[AccessD] Timer etc.

[Arthur Fuller]

I made the changes to the data types as you suggested, Stuart, and it
brought the times much closer together.
While: 182.7031
For: 192.3081

That's still with 1 million iterations.

On Tue, Sep 27, 2022 at 7:07 PM Arthur Fuller <fuller.artful at gmail.com>
wrote:

> Thanks, Stuart. I'll make those changes.
>
> On Tue, Sep 27, 2022 at 5:34 PM Stuart McLachlan <stuart at lexacorp.com.pg>
> wrote:
>
>> That result should have gone without saying.
>>
>> The For...Next loop just required incrementing or decremeing a Register
>> Variable,
>> comparing it to a constant and jumping
>> INC     EDX
>> CMP     EDX, 1000000
>> JLE     LP1
>> That may well be optimised by a good compilerby loading EDX with
>> 100000  and then just two instructions:
>> DEC   EDX
>> JNE   LP1
>>
>> The While...Wend loop will have several extra steps to perform: with the
>> variable  i -
>> moving it in and out of registers, both when  incrementing  it and when
>> comparing it to
>> 1000000.
>>
>> As a side note, rounding Timer by declaring it as LONG is a strange thing
>> to do. If you'd
>> made it double or single , you could have got meaningful relative
>> difference results in a
>> fraction of a second with far fewer iterations.
>>
>>
>> On 27 Sep 2022 at 12:09, Arthur Fuller wrote:
>>
>> > A few messages ago, I asked for advice on resolving times. Gustav and
>> > JWC (Colby) replied, and I got what I needed.
>> >
>> > I'm teaching myself C++, and came across some code, which I decided to
>> > port to VBA with modifications. The point of the exercise was to
>> > compare the performance of a While Loop and a For/Next loop. On a
>> > small scale, the differences are unnoticable, so I upped the iteration
>> > count to one million. Then the difference is dramatic. The While test
>> > took 612 seconds; the For/Next loop took 190 seconds.
>> >
>> > In case anyone is interested, here is the code:
>> >
>> > <code>
>> > Option Explicit
>> >
>> > Const CON_Limit = 1000000
>> >
>> > Function WhileLoopTest()
>> >     Dim i As Long
>> >     i = 1
>> >     Dim timStart As Long, timStop As Long
>> >     timStart = Timer
>> >     'Debug.Print timStart
>> >     While i <= CON_Limit
>> >         Debug.Print i
>> >         i = i + 1
>> >     Wend
>> >     timStop = Timer
>> >     'Debug.Print timStop
>> >     'MsgBox "Elapsed time for " & CON_Limit & " iterations" & vbCrLf &
>> >     _ '    (timStop - timStart) & " seconds.", vbOKOnly, "While Test"
>> >     WhileLoopTest = (timStop - timStart)
>> > End Function
>> >
>> > Function ForNextTest()
>> >     Dim i As Long
>> >     i = 1
>> >     Dim timStart As Long, timStop As Long
>> >     timStart = Timer
>> >     'Debug.Print "Start: " & timStart
>> >     For i = 1 To CON_Limit
>> >         Debug.Print i
>> >     Next
>> >     timStop = Timer
>> >     Debug.Print "Stop: " & timStop
>> >     'MsgBox "Elapsed time for " & CON_Limit & " iterations" & vbCrLf &
>> >     _ '    (timStop - timStart) & " seconds.", vbOKOnly, "For/Next
>> >     Test" ForNextTest = (timStop - timStart)
>> >
>> > End Function
>> >
>> > Sub DurationTest()
>> >     MsgBox "This program compares While loops with For/Next loops",
>> > vbOKOnly + vbInformation, _
>> >     "Timing Test"
>> >     Dim TimeW As Currency, TimeF As Currency
>> >     TimeW = WhileLoopTest()
>> >     TimeF = ForNextTest()
>> >     MsgBox "Results of comparison for " & CON_Limit & " iterations:" &
>> > vbCrLf & _
>> >         "While Loop: " & TimeW & " seconds." & vbCrLf & _
>> >         "For/Next  : " & TimeF & " seconds.", _
>> >         vbOKOnly + vbInformation, _
>> >         "While v. For/Next Comparison"
>> > End Sub
>> > </code>
>> >
>> > --
>> > Arthur
>> > --
>> > AccessD mailing list
>> > AccessD at databaseadvisors.com
>> > https://databaseadvisors.com/mailman/listinfo/accessd
>> > Website: http://www.databaseadvisors.com
>> >
>>
>>
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>
>
> --
> Arthur
>
>

-- 
Arthur