[QST]Why Does CUTLASS Use 3-4-3 Swizzle?

[ziyuhuang123]

May I kindly ask why the swizzle configuration in CUTLASS is specifically set to 3, 4, and 3? I would greatly appreciate any insights or explanations regarding the rationale behind this design choice. Thank you so much in advance!

// K-major GMMA layouts in units of bits
using Layout_K_INTER_Atom_Bits  = ComposedLayout<Swizzle<0,4,3>, smem_ptr_flag, Layout<Shape<_8, _128>,Stride< _128,_1>>>;
using Layout_K_SW32_Atom_Bits   = ComposedLayout<Swizzle<1,4,3>, smem_ptr_flag, Layout<Shape<_8, _256>,Stride< _256,_1>>>;
using Layout_K_SW64_Atom_Bits   = ComposedLayout<Swizzle<2,4,3>, smem_ptr_flag, Layout<Shape<_8, _512>,Stride< _512,_1>>>;
using Layout_K_SW128_Atom_Bits  = ComposedLayout<Swizzle<3,4,3>, smem_ptr_flag, Layout<Shape<_8,_1024>,Stride<_1024,_1>>>;