The conjugate gradient method is a commonly used approach to solve linear equations. In this blog I will describe the matrix generalization of this method and provide a toy implementation.

Frequently in a Quantum Chemistry code one needs to compute the trace of the produce of two symmetric matrices. This post describes a common method to do this without having to perform matrix multiplication.

Hotelling's method is a way to compute the inverse of a matrix. I will introduce the method, present a toy implementation, and describe situations where it might be applicable.