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Same instruction on all 8 EU?

Biren_Doshi
Beginner
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To get peak performance, all EU in single sub-slice should issue same instruction or in single EU only we need same instruction? At what granularity i should avoid branching ?

 

Thanks and regards,

Biren Doshi

 

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Jeffrey_M_Intel1
Employee
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The conditional mask is by EU thread.  Each thread can have 1-32 SIMD lanes.

This is lower granularity than by EU.  Each EU typically runs 7 threads.  The 2 FPUs per EU could in theory be saturated by only 2 threads but in practice running 7 means a higher chance of keeping them busy.

For more info, please see section 5.3.5 "SIMD Code Generation for SPMD Programming Models" in the Gen9 compute architecture documentation: https://software.intel.com/sites/default/files/managed/c5/9a/The-Compute-Architecture-of-Intel-Proce...

 

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