MajP
You've got your good things, and you've got mine.
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- Joined
- May 21, 2018
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As I said the VBA trig functions work in Radians not degrees. You must convert. Pass in degrees then convert inside your distance functions. Use the converted values in your function
example
The duplicates are not a big deal, until I figure out what is dragging down my implication. If I can get my array method to run as fast as your array method, then I should be able to make the KDTree much faster. In theory. As I said, I do the same method and algorithm as you show. The big difference is you use a 3 dimensions array to save ID, lat, long. I build an object called a LocationPoint. It has three properties ID, Lat, Long. My array is a one dimensioned array filled with LocationPoints. So you read the three dimensions as you loop, I read the properties inside the location point.
I believe in theory your implementation should be faster based on efficiency of memory location. I would expect that to be slightly faster not orders of magnitude faster. If that is truly the case then I do not think in VBA I can code the KDTree with any improvement since the algorithm may be faster, but the implementation using objects is not faster than an multidimensional array with a less efficient algorithm. You may be as good as you are going to get. but the implementation of the objects may not. This issue may be a shortcoming of VBA and not seen in other languages.
example
Code:
Const decToRad = 3.14159265358979 / 180
Const radiusOfEarth = 3963.1
'radiusOfEarth =3963.1 statute miles, 3443.9 nautical miles, or 6378 km
Dim radLatStart As Double
Dim radLongStart As Double
Dim radLatEnd As Double
Dim radLongEnd As Double
radLatStart = decLatStart * decToRad
radLongStart = decLongStart * decToRad
radLatEnd = decLatEnd * decToRad
radLongEnd = decLongEnd * decToRadThe duplicates are not a big deal, until I figure out what is dragging down my implication. If I can get my array method to run as fast as your array method, then I should be able to make the KDTree much faster. In theory. As I said, I do the same method and algorithm as you show. The big difference is you use a 3 dimensions array to save ID, lat, long. I build an object called a LocationPoint. It has three properties ID, Lat, Long. My array is a one dimensioned array filled with LocationPoints. So you read the three dimensions as you loop, I read the properties inside the location point.
I believe in theory your implementation should be faster based on efficiency of memory location. I would expect that to be slightly faster not orders of magnitude faster. If that is truly the case then I do not think in VBA I can code the KDTree with any improvement since the algorithm may be faster, but the implementation using objects is not faster than an multidimensional array with a less efficient algorithm. You may be as good as you are going to get. but the implementation of the objects may not. This issue may be a shortcoming of VBA and not seen in other languages.
