[mkgmap-dev] [Patch v3] LocationHook with new Quadtree

Thu Jan 12 21:41:05 GMT 2012

Hi WanMil,

thanks for the quick response.

> some ideas and questions:
> 
> * BoundaryQuadTree.Node.add always performs a costly intersect of the 
> area, also if the area is completely within the bbox. Maybe it's better 
> first to check if the bbox contains the area (or area.getBounds()).
Good point. I'll try that.

> 
> * I don't understand the following part in Node.add:
> ---
> // optimization: don't add equal areas, only add the tags
> // we test only against the last element because that is likely
> // to match
> if (numNodes > 0 && a.equals(nodes.get(numNodes-1))){
>    addMissingTags(nodes.get(numNodes-1).tags, bTags);
>    return;
> }
> ---
> a is an area and nodes.get returns a NodeElem so equals will always be 
> false.
> I think you want to compare to nodes.get(..).area but I do not 
> understand that either. Why should two areas be equal?

argh! This error was introduced while I cleaned the code :-(
Of course I want to compare the areas. We add all boundaries to the tree, even those with level=2. 
Since the boundary list is sorted so that they appear last, it is very likely that the area completely 
covers the bbox of the tree. In this case the area will be the bbox. 

> 
> * LocationHook.mkgmapTagsArray starts with an empty string element. I 
> don't like that.
> 
> * for (int i = 12; i >= 1; --i){
> 	if (elem.getTag(mkgmapTagsArray[i] ) != null)
> 		res |= (1 << i);
> }
> 
> =>
> 
> for (int i = 0; i mkgmapTagsArray.length; i++) {
> 	if (elem.getTag(mkgmapTagsArray[i] ) != null)
> 		res |= (1 << i);
> }
> 
> Counting down is quite unusual and should only be done if there is a 
> real reason for it.

You are right, there is no longer a reason for it. I'll change that. I used this loop together 
with a bitmask and a call to Integer.highestOneBit()

> 
> * I don't understand why you need a merge() method. Could you explain 
> what you are doing in this method and why it's required?
The get method() of the tree returns the data for the first area that contains the coord. 
This area should contain all tags of the area itself plus those from areas intersecting it. 
Maybe this is not correct?

Ciao,
Gerd

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