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.
Ancenstral sampling
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Category: Study notes
Marching cube
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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
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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
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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
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A good slide from a workshop.
Differential privacy
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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
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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
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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
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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
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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…