## Ancenstral sampling

Didn’t know the name ancestral sampling before. It is just sampling p(x,y,z) as p(x) p(y|x) p(z|x,y). Or basically, it is just a special case of Gibbs sampling.

## Marching cube

A great explanation of the Marching Cube algorithm is here. The algorithm’s goal is to draw meshes of an implicit surface function \$latex f(x,y,z) = threshold\$. Based on the 8 corner points for each tiny cube is above or below the threshold, the mesh triangles for the cube can be easily determined. The algorithm then…

## Byzantine general problem

I thought I studied this before but can’t find a post from my blog. Byzantine generals problem was named by Leslie Lamport, the creator of LaTex. They consider a distributed consensus problem with the allegory that every general will need to agree on a broadcast message so that they can unify their attacks. It seems…

## Bandlimited channel

By Shannon-Nyquist theorem, a bandlimited signal can be completely reconstructed with \$latex 2W\$ samples per second. Think of the opposite way, this means that each second we have \$latex 2W\$ independent components that we can vary for each second. The total noise power per second is \$latex 2 W (N_0/2) = N_0 W\$ and as…

## One pager for proposal

A good slide from a workshop.

## Differential privacy

I need to work on a data privacy project and so am spending some time to review some notes I wrote couple years ago. I guess it would be a great exercise to reorganize them into a post series.  And this will be my first post of this series. 🙂 Introduction to data privacy From…

## Public key cryptography and RSA encryption algorithm

Let say if Alice would like to send a secret message to Bob, she may want to first encrypt the message before sending it. Modern cryptographic techniques all use some secret keys to encrypt and decrypt a message. For example, we may generate a random sequence with a predefined seed (the key) and take the…

## Goagent experience

I am in Shanghai a couple days and it is quite inconvenient with many websites blocked. I heard about “breaking” the wall but I didn’t realize it is quite fast and easy. All one needs is a software called goagent. It takes advantage of the google app engine. Here, I will assume that ones already…

## M/M/1 Simulation with Matlab

A simple simulation of M/M/1 queue with Matlab. The distribution of the number of “packets” in the system is computed and compared with the theoretical result. delta=0.1; % simulation step in sec lambda=0.1; % arrival rate in packets per second mu=0.2; % departure rate in packets per second rho=lambda/mu; M=50*3600/delta; % number of simulation step…

## Simulating Poisson process in Matlab

Below is a simple Matlab code to simulate a Poisson process. The interarrival times were computed and recorded in int_times. The times are then grouped into bins of 10 seconds in width and the counts are stored in count. lambda=1/60; % arrival rate per second (1 minute per packet) T=10*3600; % simulation time in second…