ChatGPT examples

[Alex Tweedly]

Fascinating. Thank you so much for that Geoff.

I've been afraid to play with ChatGPT so far - too worried abut getting 
sucked in and spending way too much time ....

I did take a look at your third example (since I can never resist a 
performance challenge :-)

There are a number of minor tweaks that could be made to improve performance

1. set initial value to infinity rather than calculating a distance 
between the first two points.

2. "number of elements in pPoints" is unvarying within any one call - so 
extract it to a variable at the start

3. use the square of the distance rather than the actual distance - save 
N**2 calls to sqrt

4. use "DX * DX" rather than "DX ^ 2" (about 25% faster)

5. calculate distance in-line rather than call a function

but those all add up to maybe 10% performance improvement (or less - I 
didn't test it). That's useful - but not enough.

For a modest number of points (2000 random points), this takes approx 
16.5 seconds !!

We need a better algorithm. If we use a "linear scan", we can change it 
from essentially Order(N**2) to approx Order(N).

Summary:

  - sort the points by X coordinate

  - while scanning the inner loop, as soon as the difference in Xcoord 
from the 'outer' point exceeds the minDist so far, you can reject not 
just this point, but all subsequent points, and hence exit the inner 
loop immediately.

This brings the time down from 16500 millisecs to 25 millisecs.

BUT - I have no clue how I'd go about describing this to ChatGPT :-)

NB I changed the input parameter to be the list of points rather than 
the array.

Code:

function closestPointsSQ pLines
    sort pLines by item 1 of each
    put pLines into pPoints
    split pPoints by CR
    put infinity into minDist
    put the number of elements in pPoints into N
    repeat with i = 1 to N-1
       repeat with j = i + 1 to N
          put item 1 of pPoints[j] - item 1 of pPoints[i] into t1
          if t1 * t1 > minDist then exit repeat
          put item 2 of pPoints[j] - item 2 of pPoints[i] into t2
          put t1 * t1 + t2 * t2 into dist
          if dist < minDist then
             put dist into minDist
             put pPoints[i] & " " & pPoints[j] into closestPoints
          else if dist = minDist then
             put return & pPoints[i] & " " & pPoints[j] after closestPoints
          end if
       end repeat
    end repeat
    return closestPoints
end closestPointsSQ

-- Alex.

On 20/01/2023 06:02, Geoff Canyon via use-livecode wrote:
> I tested three use cases, with variations, using ChatGPT for (live)code
> generation. There was a lot of back and forth. In the end, I solved all the
> problems I set, but in some cases I had to hold ChatGPT's hand pretty
> tightly.
>
> That said, I learned some things as well -- about LiveCode. ChatGPT's code
> for Fizz Buzz was faster than mine.
>
> My code was faster for reversing lines. But ChatGPT, when asked to "make
> the code faster" gave several suggestions, some of which were wrong or
> impossible, but one of them was my method, and when I said "write that
> option" it did, with only a few corrections needed.
>
> And one of the ideas, while wrong, caused me to think of a different way to
> solve the problem, and that way ended up being faster than my original
> solution by over 3x on reversing 10k lines. Getting ChatGPT to write this
> new method was *hard*.
>
> In any case, I wrote it all down in a google doc
> <https://docs.google.com/document/d/1W3j5WaFhYZaqSt0ceRQj8j160945gSwG_nyZsCBP6v4/edit?usp=sharing>.
> If you're curious, have a read. That URL is open for comments/edit
> suggestions. If you have any I'd love to hear them.
>
> Thanks!
>
> Geoff
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