call, knowing which function is called we can infer an offset in the array to use and simply call the correct virtual function pointer. lua_call (the normal function to call a C / lua using the Lua stack from C) also uses luaD_call. When the target application reaches maximum throughput, the cost of sampling is generally under 5% of the throughput. In contrast, the new C_Timer . A separate node.flashindex() function creates a new Lua closure based on a module loaded into LFS and more specfically its flash-based prototype; whilst this access function is not transparent at a coding level, this is no different functionally than already having to handle lua and lc files and the existing range of load functions (load . it probably wouldn't hurt to subtract from those the runtime of a loop calling a (localized) empty function with the same number of iterations. Although the overhead to do so is measurable, it is simple. Lua can't avoid making some use of the C stack as it supports intermingling of lua_call's from C code with in-language VM calls, which necessarily will use some amount of C stack. A common such task is profiling. (3) reading out Lua values from Lua stack. Thanks I have solved my problem! Details are given below. However, for counting profiles, Lua code does a decent job. For Animations, we're doing work C-side that allows us to support smoothing, parallel animations, and animation propagation. Creating the datastructure with ffi.new () is straightforward the '?' is a placeholder for the number of elements of avariable-length array. there is a finite set of defined values, others may have any value in either case the variable name . It is even the case for actions such as requesting a system restart, as can be seen by the following example: Fennel . These benchmark tests demonstrate the performance of LuaJIT compiler, LuaJIT interpreter and Lua 5.1. The advantage disappears if the expression a is a nested table -- e.g. The way to handle this is to hook into the Lua VM in the signal handler. The principle is that every time you write table.insert for example, the Lua interpreter looks up the "insert" entry in the table called table. Despite its name, the debug library is useful for tasks other than debugging. Zero overhead: Compiled code should be just as efficient as hand-written Lua. Full Lua compatibility: Easily call any Lua function or library from Fennel and vice-versa. Support arguments to a protected function call, even on Lua 5.1. math.tointeger (x) Convert to an integer and return if possible, otherwise nil. Iterative multi-file loader, used to load all Lua modules in a directory and return them as one table. The solution There are four components that make the solution, class registration, object instantiation, member function calling, and garbage collection. Then when the Lua VM is at a safe spot, the hook is call which can then run the Lua function. Luau uses tagged value storage - each value contains a type tag and the data that represents the value of a given type. Calling external programs via the command-line interface, using Lua functions like os.execute() or io.popen(). . for some things you might be timing the function call overhead could be fairly significant Despite its name, the debug library is useful for tasks other than debugging. These return values are visible within Lua as the return values of a require() call and are visible within C as the items left on the Lua stack after a call to luaL_dofile() or another function that executes a block of Lua code. If you are . Doing a raw access will not speed up your code (the overhead of a function call kills any gain you could have), but sometimes you need it, as we will see later. Zero overhead: Compiled code should be just as efficient as hand-written Lua. I tweaked the Lua compiler a smidge to, if a compile-time symbol is defined, have Lua do call-counting profiling for all functions without any function-call overhead; it just adds a fetch,add,store to the start of every function. The Lua code for computing the sum of all . For OnUpdate, the overhead lies in the extra function call to Lua. Then when the Lua VM is at a safe spot, the hook is call which can then run the Lua function. While OO can also be encoded using closures capturing the instance, it has a big memory cost since one method closure needs to be allocated per object method and per instance (or lazily every . Yield later reads this C call count to determine if a C boundary is crossed. This means you can do anything you can do from C: access all memory, overwrite anything in memory, . Lua stack arguments are automatically popped and converted to C types, the function is executed, and the return value is then converted back to a Lua type and placed on top the stack. In your C callback functions, use lua_rawcall () to call other functions. C++ can return objects to Lua, but there's no mechanism for calling Lua functions from C++ with objects wrapped with the SWIG magic - which is rather obscure, and tangled in static functions within the .cpp files it . On the other hand, the generator style is more flexible. Now, as to your question about efficiency; all function calls have a minimal overhead. To answer: using a single lua_State will be faster if you need to load any standard libraries (the overhead is noticeable). I understand that currently the number of Lua files is limited to 128 (0 to 127). Lua VBScript . was in some other user's call routing before. but again this is function call overhead, only measurable with millions of iterations. Fennel . This true for timer, network, and other callbacks. For example, we can put the table printing function into slot 1 of LuaTeX's function table and call it with \luafunction1. Fennel is a programming language that brings together the speed, simplicity, and reach of Lua with the flexibility of a lisp syntax and macro system.. Full Lua compatibility: Easily call any Lua function or library from Fennel and vice-versa. Zero overhead: Compiled code should be just as efficient as hand-written Lua. First, load the FFIlibrary and declare the low-level data type. Titan plays along with Lua Titan modules can be require-ed from Lua Titan can work with Lua datatypes Titan shares the Lua garbage collector. LuaFunction has a Call function with variable parameters, and you can transfer any type and any number of parameters. quickly master the essentials of Lua programming. There is the overhead of starting up the program, so this method is typically not so suitable if you need to call the code, say, thousands of times per second. You can pass multiple Lua files to the testy.lua script, or you can pass the -r command line flag, which causes testy.lua to also collect test functions from require d Lua modules recursively. For a profile with timing, it is better to use the C interface: The overhead of a Lua call for each hook is too high and usually invalidates any measure. In contrast to OpenCL, the script is not compiled to native machine code, so some additional overhead for executing each operation in the Lua function is expected. . Rust closures are harder for three main reasons: The first is that it is both statically and strongly typed, so we'll need to explicitly annotate these function types. Lua has been used to great effect in a number of similar projects, such as arbitrary re-write rules within the Apache Squid proxy, UDFs in both Redis and Postgres, and other projects. local str1 = "hi" local str2 = "hi" It would make total sense if that's the case, because let's say you did local str1 = "hi" local str2 = "hi" str1 = nil Full Lua compatibility: Easily call any Lua function or library from Fennel and vice-versa. For instance, you can write an application to plot the graph of a function and use Lua to define the functions to be plotted. It's more terse, though at the expense of the function call overhead. The reason for choosing Lua is that a Lua script is just-in-time-compiled at run time and callable from a C API, just like OpenCL kernels. And then inside the timed code region, we call it repeatedly for 10 million times.