Atan2 in my App and possible speeding it all up.

[Langy]

To cut a long story short I'm trying to make an app that has to ready anything from 1 to a vast number of XML files from a website. I started out in vb.net (not used it much but can often muddle through apps) found that too complicated for what I wanted, then Excel but it hung every time after about 5 downloads of XML files.

So I've come to AutoIT as I use it for a fair bit of scripting to modify settings on our users computers.

One of the things I need to do in my app is read in around 6000 sites in one XML file, the user chooses one and then I need to calculate the distance and direction from the selected site for all the rest. Now those 6000 sites only really have to be loaded once as I will end up making a new XML file only storing the sites the users select.

Now when I try to load all 6000 sites to start with in the code below it starts off really quick as I can monitor it with GUICtrlSetData($lblStatus2,UBound($Sites,1)) reporting back to my splash screen. However as time goes on the records take longer and longer to get through. The whole process takes about 2 minutes. So any assistance on speeding that up would be great. Basically I need to load the sites into an array which I can then use to create a list view based on a users search criteria.

For $oLocations In $oXML.selectNodes("/Locations")
      $sDirRefID = $oLocations.getAttribute("id")
      For $oSite In $oLocations.selectNodes("Location")
         $Sites[UBound($Sites,1)-1][0] = $oSite.getAttribute("id")
         $Sites[UBound($Sites,1)-1][1] = $oSite.getAttribute("name")
         $Sites[UBound($Sites,1)-1][2] = $oSite.getAttribute("latitude")
         $Sites[UBound($Sites,1)-1][3] = $oSite.getAttribute("longitude")
         $Sites[UBound($Sites,1)-1][4] = $oSite.getAttribute("elevation")
         $Sites[UBound($Sites,1)-1][5] = $oSite.getAttribute("region")
         $Sites[UBound($Sites,1)-1][6] = $oSite.getAttribute("unitaryAuthArea")
         $Sites[UBound($Sites,1)-1][7] = $oSite.getAttribute("nationalPark")
         
         If Int(UBound($Sites,1)/100) = UBound($Sites,1)/100 Then
            GUICtrlSetData($lblStatus2,UBound($Sites,1))
         EndIf
                 
         ReDim $Sites[UBound($Sites,1)+1][10]

      Next
   Next

So my next dilema which I spent several hours on today was to work out the distance and direction between the sites. That took me a few hours in Excel to start with and converting the distance to AutoIT was quite easy as in the code below.

Func Distance($LatD,$LongD)

   $HomeLat = 54.9425
   $HomeLong = -2.7349

   $rad1 = _Radian(90-$HomeLat)
   $cos1 = Cos($rad1)
   $sin1 = Sin($rad1)

   $DISTANCE = ACos(Cos(_Radian(90-$HomeLat))*Cos(_Radian(90-$LatD))+Sin(_Radian(90-$HomeLat))*Sin(_Radian(90-$LatD))*Cos(_Radian($HomeLong-$LongD)))*6371

   Return $DISTANCE

EndFunc

The next thing was the direction. I got a nice script running at work using the _Atlan2 code that was in math.au3. However I've installed a newer version of AutoIT at home on my laptop and went to run the code tonight only to find the _Atlan2 has been removed. So some hunting around on actual equations and I've come up with below to replace it. Any thoughts on this from anyone most appreciated.

Func Direction($LatD,$LongD)

   $HomeLat = 54.9425
   $HomeLong = -2.7349

   $y = $HomeLat - $LatD
   $x = $HomeLong - $LongD
   $bear = ATan2($y,$x)
   $degB = 180 + _Degree($bear)

   Return $degB

EndFunc

Func ATan2($x, $y)
   Local Const $PI = 3.14159265358979
   If $x > 0 Then
      Return ATan($y / $x)
   ElseIf $x < 0 Then
      Return ATan($y / $x) - _Radian(180)
   ElseIf $x = 0 Then
      If $y > 0 Then
         Return 90
      ElseIf $y < 0 Then
         Return -90
      ElseIf $y=0 Then
         Return 0
      EndIf
   Else
      MsgBox( 16, "Error - Division by zero", "Domain Error in Function: ATan2()" & @LF & "$x and $y cannot both equal zero" )
      SetError( 1 )
   EndIf
 EndFunc

I'm not a newbie, but can get most basic programming done in vb, vba, asp, asp.net and AutoIT to name a few. I may not set the procedures out like hardcore programmers, but it works and always willing to learn. I find that you learn more when faced with problems like this where you have to find an answer.

Thanks in advance for any assistance.

[Bowmore]

This should solve your first problem, the slow load. ReDim is a slow function so it's best to not use it every time you add a new record. Add new array space in big blocks and remove any unused rows when you have finished loading.  

Local $iSite = 0
   Local $Sites[5000][10] ;Make the array big enough to hold the estimated number of rows
   $iSitesMaxIdx = UBound($Sites,1)-1 ; save the size of array so you don't have to call UBound all the time
   
   For $oLocations In $oXML.selectNodes("/Locations")
      $sDirRefID = $oLocations.getAttribute("id")
      For $oSite In $oLocations.selectNodes("Location")
         $Sites[$iSite][0] = $oSite.getAttribute("id")
         $Sites[$iSite][1] = $oSite.getAttribute("name")
         $Sites[$iSite][2] = $oSite.getAttribute("latitude")
         $Sites[$iSite][3] = $oSite.getAttribute("longitude")
         $Sites[$iSite][4] = $oSite.getAttribute("elevation")
         $Sites[$iSite][5] = $oSite.getAttribute("region")
         $Sites[$iSite][6] = $oSite.getAttribute("unitaryAuthArea")
         $Sites[$iSite][7] = $oSite.getAttribute("nationalPark")
             
         If Int($iSite/100) = $iSite/100 Then
            GUICtrlSetData($lblStatus2,$iSite)
         EndIf
        if $iSitesMax = $iSitesMaxIdx Then
            ;if array is full 
            ;add another 1000 rows
            $iSitesMaxIdx += 1000
            ReDim $Sites[$iSitesMaxIdx][10]
        EndIf
        ;ncrement array index
        $iSite += 1
      Next
  Next
 
 ;remove unused rows
  ReDim $Sites[$iSite][10]

[czardas]

Here's the old _ATan2() code by Nutster, in case you don't have it. I don't know why it would have been removed.

<REMOVED>

;

Edited February 23, 2014 by czardas

[Langy]

 

This should solve your first problem, the slow load. ReDim is a slow function so it's best to not use it every time you add a new record. Add new array space in big blocks and remove any unused rows when you have finished loading.  

 

Thanks that helped enormously, now the whole 6000 sites loads in a couple of seconds. I do start off now with an array at 6000 and if that fills up add 100 at a time, just in case it should ever increase. Then I finally just cut it back to size when the whole xml file is loaded.

czardas, yes I could have copied the code from my machine at work, but I think that there is an issue with it as to why it was removed. I did have to modify my code a little as it could return a negative direction. I've based my code on some proper equations I found online which should cut out any errors, plus I've tested quite a few results as to that which I have in an Excel file.

Func GeoDir($LatStart,$LongStart,$LatEnd,$LongEnd)

   $y = $LatStart - $LatEnd
   $x = $LongStart - $LongEnd
   $bear = ATan2($y,$x)
   $degB = 180 + _Degree($bear)
   If $degb < 0 Then
      $degb = 360 + $degb
   EndIf

   Return $degB

EndFunc

[czardas]

Ah, I remember reading something about this now.

Edited February 23, 2014 by czardas