About Logical core and execute instruction

[ALife]

Hello,

Could you explain about it?

Why?

This is important to realize when you examine your computer hardware and estimate performance gains of a parallel application.

For our examples of performance estimations using Amdahl's and Gustafson's laws, we will only be counting physical cores because technically logical cores, in a single physical core, cannot execute instructions during the same clock cycle.

[AP16]

technically logical cores, in a single physical core, cannot execute instructions during the same clock cycle.

Not 100% true, logical cores contains a lot of execution units: ALUs, FPUs, VEs, and scheduler can dispatch several instructions on-fly between 'lines' (consists of several EUs) if there are no resource conflicts, i.e. if all the data fits into L1 cache (possibly, L2 too). Skylake core can execute up to 5 instructions on different stages simultaneously.