Android Question Performance List v/s Map

[nikolaus]

Hi, Wyken Seagrave writes in his B4A book that reading (and writing?) an item from a Map is much faster than from an Array.

How about Lists? Are they rather Maps with fixed keys (Indices) or Arrays with dynamic size?

Does it make sense to feed larger ListViews (about 100 to 200 lines) fom a Map with index-numbers as keys rather than from a List?

Thx
Nikolaus

 

[DonManfred]

    Dim dtstart, dtend As Long
    Dim total As Period
    Dim testlist As List
    testlist.Initialize
    For i = 0 To 500000
        testlist.Add("Line "&i)
    Next
    dtstart = DateTime.Now
    lv.Clear
    For i = 0 To testlist.Size-1
        lv.AddSingleLine(testlist.Get(i))
    Next
    dtend = DateTime.Now
    total = DateUtils.PeriodBetween(dtstart,dtend) 
    Log("Difflist="&total.Hours&":"&total.Minutes&":"&total.Seconds&".")
 
    lv.Clear
    Dim testmap As Map
    testmap.Initialize
    For i = 0 To 500000
        testmap.Put(i,"Line "&i)
    Next
    dtstart = DateTime.Now
    lv.Clear
    For i = 0 To testmap.Size-1
        lv.AddSingleLine(testmap.Get(i))
    Next
    dtend = DateTime.Now
    total = DateUtils.PeriodBetween(dtstart,dtend) 
    Log("Diffmap="&total.Hours&":"&total.Minutes&":"&total.Seconds&".")

Filling 500.000 items to a LIST and put them in a listview needs 6 seconds on my device.
Filling 500.000 items to a map and put them in a listview needs 4 seconds on my device.

I would say using a MAP is faster but i dont think that on 100 to 1000 items should make no real difference in time... with such less amount of items you can use what you want i suppose

 

[stevel05]

If you are using a list and feel it's slow, then test it with a map and measure the difference. I have an app that builds a listview from a list with > 2000 entries and rebuilds it in real-time filtering the original list. The performance is very good.

 

[DonManfred]

With a map it should be 1 ms faster, @stevel05
But i´m with you... With 0 to 1000 Items it should make no difference

 

[stevel05]

That's not enough time to make a cup of coffee

 

[DonManfred]

With B4A as Development-Environment you dont have time for anything cause it is so fast...
I suggest to get the coffee intravenously

 

[stevel05]

With B4A as Development-Environment you dont have time for anything cause it is so fast...

That's very true, I just wish I could design faster

 

[nikolaus]

Thanks Manfred for evaluating this.

Seagrave writes using a Map is very fast compared to an Array, that's why I was asking. A performance ratio of 2:3 is far away from that.

 

[sagyrd]

I have notice low performance of a Map,when exchanging data between Activities.
Example:
'Activity1
Sub Process_Globals
Dim Cache as Map
End Sub
'Activity2
Activity1.Cache.Get("whatever")

Copying map solves this problem :
Cache = Activity1.Cache

 

[Erel]

There is no difference between "copying" the map to referencing it directly.

You aren't really copying the map. You've just created another reference to the same object.

Also note that it doesn't matter where the process global variable is declared.

 

[sagyrd]

I see you point, but creating this reference instead of accessing it directly improves performance a lot

 

[Erel]

Can you post a small project that demonstrates it?

 

[sagyrd]

I have to apology here.
I have created a small project like you asked and I can't recreate this issue.
The project contains very same files and doing exactly the same what my original code is doing. The only difference is that instead of using list of files, I was iterating through sql query result.
In both project performance is very good right now. I have detailed tested it yesterday(I was logging time of every action, and definitely performance drop was until accessing map ) and without creating references, performance was very low (it took about 5 seconds to load images) and I'm 100% sure that the delay was caused when I was accessing map directly (Activity1.Cache). After creating a reference, the speed increased drastically to the current level(few 'ticks').
I'm using Samsung Galaxy Tab 3 Lite for debugging. Maybe this issue shows up when device memory is full ?

 

[Erel]

There isn't any difference between a process global variable declared in another module and a variable declared in this module.

The result will be exactly the same.