I have windows form app using C#. I need to do incremental search inside the grid control from a text box. The problem when I type few letters the app hangup for 6 seconds until it display what I wrote and filter the grid. Currently there are 3 million records. Is there a way to make incremental search faster ?

I am receiving a point cloud from a 3d scanner system which has already had outliers filtered. It is roughly cylindrical and an example looks like this:
Front view
Isometric view

I need to optimize the following function with low level optimizations (No SIMD, Multi threading). I already applied a lot of optimizations and got it ~65% faster but it is possible to get it 200% faster. I am practicing on code optimization, some explaination would be welcome.

I found the nested if run faster than serialized if and it confused me.