Hello! I have started using AS and it's been a blast. The best scripting language I have used hands down.

But now I have hit a hurdle. I'm making a block based system - you take many blocks and link them all together. Every block is programmed in AS and threaded. Now the question is which parts I can thread? The doc's says the engine is totally thread safe if I only use one. Couldn't see anything specific about contexts or modules. Recent commits seems to have put locks on modules though (haven't tested the WIP version), which seems to me that it wasn't thread safe. I have tried this:

//This is done once
asPrepareMultithread();
asIScriptEngine *engine = asCreateScriptEngine(ANGELSCRIPT_VERSION);

//Then in each thread:
asIScriptContext *ctx = engine->CreateContext();

string code;
as::LoadScriptFile(script, code);

asAcquireExclusiveLock();
asIScriptModule *mod = engine->GetModule("my_module", asGM_ALWAYS_CREATE);
asReleaseExclusiveLock();

mod->AddScriptSection("my_module", code.c_str());
// Build the module
int r = mod->Build();
if( r < 0 )
{
  printf("Please correct the errors in the script and try again.\n");
  return;
}

asIScriptFunction *func = mod->GetFunctionByDecl("void main()");
if( func == 0 )
{
  printf("The script must have the function %s. Please add it and try again.\n", function.c_str());
  return -1;
}

while (true){ //This executes the function in the thread until it breaks
  ctx->Prepare(func);
  int r = ctx->Execute();
  if (thread_break == true) break;
}

ctx->Release();
asThreadCleanup();

//Here threads end

The problem here is that it sometimes crashes. When I put asAcquireExclusiveLock(); around every as call then it doesn't, but then it impacts the framerate as it stalls for large amount of time. So what else needs to be locked specify? I could experiment and find out, but I would like to know what is recommend. Like if GetModule are not thread safe, then is GetFunctionByDecl neither? What is thread specific? Like can I call a function from the same context in two threads the same time (if they don't have any shared or global variables)? Do I need to Release "function" pointers just like I need to release contexts and engines?

And I seem to have problems with "Script section empty" error. I have tried several methods on loading files and I don't know why, but it sometimes fails. I tried the ScriptBuilder, as well as code from "Compiling scripts" section of the docs. When I have this error, I have to modify and save the file again for it to load. I do autoload files though based on their modify date, which could be the issue (I load it before it has finished writing on the disk??). I will add a delay and see if that helps. I do see that in threads formatInt() and other string functions crashes. Not sure if I'm at fault.

Another question is about variable sharing.

I need to have several blocks, like "BlockA" and "BlockB". I need have several instances of the same block, like "BlockA1" and "BlockA2". Then I need to execute the blocks in parallel without them interfering with one another. In AS terms each of my unique blocks (A and B) would be separate modules - "ModuleA" and "ModuleB". Then separate instances of blocks would be different contexts "ContextA1" and "ContextA2" right? So if contexts are different, then they won't interfere with one another? Like I need them to have global variables (declared outside any function, so it holds the state if you will), because each block is made out of several functions. Like this:

int s = 0; //State that doesn't change between function calls

void funcInit(){ //This is called from C++
 s = 5;
}

void funcUpdate(){
 s = s + 1; //This changes the state and is called from C++
}

I guess this is how something like that would work?

Thank you for all the answers.

You should however be aware that the Build() call will fail with return code asBUILD_IN_PROGRESS if another thread happen to be compiling a script at the moment, so you'll need to add logic to wait and retry if you don't want your code to fail completely in this case.

This might be the issue. I ran Build on several threads thinking it will just wait internally. I will probably do your queue method later, but right now I just did while (r == asBUILD_IN_PROGRESS) r = mod->Build(). For now I haven't gotten the empty section error.

You don't need to 'release' function pointers received from GetFunctionByDecl(). I specifically mention in the manual the pointers that needs to be released, but as a general rule any function named 'Get' will return the pointer without increasing the reference counter, and any function named 'Create' will return a pointer that has to be released afterwards.

Good tip! It's just that GetModule() also creates the module (with proper flag or when using scriptbuilder) and so I was just thinking GetFunction also does that. Only when function->Released() crashed my program did I came to realize it's somehow different.

formatInt (from scriptstdstring.cpp add-on) should be thread safe as long as you make sure to link with the multi-threaded version of the C-runtime library.

I compile with GCC and -pthread flag (which links with -lpthread and defines the -D_REENTRANT. I also tried disabling string pool thinking it might not be thread safe, but after looking at the formatInt function I don't see why it would crash for me. It just does sprintf.

So I went back to no-threading just to see if the problem is somewhere else. And weirdly enough it now crashes without threads too. It did work previously though, so I'm not sure what's the problem. Will look into this in the morning.

When I fix my integer to string problem I will look into how to deal with globals painlessly.

edit: 30 seconds after posting I tried another thing which I totally forgotten - I use Jit by BlindMindStudios. And I haven't tried formatInt with Jit. It turns out that it is the reason why it crashes. If I remove Jit the function works fine. Can anyone replicate this?

I have weird results with globals. The docs doesn't say how the globals a defined, it just says:

Global variables may be declared in the scripts, which will then be shared between all contexts accessing the script module.

Variables declared globally like this are accessible from all functions."

Which is okay, as I understand "global" as in C++ global. That means in script like this:

int a = 0; //This is global
void main(){
  print("A = "+formatInt(a,"")+"\n");
  ++a;
}

the int a is global right? I get confirmation on my theory when I set "SetEngineProperty(asEP_DISALLOW_GLOBAL_VARS, true)" which makes the script error out because of the global variable. But if I load the same code in two theads with two contexts (but the same module name) I get this output:

A = 0
A = 1
A = 2
A = 3
A = 4
A = 5
A = 6
A = 7
A = 8
A = 9
A = 0
A = 10
A = 11
A = 12
A = 13
A = 14
A = 15
A = 16
A = 17
A = 18
A = 19
A = 20
A = 1
A = 21
A = 22
A = 23
A = 24
A = 25
A = 26
A = 27
A = 28
A = 29
A = 30
A = 31
A = 2
A = 32
A = 33
A = 34
A = 35
A = 36
A = 37
A = 38
A = 39
A = 40
A = 41
A = 42
A = 3

One thread sleeps for 100ms after each script call, while the other sleeps 1100ms. I would expect to see a getting incremented all the time, but here the two threads use a different variable "a". If a is global, then it should be shared by contexts within a module no?

This is actually what I need and what I want, but it contradicts the docs. Maybe I'm doing something wrong.

And how would I create a unqiue struct instance inside AS? I want to make a system where a person can create all the things he needs only using scripts, so he wouldn't need to create a C++ struct and pass it in. So I get that I can do this:

struct number{
  int a;
}

void init(){
  number n;
  n.a = 5;
}

void update(){
  //How to access unique number.a? I could access global a here.
}

But each execution will have the same object?