cancel
Showing results for 
Search instead for 
Did you mean: 

OpenCL

tzachi_cohen
Staff
Staff

Re: GCN SIMD vs SIMT

Jump to solution

Hi ,

GCN GPUs are strict SIMT.

Decorating a kernel with '__attribute__((vec_type_hint(<type>)))' will not influence GPU compilation artifacts.

Since GCN is a scalar architecture, i.e. each thread can at most execute a single component ALU operation in a cycle there is no point in trying to horizontally-vectorize the code.


Tzachi


savage309
Adept I

Re: GCN SIMD vs SIMT

Jump to solution

Thank you so much.

Just one more question - if I have to do a lot of transcedental functions over different data fields should I create my own ones (using polonomials that are close to the real ones), if I dont' care so much about the error ?

In other words, is it true that only the scalar unit can do transcedental functions ?

0 Kudos
Reply
tzachi_cohen
Staff
Staff

Re: GCN SIMD vs SIMT

Jump to solution

It is the opposite, transcendental functions are only supported on the vector engine, not  on the scalar engine.

They operate at quarter rate, hence if you want to have a faster approximation you need to do it in less than 4 single precision operations.

Tzachi

View solution in original post

nou
Exemplar

Re: GCN SIMD vs SIMT

Jump to solution

I would benchmark it. Nothing is better than hard data.