which is faster? [repeat loop]

[Jellobus]

Hello,

1. Which code is faster?
2. which code sorts lines more randomly? or will they have a same effect?

This sort lines by random(3) repeating 5 times.

Code: Select all

on mouseUp
  repeat 5
     sort lines of field "lines" by random(3)
  end repeat
end mouseUp

or

And this one sorts lines by random 15 (= 5x3)

Code: Select all

on mouseUp
   sort lines of field "lines" by random(15)
end mouseUp

Thanks in advance!

Louis

[bogs]

Interesting question. The way I'd look at it is something like this (not tested psuedo code)

Code: Select all

on mouseUp
  put the seconds into tmpStartTime
  repeat 5
     sort lines of field "lines" by random(3)
  end repeat
  answer (tmpStartTime - the seconds)
end mouseUp

I'm sure I mangled that somewhere, but I'm just as sure you get the drift It will probably occur in less than a second, most likely in the milliseconds range, so adjust for that.

[dunbarx]

One thing.

It is irrelevant to time such gadgetry in a field. That is orders of magnitude slower than doing so in a variable. ALWAYS:

Code: Select all

put the field into a variable
do stuff to the variable
put the variable back into the field

Beyond that, I would increase the number of repeat dramatically, like five orders of magnitude, or you might get virtually zero with both trials.

Of course, going back to my original point, if you hobble the process by working directly with a field, you might actually get results that are above zero. But that is hardly a rationale.

Craig Newman

[SparkOut]

Sorting 5 times will be, er, 5 times slower than sorting once, won't it? (Whether that's a detectable amount or not.)
I don't think sorting by random(3) means 5 times less "random" than by random(15).
Personally I would put the field into a variable, as Craig says. Then (just once)

sort lines of tVar by random(the number of lines in tVar)

[bogs]

It is irrelevant to time such gadgetry in a field. That is orders of magnitude slower than doing so in a variable. ALWAYS:

I absolutely agree with this statement, but it isn't like the universe will implode if you don't

Personally I would put the field into a variable, as Craig says. Then (just once)
sort lines of tVar by random(the number of lines in tVar)

Now this brings up an interesting thought. I thought random wasn't truly random (i.e. you always get the same sort for the first random), but I could be wrong there. If it isn't truly random then wouldn't you need to sort it a minimum of 2 times, or seed it or something?

[SparkOut]

Can you explain "the same sort for the first random" please?

I believed random would take a seed from the current memory address. Which should produce a random enough result for most purposes, and afaik would be just as random as the second or third, unless specific seeding practices are undertaken?

[bogs]

Can you explain "the same sort for the first random" please?

Well, thats my take after reading the dictionary (words emphasized by myself).

Use the randomSeed property to ensure greater randomness when generating random numbers.
Value:
The randomSeed property is an integer.
Comments:
Changing the randomSeed property changes the pseudorandom numbers generated by the random function and used by the any keyword. Using the same seed creates the same sequence of pseudorandom values.
For example, if you call the random function five times to generate a list of five numbers, then change the randomSeed to another value, the next five calls to the random function will produce a different list of five numbers. However, if you set the randomSeed back to its original value and call the random function five more times, the list of five numbers is the same as the first list you generated.

LiveCode uses a new randomSeed every time the application is started up.

[SparkOut]

Yes, I think that means that if you specifically set a seed value, and always use that seed value then the pseudo-random results will always be taken from that basis. If you set no seed value at all, the random function seeds itself with a pseudo-random value. I could be completely wrong though. I will have to have a play with this later to see if I can understand/decipher more, when I can get to a computer to do it on.

[bogs]

That could be too. I seem to remember playing with random by itself, then creating a randomseed that alternated for each run, but my memory ain't the best anymore (worse than usual).

*Edit - oh yah, I was thinking of this one doh

randomSort.livecode.zip

Click and hold down on the card, release to see it randomize...

(951 Bytes) Downloaded 160 times

[FourthWorld]

Yes, using the same randomSeed will produce the same psuedo-random sequence. I've used this once when writing an encryption function back before LC offered industry-standard encryption, allowing me to XOR bytes seemingly randomly but reproducibly, so that same sequence could be used to decrypt.

FWIW most computing "random" is less random than true random, as true random allows for the possibility of repeating the same sequence but computing psuedo-random algos like LC's are written to favor variety.

And then there's the larger question of whether random really exists in the natural world at all, or is merely a construct of the human mind, like a perfect circle.

[bogs]

FWIW most computing "random" is less random than true random, as true random allows for the possibility of repeating the same sequence but computing psuedo-random algos like LC's are written to favor variety.

Yeah, I seem to remember this same type of thing from other languages I've used (basics, delphi, etc)

[SparkOut]

And what really is random? Most people would question a random algo that produced a sort "1,2,3,4,5,6". Or, put another way, who would pick 1,2,3,4,5,6 for the lottery numbers? But it's just as likely as any other sequence.

[bogs]

Pretty good discussion on random here. For those of us with shorter attention spans, maybe this one.

And what really is random?

Well, I've always gone by this definition from Wikipedia (forget where I first came across it though).

Randomness is the lack of pattern or predictability in events.[1] A random sequence of events, symbols or steps has no order and does not follow an intelligible pattern or combination. Individual random events are by definition unpredictable, but in many cases the frequency of different outcomes over a large number of events (or "trials") is predictable. For example, when throwing two dice, the outcome of any particular roll is unpredictable, but a sum of 7 will occur twice as often as 4. In this view, randomness is a measure of uncertainty of an outcome, rather than haphazardness, and applies to concepts of chance, probability, and information entropy.

I suppose it ultimately comes down to what you need to get done before entropy enters the picture.

*Edit - I should have also said that generating a somewhat randomSeed should be pretty simple, such as putting the 'seconds' (which should be changing all the time) into a variable and using that (or some base of that) as the seed.

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repeat 1000 times
 put the milliseconds & cr after tmpSecs
wait 1 milliseconds
 end repeat
 put tmpSecs

Result -

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For almost anything, that should be enough randomSeed integers, using them in random

[FourthWorld]

The engine sets its own randomSeed on startup, which IIRC is also based on current clock time. A scripter will only benefit from setting the randomSeed if they want to create a reproducible series of psuedo-random sequences. For psuedo-random sequences that vary across sessions, just leave it alone and it'll do that by itself, because the clock value used for the seed will be different each time.

Back to the OP, a single random sort should suffice, as suggested earlier. I can't imagine multiple sorts will improve the seeming randomness of it.

[Jellobus]

That's enough discussion to understand this concept. Thanks a lot for all!