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Cross Entropy Method

Last edited: August 8, 2025

This method introduces a search distribution instead of discrete points:

\begin{equation} p(\theta | \psi) \end{equation}

We want to know how parameters \(\theta\) are distributed, given some input parameters \(\psi\) (for instance, we assume parameters are gaussian distributed such as the mean/variance).

  1. Given this distribution, we sample \(m\) samples of \(\theta\) from the distribution. Those are our starting candidate points.
  2. We then check its policy for its utility via the Roll-out utility
  3. We want to take top \(k\) of our best performers, called “elite samples” \(m_{elite}\)
  4. Use the set of \(m_{elite}\) points, we fit a new distribution parameter \(\psi\) that describes those sample

This allows us to bound how many Roll-out utilities we are doing.

cross product

Last edited: August 8, 2025

constituents

additional information

lack of inverse of cross product

The cross product doesn’t have an inverse

geometric interpretation of cross product

\begin{equation} a \times b = |\vec{a}| |\vec{b}| \sin \theta n \end{equation}

where, \(n\) is the unit vector in some direction.

The length of the resulting vector in the cross product is the area of the parallelogram formed by the two vectors.

CrossFinder

Last edited: August 8, 2025

CrossFinder is a darkpool owned by Credit Suisse.

Features:

  1. Normal darkpooling
  2. Routing the transaction out to other exchanges and dark-pools if needed
  3. Measuring the latency of each other exchange, etc.

cryo-electron microscopy

Last edited: August 8, 2025

cyro-EM is a structure determination system of a solution (Dutta, M. 2018. J indian inst sci 98) to analyze a structural population of particles from TEM; the resulting 3-D structures obtained can be analyzed and classified.

“The Resolution Revolution”: much better structures to analyze because of high-fidelity cyro-EM

cyro-EM vs x-ray crystallography

cyro-EM can identify heterogeneous motions throughout the structure, instead of averaging out multiple structural combinations; instead of the “general” structure on average, we can get a collection of various states the particle can be in.

Crystals

Last edited: August 8, 2025