| I expected that appending items to a list by setting (or copying to) the end of a list would be fairly efficient, but found it's not. It appears that the process grows with the size of a list, so that the time involved grows exponentially, at least with the ways I've tried so far. For instance, creating a list as follows take about 1 second for 500 loop iterations, 4 seconds for 1000, and 32 seconds for 2000:
set startTime to (time of (current date)) set theList1 to {} set timeStamp to 0 repeat with idx from 1 to 2000 set end of theList1 to {timeStamp, noteOn, 60, 100} set end of theList1 to {timeStamp + 1, noteOn, 60, 0} set timeStamp to timeStamp + 1 end repeat (time of (current date)) - startTime
If I split the job up, working in smaller chunks and concatenating them, performance goes up dramatically. For instance, I can do the same job in a second if I nest two loops, with the inner one building a smaller section and the outer loop concatenating the result into another list. Obviously, that's worth is, since the code only grows by a couple of lines and executes 32 times faster, but it seems like there should be a better way. Surely there must be an efficient way to append something to the end of a long list--am I missing something?
Thanks |