Parent of Target

Richard Gaskin ambassador at fourthworld.com
Thu Aug 10 15:10:11 EDT 2017


Ali Lloyd wrote:

 > Richard wrote
 >> Jacque recently showed me the speed difference between explicitly
 >> writing out the element of an object reference:
 >>
 >>    get the width of btn 1 of cd 2 of stack "MyStack"
 >>
 >> ...vs other forms like long IDs:
 >>
 >>    put the long is of btn 1 of cd 2 of stack "MyStack" into t5Obj
 >>    get teh width of tObj
 >>
 >> The latter is much slower, yet long IDs are so good to work with.
 >
 > The only reason this is true is that in the second case you are
 > resolving the object twice.

Indeed - a very poor example on my part.  Also "teh" is not a recognized 
token. :)


 > It is not true in general - the second time the long id is used it
 > will use the id cache which is constant time, whereas "button n"
 > is O(n). Try benchmarking repeated use of the stored long id vs the
 > number version, especially if the numbers are large.
 >
 > So it's horses for courses. If it's a one-shot object access then the
 > number form is faster. For repeated use, get the long id.

Sounds good, but the benefits of long ID caching have been difficult for 
me to measure.

I was exploring this a while back in response to this forum thread:
http://forums.livecode.com/viewtopic.php?f=7&t=29555

Of course object ref performance matters most when you need to traverse 
a lot of objects or refer to objects frequently, so my test attempts to 
do both:

I made a simple stack with one button containing the script below, and 
one group containing 100 buttons.

The script uses three different methods to obtain a property value from 
every object in the group, through 100 iterations, for a total of 10,000 
accesses with each method.

When I'd posted earlier the property being obtained was the short ID, 
which seems a reasonable reflection of time needed to obtain an 
arbitrary property value.

After reading your post I changed that to long ID, but see little 
difference in relative performance.

How might I measure the benefits of long ID caching?


--=================================================--
local sObjRefsA

on mouseUp
    put 100 into n
    put (the number of btns of grp 1) * n into tIterations
    --------------
    put the millisecs into t
    repeat n
       put ObjRef1() into r1
    end repeat
    put the millisecs - t into t1
    --
    put the millisecs into t
    repeat n
       put ObjRef2() into r2
    end repeat
    put the millisecs - t into t2
    ------------------
    -- Last test requires that we first obtain the object refs to
    -- measure the benefits of long ID caching:
    repeat with i = 1 to the number of btns of grp 1
       put the long id of btn i of grp 1 into sObjRefsA[i]
    end repeat
    --
    put the millisecs into t
    repeat n
       put ObjRef3() into r3
    end repeat
    put the millisecs - t into t3
    --------------------
    set the numberformat to "0.0000"
    put t1/tIterations &" - Method 1 - full expression by number " &cr \
    &   t2/tIterations &" - Method 2 - mixed expression"  &cr \
    &   t3/tIterations &" - Method 3 - long ID only" &cr \
	& (r1 = r3)
end mouseUp


-- Ordinal references all the way down:
function ObjRef1
    put the number of btns of grp 1 into tNumBtns
    repeat with x = 1 to tNumBtns
       put the long id of btn x of grp 1 of cd 1 of stack \
         "objref test" &cr after s
    end repeat
    return s
end ObjRef1


-- Mix of ordinal button with group long ID:
function ObjRef2
    put the long id of grp 1 into tGrpObj
    put the number of btns of tGrpObj into tNumBtns
    repeat with x = 1 to tNumBtns
       put the long id of btn x of tGrpObj &cr after s
    end repeat
    return s
end ObjRef2


-- Long ID:
function ObjRef3
    put the number of btns of grp 1 into tNumBtns
    repeat with x = 1 to tNumBtns
       put the long id of sObjRefsA[x] &cr after s
    end repeat
    return s
end ObjRef3



-- 
  Richard Gaskin
  Fourth World Systems
  Software Design and Development for the Desktop, Mobile, and the Web
  ____________________________________________________________________
  Ambassador at FourthWorld.com                http://www.FourthWorld.com




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