How to display math operators not in italic?

Question

I'm trying to write the following equation:

\rho = \max \left\{ \frac{|\mathbf{w} \cdot \mathbf{x^{(i)}} + b|}{\|\mathbf{w}\|} \right\}

but the PDF output renders the math operator \max in italic instead of upright. I've tried the same with \log and \cos, and they behave just the same. What am I doing wrong here?

Document class: memoir

Packages: pgf, fontspec, graphicx, microtype, unicode-math, amsmath

The following code reproduces the problem in different systems:

\documentclass{memoir}
\usepackage{unicode-math}
\usepackage{amsmath}
\begin{document}
Yay, a dual problem:
\begin{equation}
\max_{\mathbf{\alpha}} \left\{ \sum_{i=1}^m \alpha{(i)} \right\}
\end{equation}
\end{document}

Answer 1

The solution: Load the amsmath package before the unicode-math package. (I think this is mentioned in the user guide of the unicode-math package...)