In a previous post SIMD Matters I discussed the big wins I got from graph coloring to make the contact solver faster. That same approach exists in Box3D. I like to call this approach “wide SIMD”. The idea is to process multiple work units at the same time. In the contact solver this means solving four contact points at the same time. This is different from “narrow SIMD” where a 3-vector (xyz) is put into a SIMD register and then standard vector math is expressed as SIMD intrinsics.