!!Con 2018 Notes

!!Con is a conference held every spring in New York City. It’s two days of lightning talks that can be about anything related to computers!

This conference is a great showcase of the diverse backgrounds of the NYC tech scene. I’m really going to miss it when I move back to the Bay Area.

Contents

• Day 1 Keynote
  • { }
• Session 1
  • Telling stories with traceroute!
  • Tales of ⌧! Can You Tell Your Story When Your Character Is Undefined?!
  • Turning Google Earth into SimCity 2000! (From Light to Pixels to Impossible Perspectives!)
  • We built a map to aggregate real-time flood data in under two days!
• Session 2
  • Moving towards dialogue: collaborating with your computer using typed holes!
  • Compressing the Library of Babel!
  • It’s super effective! Solving Pokémon Blue with a single, huge regular expression
  • Transform live video streams with code and a REPL!!
• Session 3
  • Creating an Arabic Programming Language!
  • Evil Twins and the Secret Lives of Linkers!
  • Satellites are talking to us! Let’s hear them out!
  • The joys of PICO-8 token crunching!! Or: what I learned about programming from being restricted on every side!
• Session 4
  • UX for Cats and Dogs!
  • If you could solve this word tile puzzle, you could solve the halting problem! (Too bad you can’t!)
  • So THAT’S how my phone knows where I am!
• Day 2 Keynote
  • Build skills through hobbies! Bring them to work!
• Session 5
  • Relativistic Software Calendars: It’s About Time!
  • Undo all the things!
  • Estimating the Value of Pi with a Dartboard and (Not so Much) Luck!
  • Ray-tracing and special relativity: Rendering objects near the speed of light!
• Session 6
  • Talking to my past self (without introducing temporal paradoxes!)
  • Four fake filesystems!
  • Using Postgres to \watch Star Wars!
  • If at first you don’t succeed at beating HQ Trivia, try cheating!!
• Session 7
  • The Man Comes Around: and so does his sound!
  • Step by Step: Algorithms that teach you math!
  • Whoa, pictures! A visual history of visual programming languages!
  • Fast, but not too fast! What 17th-century windmills can teach us about database migrations
• Session 8
  • The itty, bitty, tiny bytes that make up a Pokémon!
  • Pseudofractals! Accidental aesthetics where math meets pixels

Day 1 Keynote

{ }

Mimi Onuoha

• Exploring the implications of machine-readable world through art & programming
• “Embedded in every technology there is a powerful idea” —Neil Postman
  • Oral culture: prioritize memory.
  • Written culture: prioritize logical organization of thought.
  • Digital culture: prioritize data!
• Obsession with data as the object
  • Does it mean what you think it means?
  • Hard to tell when you don’t have context
• Pathways
  • Tracked location data of several groups for 2 weeks
  • Met in person to collect: make the collection relationship explicit, forcing people to think about it
• Unable to collect? Common reasons of missing data
  • Those with resources to collect don’t have an incentive to know
  • Resists “metrification”: things are hard to categorize or don’t inherently generate data
  • Nonexistence benefits or protects someone
• Art piece: cabinet of missing datasets
  • Filing cabinet with empty folders labeled with names of datasets that don’t exist
  • Flip through all the things we don’t know

Session 1

Telling stories with traceroute!

Karla Burnett

• How traceroute works
  • Packets have a time-to-live (TTL) to prevent getting stuck in routing loops
  • traceroute is a hack that sends packets with different TTLs to make different routers along the path respond
• Telling stories through traceroute
  • Send fake TTL expired messages from spoofed IPs
  • Reverse DNS maps IP to hostname, but the hostname doesn’t have to be real
  • Each line of the story needs a new IP: $3 per month

Tales of ⌧! Can You Tell Your Story When Your Character Is Undefined?!

Persa Zula

• Small boxes that show up in text when characters not defined
  • [ ]: “tofu,” so [X]: “not tofu”
• Displaying characters
  • Characters are encoded as codepoints in Unicode
  • Font’s cmap table maps codepoints to glyph identifier

Turning Google Earth into SimCity 2000! (From Light to Pixels to Impossible Perspectives!)

Logan Williams

• Perspective projection
  • Farther objects are smaller
• Orthographic projection
  • Satellite photo pointing sideways has no perspective: all lines are parallel
  • Used in drafting, art, and SimCity 2000
  • Only possible when image sensor is same size as object (flatbed scanner)
  • In rendering software, set field of view very small so input rays of light are almost parallel
• Doing this in real life?
  • Fly over the scene and take the same row of pixels from each frame
  • Ensures all pixels formed by light coming from the same direction
  • Produce images that represent time in addition to space

We built a map to aggregate real-time flood data in under two days!

Aruna Sankaranarayanan

• Chennai floods in 2015
  • Bad maps made it hard to communicate which roads were navigable
  • Google only lets you annotate locations, not streets
  • Used MapBox to crowdsource mapping during the floods
  • 600,000 people used the software, showing that simple tools can be really useful

Session 2

Moving towards dialogue: collaborating with your computer using typed holes!

Vaibhav Sagar

• Typed hole: something where you know the type but not the contents of the value
  • Can specify in Haskell using underscore _1, _2
  • Type inference tells you what the type should be
  • In Idris, a more powerful type system also includes list length, so type inference can even help you write snippets of code
• Untyped holes: don’t know what the type is, but still want help writing program
  • Open research topic

Compressing the Library of Babel!

David Turner

• Compressing the infinite library described in Borges’ short story
• gzip?
  • Works by finding identical sequences and inserting references back to them
  • On Babel: compression ratio is 1:1 because of pigeonhole principle
• Write a program?
  • Kolmogorov Complexity = size of compressed data + size of decompressor
  • Generation program only a few lines of Python
  • Suppose some pages are missing: pigeonhole principle means representing missing books requires storing entire book

It’s super effective! Solving Pokémon Blue with a single, huge regular expression

Alex Clemmer

• Pokémon Blue
  • Little boy leaves home to wander the world and catch Pokémon
  • Mostly wandering around in the grass (very tedious)
  • Create a regex which accepts iff the moves are a winning game
• How to solve?
  • Pokémon Blue is a finite state machine
  • Equivalence between FSM and regex (according to “nice book” by “this guy” Michael Sipser)
  • Simplify Pokémon to use ASCII world maps
  • World map → FSM → regex
• Differences from actual Pokémon game
  • Items can have state, player interaction
  • Players can hold items
  • Game has random encounters (use probabilistic regex)

Transform live video streams with code and a REPL!!

Mark Wunsch

• Live coding: code improv! Code as the user interface, applied to video streaming.
• Use Racket language and GStreamer multimedia framework
• Write in Racket REPL to manipulate video stream, draw stuff, PIP

Session 3

Creating an Arabic Programming Language!

Ahmed Abdalla

• Learning to program requires English proficiency
  • Not just keywords, but also error messages & documentation
  • English proficiency requires privileged backgrounds in some countries
• Noor: Imperative, Algol-style programming language for kids
  • Keywords are simple & informal so kids understand
  • Used his Sudanese dialect because languages reflect the aesthetics of their creators
• Arabic editor challenges
  • Bidirectional language is overall right-to-left, but English words within Arabic text are left-to-right
  • Ligatures required in the language, not just aesthetic

Evil Twins and the Secret Lives of Linkers!

Josh Bowman-Matthews

• Symbol defined twice in different .o files. What happens when you link?
  • If functions are not inline, linker complains about duplicate symbols
  • Inlining makes a copy of the function inside each .o file
  • Therefore, linker is allowed to pick one arbitrarily & not complain
• Don’t accidentally write the same function twice

Satellites are talking to us! Let’s hear them out!

Ed Medvedev

• “There are only a handful of things cooler than satellites”
• Radio amateur satellites: tiny satellites for ham radio
• Listening to satellites
  • You will need radio dongle for computer & antenna
  • Look up online when the ISS will be overhead
• ARISS: Amateur Radio on ISS
  • Runs BBS so you can chat with people relayed through space
  • Broadcast images & talk to astronauts sometimes

The joys of PICO-8 token crunching!! Or: what I learned about programming from being restricted on every side!

Ayla Myers

• PICO-8: game engine with retro graphics & sound, but modern programming
  • Artificial limits on bit depth, memory, code size (tokens), …
  • Built-in editors for everything
• Economics of the PICO-8 device
  • Trade-offs: smaller sprite sheet leads to more complex code
  • “Spent” code tokens to “buy” more sprites
  • Can draw PPF curve for tradeoff between e.g. code complexity & number of sprites

Session 4

UX for Cats and Dogs!

Joel Potischman

• Problem: daughter moved to college but misses cat
  • Manually send cat photos
  • Can the cat send us selfies?
• Solution
  • Train cats to come eat when the sound is played
  • Take a picture of cats while they wait for food
  • Feed the cats

If you could solve this word tile puzzle, you could solve the halting problem! (Too bad you can’t!)

Kamal Marhubi

• Tile puzzle (Post Correspondence Problem)
  • Tiles have symbols on top and bottom
  • Goal: order the tiles so that top and bottom say the same thing (can repeat tiles)
  • Not possible to tell whether a solution exists
• Reducing Turing machine to tile puzzle
  • Make a tile from each state somehow
  • ???
  • Solving the tile puzzle is the same as running the Turing machine
• Wikipedia has a really unclear explanation
  • “Some things are actually hard, and some things just have too many Greek letters”

So THAT’S how my phone knows where I am!

Mike Lazer-Walker

• Positioning throughout history
  • Latitude is easy because you can look at the sun
  • Longitude much harder, so people dead reckoned based on speed and time
  • Solved with accurate clock that allowed using time zone as a proxy for distance
• Urban canyon problem: GPS error gets really bad in cities
  • Skyscrapers bounce the signal, messing with the distance

Day 2 Keynote

Build skills through hobbies! Bring them to work!

Liz Fong-Jones

• Many years ago, a disowned trans woman who “almost didn’t make it”
• Growth comes from learning new skills
• Playing Puzzle Pirates game (2004–2008)
  • Some people made new players work without teaching the game
  • Learning mentorship: encouraging people to help newcomers by rewarding them
  • Organizing people: conquering an island requires multiple levels of coordinators to solve puzzles & distribute booty as reward
  • Active on community forums building diagnostic tools led to first tech job at Puzzle Pirates!
• World of Warcraft (2008–2012)
  • Building up new players’ skills to have a stronger team in next raid
  • Not all leaders are blameless after the team loses
• Eve Online (2012–present)
  • After fleet commander died, there was no communication & everyone else died
  • In incident response, “any call is better than no call”
  • Value your trustworthiness: not scamming in the game pays off when other players trust with other opportunities
• Factorio (2017–present)
  • Learning what’s the most important to automate right now
  • Refactoring a complex, running system
• Playing these games taught her management skills in a safe environment before she became a manager for real
  • Don’t be afraid to list non-traditional background on your resume
• Intentional skill building
  • What skills will your next project require?
  • Does this activity help me get closer? (Or just mindless play?)

Session 5

Relativistic Software Calendars: It’s About Time!

John Feminella

• Software makes assumptions
  • About the machine (“integers are 32 bits”)
  • About the world (“everyone has a real name”)
• Time is one of these assumptions
• What is time?
  • Originally measured by motion of earth & moon
  • Calendar is an abstract representation of this motion
  • Software calendars bake in assumptions about being on earth
• Enter relativity
  • Time distorts depending on the velocity of observer
  • GPS is one of the few programs that accounts for relativity

Undo all the things!

Tom Ballinger

• bpython is a Python interpreter that can undo the effects of expressions
  • Works by saving commands & rerunning only some of them
  • Could be slow
  • Doesn’t work if there are side effects
    • Random numbers, time, reading files
    • Non-idempotent actions: saving to files, buying shoes online
• Use fork() to save state
  • Fork every time you run a command
  • Undo goes back to previous process
  • Build this into readline() & run with LD_PRELOAD
    • Works with unmodified interpreters!
    • readline() now forks your program lol
• Building an undo-able Lisp interpreter from scratch
  • Save periodic snapshots
  • When code changes, roll back to the snapshot before that code was run
  • JavaScript version because “the word has to be on the left side of the parentheses or the programming language will never be popular”

Estimating the Value of Pi with a Dartboard and (Not so Much) Luck!

Stephen Tu

• Estimating pi
  • Sample a square uniformly at random
  • Percentage inside circle is \( \pi / 2 \)
• Estimating with error
  • Define an epsilon \( \epsilon \) which is the error on our estimate
  • Define a probability (95%) that the estimate is within \( \epsilon \)
  • Need 100x more samples for 10x reduction in \( \epsilon \)

Ray-tracing and special relativity: Rendering objects near the speed of light!

Lucy Zhang

• If an object is moving near the speed of light, what would a photo look like?
• Computer graphics
  • Ray casting: for each pixel, figure out where the light ray from the camera hits in the scene
• Relativity
  • Light can never exceed speed of light, even if the light is on a fast-moving train
  • Lorentz transformation converts between two coordinate systems that are moving relative to each other
• Relativistic raytracing
  • Define the rays toward the object with a 4th parameter, time
  • Use Lorentz transformation
  • Do intersection normally
  • As cube moves faster, it compresses more (expected) & appears to rotate (why?)
• Terrell rotation
  • Rotates because farther light takes longer to reach the camera
    • Like rolling shutter effect but for relativity!
  • Anyone with a computer can “rediscover” Terrell rotation with a bit of code!

Session 6

Talking to my past self (without introducing temporal paradoxes!)

Andrew Louis

• Stores all data about himself
  • “MSN was this cool software package that taught high schoolers how to type really fast”
• Training a bot on chat logs
  • Train RNN to reproduce chat logs from high school
  • Sequence-to-sequence to respond to other messages
    • Originally developed for machine translation
  • Bot tends to converge on safe responses like “lol” and “ya” which work in any situation
  • Tends to respond with nonsense
• Why is it hard?
  • Training data won’t capture general knowledge about the world
  • Needs working memory, not just the previous message
  • “Before submitting a conference talk, make sure you’re not committing to solving an open research problem”

Four fake filesystems!

Omar Rizwan

• Files are anything that you can open, read, write, close using a path
• GrabFS
  • Contains screenshots of each process’s windows
  • Use shell script with cp to take screenshot every second
• btfs (BitTorrent filesystem)
  • Downloads blocks as requested
  • Opening part of a file doesn’t require downloading whole thing
• ytfs (YouTube filesystem)
  • Making directory is a search query
  • Directory populated with movie files of search results
• Git filesystem
  • Exposes remote repository as a directory
• Get to reuse existing tools & UI
  • Plan 9 operating system takes filesystem idea to the extreme

Using Postgres to \watch Star Wars!

Will Leinweber

• Using psql, the command-line Postgres program, to watch ASCII Star Wars
  • Import frames as database rows
  • Store a function in the database that prints each row

If at first you don’t succeed at beating HQ Trivia, try cheating!!

Hung Truong

• HQ Trivia is fun but we want to win
• Pipeline
  • iOS Vision framework to detect text
  • Tessaract library for OCR
  • Google the question with all answers
  • Pick the answer with the most occurrences

Session 7

The Man Comes Around: and so does his sound!

Vince Allen

• Johnny Cash did gospel music at the beginning & end of his career
  • What are the differences between the two periods?
• Identifying gospel songs
  • Topic modeling: assigns words to categories to classify the entire text
  • Apply topic modeling to lyrics
  • Pick the category with religious terms
• Comparing songs acoustically
  • Take a spectrogram of the song
  • Convert this to a vector
  • I didn’t really understand the rest :-(

Step by Step: Algorithms that teach you math!

Evy Kassirer

• Building a step-by-step solver for teaching math
• Computer algebra systems
  • SymPy can simplify expressions symbolically, which sounds like a solver
  • Goal is to get the answer, so they represent division \( a / b \) as \( a \times b^{-1} \)
  • This would be confusing for explaining stuff
• Building their own solver
  • Search the parse tree for patterns like “number + number”
  • Apply rules to transform to equivalent tree
  • Identified which rules were applied to find relevant lecture videos

Whoa, pictures! A visual history of visual programming languages!

Emily Nakashima

• Visual Programming Languages (VPLs)
  • Programming & documentation are all in words
  • Our brains are really good at visual stuff
• Examples
  • Scratch: Build programs with blocks
  • GRAIL (1968): Draw flowcharts which are converted to programs with OCR
  • Pygmalion (1975): Visually show state on screen
  • Cube (1995): 3D flowcharts?
• Challenges
  • Diffing & merging visual programs
  • Humans can handle more unique words (symbol names) than unique shapes
  • Hard to represent complexity without losing the simplicity of visual programming
  • Unclear whether VPLs actually make you program differently
    • People prefer whatever they learned first
• Good applications of VPLs
  • Simple systems: Twilio phone tree designer
  • Kids & learning

Fast, but not too fast! What 17th-century windmills can teach us about database migrations

Wander Hillen

• Windmill design
  • Whole windmill rotates to match wind direction
  • When windmill moves too quickly, slats automatically open to catch less wind
  • Big changes in load: wind energy increases with \( \vert v \vert^2 \)
• WeTransfer depends on automation to handle load changes
  • Throttle expensive background tasks when the system is busy

Session 8

The itty, bitty, tiny bytes that make up a Pokémon!

Jan Mitsuko Cash

• Pokémon data structure
  • 232 bytes each
  • Stores properties like species ID, experience, nickname
  • Backward compatible between generations 1–2, and gen 3 on
  • Gen 3 added encryption

Pseudofractals! Accidental aesthetics where math meets pixels

Jes Wolfe!

• Generate topographical map
  • For each pixel, compute color as \( (x^2 + y^2) \bmod 2 \)
  • Weird artifacts! Doesn’t look like a parabolic topo map at all
• Aliasing
  • Caused by Nyquist limit
  • If you zoom out too far, frequency of pixels (sampling) is no longer high enough to show frequency of topo map lines
• Making art
  • Zoom out slowly to watch the aliasing pattern change
  • Use \( (x^2 + y^2) \bmod N \) and assign to colormap of N colors