LUCY! You have some 'splainin' to do!

[GEOSoft]

I was just working at re-writing a function and I noticed something that made no sence so I whipped up a test script to check the time differences.

Here is the test script using a large file.

$sFile = "wordlist.txt"
$Time1 = 0
$Time2 = 0
$iLoops = 200
For $i = 1 To $iLoops
    $Time1 += _Time1()
Next

For $i = 1 To $iLoops
    $Time2 += _Time2()
Next
ConsoleWrite("Average Read Only: " & Round(($Time1/$iLoops)/1000, 5) & "Seconds" & @CRLF)
ConsoleWrite("Average Open/Read/Close: " & Round(($Time2/$iLoops)/1000, 5) & "Seconds" & @CRLF)

Func _Time1()
    Local $iTime = 0;; Just to be safe lets flush the timer
    $iTime = TimerInit()
    FileRead($sFile)
    Return TimerDiff($iTime)
EndFunc

Func _Time2()
    Local $iTime = 0;; Just to be safe lets flush the timer
    $iTime = TimerInit()
    $hFile = FileOpen($sFile)
    FileRead($hFile)
    FileClose($hFile)
    Return TimerDiff($iTime)
EndFunc

If I run that script 10 or so times the returns will differ but that's not the issue. 9 out of 10 times FileOpen/Read/Close() will be faster than a simple FileRead() and that makes no sense to me. I even restarted my system to see if File cache was coming into play and it doesn't appear to be.

You can use any file but to test it with the one I used you can download it here

http://dundats.mvps.org/autoit/files/wordlist.zip

Would someone like to hazard a guess as to why a simple FileRead is slower?

Edited June 8, 2011 by GEOSoft

[ProgAndy]

A FileRead without FileOpen/Close has to call FileOpen and FileClose internally, so they should need about the same time.

[GEOSoft]

I had forgotten that part but in most tests using FileOpen/Read/Close() was faster and that makes no sense to me at all. I should also mention that changing the value of $iLoops can vary the results by a considerable amount. That is considerable as in milliseconds which is not really a large amount.

[BrewManNH]

I saw the same results as you GEOSoft when I ran it from my hard drive. When I ran it from a thumb drive I saw the opposite results in that FileOpen was faster by a few milliseconds. Even though, both scenarios ran in comparable timeframes regardless of which drive it was being run on.

[GEOSoft]

I can see drive read speeds making a difference and I'm actually running it from my slowest drive which is also my largest drive.

The way I see it is even though using a simple FileRead() makes internal calls for FileOpen and FileClose those I would think are API calls so they should be faster.

Maybe a dev will come along and shed some light on this.

[Valik]

Swap the order of the tests. Do the results change?

[GEOSoft]

Not for me. I'll try again after my next restart and see what I get then. I have a suspicion that file caching is coming into play somehow.

[GEOSoft]

Okay, todays tests show that no matter what order I call the functions; FileOpen/Read?Close is still faster although the actual times did change by a very slight amount.

First test was _Time1() first followed by a test with _Time2() first

Then a reboot of the system

Tested _Time2() first followed by a test with _Time1()first

Then a reboot into Win 7 and repeat the tests

Same results as under Vista although the times were slightly better in 7 which has been pretty much the norm for W7 on this system anyway probably because it doesn't have a lot of crap installs that my Vista does. I didn't bother testing under XP at all. I was seeing slightly larger differences yesterday and I still think part of the discrepancy is File Cache related.

Here are the actual values

Average Read Only: 0.04251Seconds Test 1 = timer 1 first

Average Open/Read/Close: 0.04322Seconds

Average Read Only: 0.04248Seconds Test 2 = timer 2 first

Average Open/Read/Close: 0.04245Seconds

After reboot -- Vista

Average Read Only: 0.0423Seconds Test 3 = timer 2 first

Average Open/Read/Close: 0.04215Seconds

Average Read Only: 0.04195Seconds Test 4 = timer 1 first

Average Open/Read/Close: 0.04199Seconds

After Reboot Win 7

Average Read Only: 0.04142Seconds Test 5 = timer 1 first

Average Open/Read/Close: 0.0411Seconds

Average Read Only: 0.04134Seconds Test 6 = timer 2 first

Average Open/Read/Close: 0.04187Seconds

[guinness]

I got the same results on Win 7 x64. I use FileOpen/FileRead in most of my applications anyway.

[GEOSoft]

I just can't figure out why using 3 calls to AutoIt functions should be faster than using a single AutoIt function call which I assume internally makes the required API calls. If indeed thay are API calls; and Valik didn't clarify that point in his reply.

This is more for curiosity anyway since I do know that what I was attempting to do with the UDF I was looking at would be much slower than it is now anyway and that is not because of these time differences either.

[Valik]

It all goes through a class Jon wrote in either case. I'm not sure why the results are so close.