Correct alpha and gamma for image processing

This is a note on the correct usage of alpha blending, pre-multiplied alpha, gamma correction, and linear colors for image processing.

Accurate color conversions

This is a quick note for converting byte values colors in 0-255 back and forth to floating-point colors in 0-1 which avoids common errors.

Button debouncing and pattern matching

A robust, portable, extensible method for handling button presses when interfacing software and hardware.

A better quadratic formula algorithm

A robust algorithm for computing roots of quadratic equations, much better than common code.

Lomont floating point notes

Notes on floating point issues, including lists of facts and theorems useful for algorithm development.

Rtk Gps Project

I built a RTK-GPS gadget and wrote enough software to do basic GNS tasks such as finding distances, decoding GPS NMEA and RTCM messages, finding intersections, and doing boundary detection.

Computation: Theory, Methods, Limitations, and the Future

These slides are from a talk I gave on many aspects of computing, starting with classical computing (Hilbert’s 10th problem, Church and Turing, Godel, boolean functions, complexity theory, transistors, Moore’s law and demise), then going through physics (relativity, quantum mechanics, quantum field theory), and finally into quantum computing basics (qubits, superposition, entanglement, no cloning, basic gates) and quantum algorithms (Deutsch, Simon, Shor, Grover).

Then I cover advanced quantum topics, such as quantum machines,quantum complexity theory, the Quantum-Church-Turing-Deutsch principle, graph isomorphism, quantum error correction, and quantum security. A final speculative section covers even weirder computation ideas (closed timelike curves, string computing) and how computing seems intertwined with the nature of reality (It from Bit, Simulation Hypthesis, Free Will Theorem).

Intro to Wireless Communications

This talk is an intro to wireless communications, starting with the basic physics of EM waves and how they interact with materials, then how antennas work, then on to antenna properties and design. Next modulation schemes are discussed, showing how data is encoded and transmitted over noisy channels via modulation, spread spectrum, time and frequency division, and other methods. Noise in the form of doppler, intermodulation, and other causes is covered. Information theory (channel capacity, Shannon entropy, error correction) is covered. Finally specific protocols are analyzed under this framework: FM, NTSC, remotes, WiFi, Bluetooth, ZigBee, satellite radio, GPS, and cellular formats.

Cryptography Best Practices 2018

This talk covers cryptography best practices as of April, 2018. Background on each area is covered, with each section ending with a best practices slide. Sections are Symmetric Encryption, Asymmetric Encryption, Key Lengths, Hashing/HMAC, Password usage, Key Exchange, Random number generation, Digital Signatures,

Walking Ant Probability Problem

Here’s a math puzzle.

A Universal FRACTRAN Interpreter in FRACTRAN

Here’s FRACTRAN, a weird fraction based programming language, written in FRACTRAN.

Generating Uniform Random Numbers on [0,1]

How does one generate uniform random numbers in [0,1] using IEEE 754 floating point formats? It’s tricky.

Efficient divisibility testing

Here’s bit tricks for efficient divisibility testing.

Average segment length

What’s the average length of a segment chosen uniformly by area on a unit square?

How many prisoners?

This is a nicely hard problem in the common prisoners and warden format.

Pick a Number

Here’s a result that is completely non-intuitive.

Test site features

A post to test site features such as tables, math, code…