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Posted: **Mon Jul 02, 2018 11:38 am**

Hi Dick,

maybe I'm lazy, but I use AAdd() every time I don't know the exact length at the start of the loop.

Maybe one could ask first for the number of records and then preallocate the array, but as we have seen there is not soo much performance penalty.

Wolfgang

Posted: **Mon Jul 02, 2018 12:11 pm**

Dick,
if you care to try Johan's code yourself, or read my observation, i'd simply stay lazy. The difference is neglectible, at least as long as you don't manipulate thousands of arrays with thousands of entries all at once...

Karl

Posted: **Mon Jul 02, 2018 12:35 pm**

Hi Dick,

ic2 wrote:Hello Johan,
lumberjack wrote: Was just mentioning it since using AAdd() in both instances or ArrayNew(), will show the performance penalty to the "lazy" programmers out there...
I'm catching up forum messages and I was intrigued by this remark. I have many places in my program where I use AAdd. E.g. we want a total of a series of general ledger accounts and for every record with a booking on a GL, we use AScan to see if we already added that GL in an array, if not, we AAdd to the GL array and the total value array.
Seems a good way to me, even AAdd is poor regarding performance.
What would the non lazy programmer do?
Dick

Ok, maybe as you catch up you will get to Wolfgang's test. Seems there is no performance penalty in X# anymore.

Posted: **Mon Jul 02, 2018 5:05 pm**

Guys, also in X# it is always better to use ArrayCreate() instead of AAdd(), when you already know the length of the array, both in speed and in GC activity/memory usage terms. Run the following with the X# runtime test twice, once for AAdd() and once for ArrayCreate()) and you will see the differences.

Having said that, very very rarely one will need to create an array of 20000000 elements!

So for "normal" usages, the difference is really negligible, so I agree it's just better to use what everyone's more comfortable with. But in case you do create long arrays in tight loops, then ArrayCreate() is much better.

Code: Select all

FUNCTION DoTest() AS VOID
	LOCAL nMemory AS INT64
	LOCAL nElements AS INT
	LOCAL dTime AS DateTime
	LOCAL lUseAAdd AS LOGIC
	LOCAL a AS ARRAY
	
	nElements := 20000000
	
	? "Press Space for AAdd() test, Return for ArrayCreate()"
	lUseAAdd := Console.ReadKey():Key == ConsoleKey.Spacebar
	? "Running test..."

	nMemory := GC.GetTotalMemory(FALSE)
	dTime := DateTime.Now
	
	IF lUseAAdd
		a := {}
		FOR LOCAL n := 1 AS INT UPTO nElements
			AAdd(a,n)
		NEXT
	ELSE
		a := ArrayCreate(DWORD(nElements))
		FOR LOCAL n := 1 AS INT UPTO nElements
			a[n] := n
		NEXT
	END IF
	
	? "Time elapsed:", (DateTime.Now - dTime):ToString()
	? "Memory currently used (after possible collections):", (GC.GetTotalMemory(FALSE) - nMemory):ToString("###,###,###,### bytes")
	? "The GC was invoked", GC.CollectionCount(0), "times"
	
	WAIT
	GC.KeepAlive(a)

RETURN

FUNCTION Start( ) AS VOID
	DoTest()
RETURN

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