[swift-users] Design and performance of Vector2/3/4 and Matrix

David Turnbull dturnbull at gmail.com
Fri Dec 18 23:19:17 CST 2015

On Fri, Dec 18, 2015 at 4:34 PM, Janosch Hildebrand <jnosh at jnosh.com> wrote:

> If you only care about having a simple cross-platform library, doing a
> simple implementation by yourself is fine. Also Swift (well, LLVM) is also
> pretty good at auto-vectorization so you get decent results for custom
> vector/matrix types.
> However OpenGL-related code is usually pretty performance sensitive and
> the math parts doubly so, so I'd recommend wrapping some appropriate
> libraries instead of writing your own...

Multiplying two mat4x4 is one of the most complex and common operations.
Doing 2 million of these...

C++: 1.3 seconds
Swift: 1.9 seconds

The C++ code is glm using packed SIMD operations. Swift is just plain
whatever LLVM gave me with -O.

While implementing the multiplication I darn near fell out of my chair when
the compiler said, "Expression was too complex to be solved in reasonable
time; consider breaking up the expression into distinct sub-expressions." I
had to break it in half twice before the compiler stopped complaining about
the math being too hard.

-david (https://github.com/AE9RB/SwiftGL)
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