Year: 2020

Uncategorized

Talk: Gradient-based optimization for Deep Learning

This weekend I gave a talk at the Machine Learning Porto Alegre Meetup about optimization methods for Deep Learning. In this material you will find an overview of first-order methods, second-order methods and some approximations of second-order methods as well about the natural gradient descent and approximations to it. I took some long nights to prepare this material, so I hope you like it! You can download the PDF of the slides by clicking on the top-right menu.

– Christian S. Perone

Uncategorized

Visualizing sample simplex trajectories in Deep Learning

Softmax is a distribution over choices, it maps a vector into the probability simplex that is defined as \Delta_{n-1}=\{p\in\mathbb{R}^n\; \vert\; 1^\top p = 1 \; \; {\rm and} \;\; p \geq 0 \}, where the sum of all elements of the vector must equal 1. Softmax is used a lot in classification and I thought it would be interesting to visualize (when possible, on lower dimensions) the trajectories of individual samples in that simplex as predicted by the network while the network is being trained.

In the animations below you’ll see the trajectories of the sample individual sample (from the test set) over the simplex of 3 classes (dog, cat, horse) from CIFAR-10 and using a simple shallow CNN both with Adam and SGD. Each frame is generated after 10 optimization steps and the video is from 4 epochs with CIFAR-10 dataset with only the 3 aforementioned classes.

Trajectory of a CNN using Adam with LR of 0.001

Trajectory of a CNN using SGD with LR of 0.001 and momentum

Article, Philosophy

A new professional ethics: Karl Popper and Xenophanes’ epistemology

It is not a secret that I admire the work of Karl Popper, both as a philosopher but also as a very precise historian that tried to dismiss many misunderstandings of the past.

I was reading the book The World of Parmenides, which is a collection of Popper’s essays on the Presocratic Enlightenment, and found a very interesting insight on how the epistemology of Xenophanes led naturally to a professional ethics. This link isn’t widespread nowadays, but it certainly deserves more divulgation as it is a natural consequence of the conjectural knowledge we possess.

(more…)

Uncategorized

First early R0 estimate for Portugal COVID-19 outbreak

Just posting the first early estimate for the COVID-19 R_0 (basic reproduction number) in Portugal outbreak. Details on the image, more information to come soon. This estimate is taking into consideration the uncertainty for the generation interval and the growth.

Cite this article as: Christian S. Perone, "First early R0 estimate for Portugal COVID-19 outbreak," in Terra Incognita, 14/03/2020, https://blog.christianperone.com/2020/03/first-early-r0-estimate-for-portugal-covid-19-outbreak/.

Article

COVID-19 Analysis: Symptom onset to confirmation delay estimation for states in Brazil

Since the generation time of a virus is very difficult to estimate, most studies rely on the serial interval which is estimated from the interval between clinical onsets. Given that most analysis use the serial interval, it is paramount to have an estimate of the precise onset dates of the symptoms.

I did a analysis for all states in Brazil using data from SIVEP-Gripe, the complete analysis is available here.

In the image above, we can see the gamma mean estimate for the delay on each state in Brazil. Below you can see the distribution for Rio Grande do Sul / RS: