Threading Functions with Arguments

Programming Support
#1

Hello, I have a function that I need to put on a separate thread.

I have a few arguments that I need to pass to the function that I’m threading.

How would I

1: Create a thread
2: Pass arguments to the function that thread is running
3: Start the thread

Thanks for any responses!

2 Likes
My task isnt working
#2

@jpearman help papi

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

#3

Assuming you’re using VEXcode C++, you can pass the parameters as additional arguments to the thread constructor.

void myThreadedFunction(int a, int b){
    // do some stuff here
}

int main(void){
    // create & start the thread
    thread myThread = thread(myThreadedFunction, 42, 314);
}

If you’re using PROS I would imagine you can do something similar.

3 Likes
#4

code not work, error hapen

poop.
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀v

#5

here thing btw

Thing i wanna thread:
void bindTwoMotorsToButtons(
controller::button &btn1,
controller::button &btn2,
int speed,
motor m
) {
while (true) {
if (btn1.pressing()) {
m.spin(directionType::fwd, 100, velocityUnits::pct);
} else if (btn2.pressing()) {
m.spin(directionType::rev, 100, velocityUnits::pct);
} else {
m.stop();
}
this_thread::sleep_for(20);
}
}

code for threading:
thread myThread = thread(bindTwoMotorsToButtons, Controller1.ButtonL1, Controller1.ButtonL2, 100, LiftClaw);

error:
[clang] No matching constructor for initialization of ‘vex::thread’

still poop

#6

I believe you are referring to multi-tasking correct?
If you would like to do that, you first need to make a function:

void drivePID(){

//Do stuff

}

Then, whenever you would like to run this as a separate task, you can do the following in code that is ran:

void autonomous(void) {

vex::task billWiTheScienceFi(drivePID);

}

I don’t know how to pass parameters directly this way, but you can always use global variables. Here’s what I mean:


int a;

int drivePID(){
  if a == 50{
    //Do Stuff
  }
}

void autonomous(void) {
  a = 50;
  vex::task billWiTheScienceFi(drivePID);
}
2 Likes
#7

yeah i guess that would work, putting them in global variables kindof sussy ngl.

it doesnt seem very clean saying i know that there is a cleaner was to pass the arguments.

seems like it will work, will do.

thanks bb

:heart:

2 Likes
#8

It honestly is sketch, and I bet there’s better alternatives. But until there’s anything better presented then I hope that can be a good ‘patch’ until someone like @jpearman hops on to help out :slight_smile:

#9

the patch shall work, until daddy pearman revives himself i will stick with the sussy global variable method

2 Likes
#10

Seriously, we are all on holiday and really have better things to do, but this is something I posted before I think.

example code 
/*----------------------------------------------------------------------------*/
/*                                                                            */
/*    Module:       main.cpp                                                  */
/*    Author:       james                                                     */
/*    Created:      Wed Dec 29 2021                                           */
/*    Description:  V5 project                                                */
/*                                                                            */
/*----------------------------------------------------------------------------*/

// ---- START VEXCODE CONFIGURED DEVICES ----
// ---- END VEXCODE CONFIGURED DEVICES ----

#include "vex.h"

using namespace vex;

typedef struct _mydata {
    int para1;
    int para2;
} mydata;

mydata Mydata;

int taskWithArg( void *arg ) {
  mydata *d = (mydata *)arg;

  printf("taskWithArg %d %d\n", d->para1, d->para2 );

  return 0;
}

int anotherTask( void *arg ) {
  int *x = (int *)arg;

  printf("anotherTask %d\n", *x );

  return 0;
}

int main() {
  // pass a structure  
  Mydata.para1 = 9;
  Mydata.para2 = 28;
  task t1( taskWithArg, (void *)&Mydata );
  
  // if passing a local variable, make sure it doesn't go
  // out of scope.
  int  x = 8;
  task t3( anotherTask, (void *)&x );

  while(1)
    this_thread::sleep_for(10);
}

You can pass exactly one void pointer to a task.

9 Likes
#11

thank you so much papi, this code with make my driver code impeccable. i will not let you down