tfl: mul_test: optimize the MultiDimBroadcastSubshard tests
You describe a 0.6% improvement on the performance of a test. I am not approving this. > You describe a 0.6% improvement on the performance of a test. I am not approving this.

I didn't run too much iterations, just tried more and the improvement can be 3% to 4% on my end now.

Hi @qukhan in case of it is a correct change, why don't you want to take it? Improvemence accumulates step by step, no?
Optimize to avoid doing duplicate calculation to speed up the cases *MultiDimBroadcastSubshard*.

This improves the execution time for example from 1m11.090s to 1m10.645s.