Efficient techniques for the VaR decision problem ------------------------------------------------- Value at Risk (VaR) is a popular measure of the financial risk of a portfolio. Monte Carlo techniques are often used to estimate this quantity. One of the main draw backs of these techniques is the computational cost involved. Under certain conditions, the bottleneck is a matrix vector multiplication involved in the computation. In the VaR decision problem, we are interested not in the VaR itself, but in whether it exceeds a given threshold. In this talk, I will discuss linear algebra and computational geometry techniques that yield significant increases in speed for this problem. Some of these ideas have potential applications to information retrieval too.