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by tychver 3163 days ago
The whole Ruby VM only takes ~50ms to start, so that sounds a bit slow. I wrote a quick version in Ruby and it only takes 5ms: https://gist.github.com/jamatthews/d910a2b39c87a871264dd31d1...
1 comments
hasenj 3162 days ago
It's a bit more complicated. I'm measuring geographical distances so I'm using haversine

    from math import radians, cos, sin, asin, sqrt
    def distance(lat1: float, lon1: float, lat2: float, lon2: float) -> float:
        # taken from: https://stackoverflow.com/a/4913653/35364
        # convert decimal degrees to radians
        lon1 = radians(lon1)
        lon2 = radians(lon2)
        lat1 = radians(lat1)
        lat2 = radians(lat2)
        # haversine formula
        dlon = lon2 - lon1
        dlat = lat2 - lat1
        a = sin(dlat/2)**2 + cos(lat1) * cos(lat2) * sin(dlon/2)**2
        c = 2 * asin(sqrt(a))
        r = 6371008 # Average radius of earth in meters
        return c * r
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tychver 3160 days ago
Using Haversine distance increases it to only 13ms. I'm not sure why your Python implementation is so slow? In the real world, things like haversine are implemented as C extensions, so I wrote one for Ruby as a comparison and it runs in 3.8ms for 16k points. https://gist.github.com/jamatthews/d910a2b39c87a871264dd31d1...

The Ruby GIS libaries already have C implementations for haversine but I just wanted to show how easy it is to hook out to a C function for math heavy stuff.

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hasenj 3156 days ago
It was slow because at first I put the import inside the function. Moving it out improved the python performance to 20ms (as I mentioned in another comment).

The javascript version runs in 15ms.

> In the real world, things like haversine are implemented as C extensions

Having to write C-extensions is, well a point of friction, and adds complexity.

If you just used a native language to begin with, the simple straight forward code would work just fine.

Btw the source is here, and it also includes the csv file. https://bitbucket.org/hasenj/geodb/src

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tychver 3156 days ago
Yeah, that'll do it!

C extensions are a core part of Ruby. A big chunk of the std lib is implemented in C. You shouldn't be afraid of writing a tiny bit of C. Ruby and Python are scripting languages. They're literally designed for scripting another language.

The JIT for Ruby 3 is well underway, so in a bit it'll be a complete non-issue anyway.

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