Performance advantage for SIMD?

Performance advantage for SIMD?

What sort of performance increase is generally seen from enabling SIMD?  Obviously I know it will vary from project to project, but what sort of range are we talking about?  5%?  10%?  50%?  100% (in terms of processor time to solve the step)?

I'm currently using the evaluation version to develop a game, but it is fairly physics heavy.  If SIMD is a fairly noticeable increase in performance, then I guess it would be worth my while inquiring about the Budget-based License sooner rather than later.

Edit: I had read outdated information that SIMD wasn't avaliable for the free downloads, but I can see it listed, so I'm just going to try it.

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Hi Mehwoot,

It's difficult to predict what difference SIMD will make for your performance until you try it.  It makes the most difference in math intensive operations like raycasting, so if that's where a lot of your performance is going you may see an improvement.  In the best case, for operations that can be fully SIMD optimized you may be able to get up to a 4x speed up, but SIMD and non-SIMD math operations are completely separate code paths, so it's not an apples to apples comparison.

Do you mind telling me where you found the outdated infromation about SIMD not being available in the free Havok packages?  I'd like to bring it up-to-date if possible.


Josh S. Havok Developer Support Engineer

I was going off the forum posts at and

I'm afraid that Havok PcXs does not support SIMD. SIMD support is available only to fully-licensed customers.

I can't speak to future releases, but, unfortunately, PC XS is currently (and has historically been) offered as a non-SIMD package - full SIMD-enabled Havok is only available through a full commercial license.

Addtionally, if you look at hkconfigsimd.h in the free download, it says:

# if defined (HK_PLATFORM_X64) || defined(HK_PLATFORM_SIM)
# else
// x86
# endif

Since the only download is for Win32, I don't see how SIMD could possibly be enabled.

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