I am fairly new here, and this post may or may not be in the right section. I apologize if it's not where it's supposed to be.

In my work I need to solve a linear least square unconstrained problem. I found three LAPACK routines that can be useful :

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`SGELS(..)`

SGELSD(..)

SGELSY(..)

I compared them in terms of precision and execution time, and it allowed me to choose one, but now i am looking for a more in depth understanding.

Can any one explain me the differences between these methods?

Thanks

A.