Worrisome Engine Behavior > Stack included!

[makeshyft]

Hi everyone,

I made this stack in order to simulate the generation of ID numbers to see the probability of duplicates. It consists of basically a simple loop that checks for matches blah blah blah

Everything works fine, except that Livecode becomes unstable (both in IDE and standalone) once the numbers get a little higher and it has to do more work.

Sometimes it takes a click away from the window, or inside the window, and sometimes no click is necessary for the window to become UNRESPONSIVE and all display updates stop. The loop does finish most of the time and the window becomes responsive again.

This really worries me because my app will run lots of loops and its possible that they will be large.

Why is this happening?...how do I make sure the user does not experience this?

Thank you thank you.

[makeshyft]

And as I was writing to you guys .... I had THIS experience....lol.... I hope its not an omen.

http://www.youtube.com/watch?v=rftuhODCVnA

[bn]

Tom,

what happens in tight repeat loops, especially when they are long, is they lock up the engine. This means the engine does only the repeat loops. On a Mac it does not even have the time to update the screen.

Often if you have an error in the repeat loop you cant abort the repeat loop with escape or command-period. You have to terminate Livecode from the system.

The remedy is to add a "wait 0 milliseconds with messages"." with messages" is the magic phrase here. This gives the engine room to do its housekeeping and makes the repeat loop interruptible and makes the stack responsive again. E.g you can move the stack around.

All that said I changed your script a bit to make it more efficient especially when you do high number of repeats.
I use an array and use the random number as a key of the array and put 1 into the array, so every time the same random number is generated 1 is added to the value of the key = random number. That way I can test if the number has been generated before since the value of it will be greater 1.
This has the advantage that you don't have to test a long list for an occurence of the random number. That is a lot to do for Livecode.

Currently I put the wait 0 milliseconds with messages into the conditional if a match has been found. That is also the moment of updating the screen. Less screen updating = more speed.

I took a couple of references to field values and put the into variables since those fields never change in the repeat loop.

BTW "add 1 to i" is faster than "put i + 1 into i"

for 100,000 iterations and UI update ever 10,000 and continuous update of the number of duplicates takes about 50 seconds on my machine. And the Livecode stays responsive.

Code: Select all

on mouseUp
   local i,ii,mynum
   global WholeList
   put 1 into i
   put 1 into ii
   put empty into the field "list"
   put empty into WholeList
   put empty into the field "number of matches"
   put empty into the field "counter"
   lock messages
   
   
   put field "how many possibilities" into tHowManyPossibilities
   put field "how many repeats" into tHowManyRepeats
   put field "update every" into tUpdateEvery
   
   
   put the milliseconds into tStart -- remove when done with testing speed
   // REPEAT
   
   lock screen
   repeat tHowManyRepeats
      
      // generate number and feed it as key to an array
      put random(tHowManyPossibilities) & "-" & random(tHowManyPossibilities) & "-" &  random(tHowManyPossibilities) into mynum
      
      -- here we fill an array with mynum as key and add 1 to the value of the key, the first time the value will be 1, second time (= same key = same random number) 2 etc
      add 1 to tArray[mynum]
      
      // check field update counter
      
      if  ii is tUpdateEvery then
         put i into the field "counter"
         put mynum into the field "current number"
         put 0 into ii
      else
      end if
      
      // check current number vs array, since we use mynum as key of the array
      // and add 1 to the mynum if mynum has been added before the array contains at least 2
      // that it the reason why we test for: if tArray[mynum] > 1
      
      if tArray[mynum] > 1 then
         
         put "Matched Number: " & mynum & return after tCollect
         add 1 to tCounter
         put tCollect into field "list"
         put tCounter into field "number of matches"
         unlock screen
         wait 0 milliseconds with messages -- this lets Livcode update the screen and do some housekeeping
         lock screen
      end if
      
      
      
      add 1 to i
      add 1 to ii
      --wait 0 milliseconds with messages -- this would be the place if you want to do it every time around the repeat loop
   end repeat
   
   put the milliseconds - tStart  -- remove when done with testing speed
   unlock screen
end mouseUp

Kind regards
Bernd

[bn]

Hi Tom,

very nice video, maybe you can report that to Quality Control Center...

I also found a multipede bug in LiveCode, see attached stack. (actually three)

Kind regards
Bernd

[makeshyft]

Hahahha...nice stack.

Thanks for your help, the wait command did the trick perfectly. I didn't have the most optimised code, it didn't matter....I really just wanted to see the probability of a match, to help me decide how to generate my IDs.

6.1 RC2 has UUID Generation, so thats solved for me.

Thanks a million, happy that this had a solution, now it works like a charm....I'm killing it...and no problems so far.