The motivation for multidimensional CUDA block grid

Question

I have basically the same question as posed in this discussion. In particular I want to refer to this final response:

I think there are two different que

Answer 1

There is definitely a benefit in the use of multi-dimensional grid. The different entries (tid, ctaid) are read-only variables visible as special registers. See PTX ISA

PTX includes a number of predefined, read-only variables, which are visible as special registers and accessed through mov or cvt instructions. The special registers are:

 %tid
 %ntid
 %laneid
 %warpid
 %nwarpid
 %ctaid
 %nctaid

If some of this data may be used without further processing, not-only you may gain arithmetic instructions - potentially at each indexing step of multi-dimension data, but more importantly you are saving registers which is a very scarce resource on any hardware.