NYAI #7 - Top-down vs. Bottom-up Computational Creativity by Dr. Cole D. Ingraham

NYAI #7 (SPEAKER SERIES): Data Science to Operationalize

Machine Learning (Matthew Russell) & Computational Creativity

(Dr. Cole D. Ingraham DMA)

Top-down vs. Bottom-upComputational Creativity

Dr. Cole D. IngrahamNYAI Nov. 22, 2016

About Me

• originally from Santa Clara, CA

• DMA Music Composition

• currently working as lead developer at Amper Music (www.ampermusic.com)

• www.coleingraham.com

Abstract

• what does computational creativity mean, and what are some approaches?

• what are some examples of these approaches?

• how to know the best way a particular problem could be solved?

• primarily concerned with choosing an appropriate approach, less about implementation

Defining Creativity

• Creativity: the use of the imagination or original ideas, especially in the production of an artistic work.

• Artistic: having or revealing natural creative skill; aesthetically pleasing

• Aesthetic: a set of principles underlying and guiding the work of a particular artist or artistic movement

• very circular, difficult to concretely define

Defining Creativity

• my personal requirements:

• originality/novelty

• having some unified set of guiding principals

Top-Down Approach

• finding an answer that:

• is novel and useful (either for the individual or for society)

• demands that we reject ideas we had previously accepted

• results from intense motivation and persistence

• comes from clarifying a problem that was originally vague

https://en.wikipedia.org/wiki/Computational_creativity#Defining_creativity_in_computational_terms

Bottom-Up Approach

• artificial neural networks

• machine learning

• data, data, and more data

https://en.wikipedia.org/wiki/Computational_creativity#Defining_creativity_in_computational_terms

Comparing Approaches• Top-Down

• primarily code driven

• dependent on defining structure

• requires considerable development time to be effective

• very “hands on” (things only improve as the code base improves)

• Bottom-Up

• primarily data driven

• heavy use of statistical analysis

• requires considerable amounts of data to be effective

• very “hands off” (run the algorithm on the data and wait)

• 5

Comparing Approaches• Top-Down

• you define the structure of your program

• Bottom-Up

• you learn the structure of your program from analyzing data

Generation Vs. Analysis• Generation

• create something that does not exist

• novel output

• example use: music composition

• Analysis

• extract information from something that exists

• generalization of the input

• example use: music suggestion (Spotify, Pandora, etc.)

Generation & Analysis

• the creation of something new can/should be informed by analysis of previous work

• in order to analyze previous work, the work must already exist

• ... chicken and egg

Generation by Analysis

• analysis produces generalizations/averages of all input

• this can lead to largely homogenous output

Generation, Then Analysis

• with some target in mind, generate output, then analyze it and see how close you got

• heuristic “guess and check” with no generation-time feedback

Generation, No Analysis

• create output without analyzing anything before or after

• you must know what you are going to get

• ... or you must not care what you are going to get

How to know what approach use?

It depends!

Generation / Analysis

• examples:

• compile-time code optimization: generate, analyze, repeat n times

• absolute realism: analyze, then generate (conceptually)

• generative abstract art: generate, do not analyze (sometimes)

Novelty

• introducing variance into the programs output

• important considerations:

• how much variance?

• how to determine what can be varied?

• how much/little control over the variance you want/need?

How Much Variance?

• largely subjective and project dependent

• beware of probability-driven decisions:

• probabilities say how frequently something happens

• probabilities do not inherently say why something should happen

What Can Be Varied?

• largely subjective and project dependent

• example - text generation:

• synonyms can vary a sentence without fundamentally changing its meaning

• sentence structure and grammar are far less flexible

How to Control Variance?

• largely subjective and project dependent (sensing a theme?)

• some options:

• explicitly defined seeding and propagation of pseudo-randomness

• working with finite quantities of input parameters

A Note on Randomness

• nondeterministic code is a nightmare to QA

• interaction between many deterministic operations can create seemingly random outcome

• (my opinion) it’s a better use of time to work on deterministically defined variance than it is to weed out undesired results from nondeterministic code

In the News

Google

• neural network based approach (TensorFlow)

• uses a large training set

• limited by availability of data (not a problem for Google)

Wavenet(Google DeepMind)

• input: raw audio

• output: raw audio

• aimed at improving speech synthesis (very good at this)

• also used for music generation (less good at this)

Wavenet“Since WaveNets can be used to model any audio signal, we thought it would also be fun to try to generate music. Unlike the TTS experiments, we didn’t condition the networks on an input sequence telling it what to play (such as a musical score); instead, we simply let it generate whatever it wanted to. When we trained it on a dataset of classical piano music, it produced fascinating samples [...]”

https://deepmind.com/blog/wavenet-generative-model-raw-audio/

Wavenet• “trained it on a dataset of classical piano music”

• single instrument, single genre

• “we didn’t condition the networks on an input sequence telling it what to play (such as a musical score)”• no large scale structural awareness

• “let it generate whatever it wanted to”• no external input

...what about top-down news?

Top-Down News?

• none that I’m aware of

• not a buzzword like neural networks

• (my opinion): everyone uses a top-down approach to some degree, they just don’t feel the need to talk about it

Why am I talking about it then?• to emphasize that:

• AI is more than just data science

• defining the structure of your problem is integral to finding its solution

• there are many more valid approaches to creative AI than what gets all the attention

• one should use the right tool for the right job

• some balance between top-down and bottom-up is often the right choice

Project Example: Amper Music• Goal: create an AI music composition platform that lets users create

personalized, professional quality music instantly with no experience required.

• Requirements:

• speed: it must be fast!

• quality: it must be believable!

• control: it must be collaborative!

Requirement: Speed

• neural networks are s l o w

• hand tuned algorithms can be fast

• lookup operations are very fast

Requirement: Quality

• neural networks can be very accurate, given a training set of sufficient size and quality

• most musical training (theory, performance practice) can be defined in code

• we:

• don’t (currently) have access to an appropriate training set

• do have a team of developers who are also highly trained professional musicians

Requirement: Control• neural networks are “black boxes that just do what they do”

• defining music as a hierarchical structure offers handles to various aspects directly

• multiple levels of control:

• intuitive enough for the non-musician to use effectively

• powerful enough for the professional musician to use without feeling limited

Our Solution• define various levels of musical structure in a declarative manner

• use machine learning / neural networks to generate data for all defined structural levels offline, as data becomes available, that can be used to augment runtime decisions

• structure the program in a way that can be easily scaled with machine learning, but works without it

• keep the “black box” parts of the program as minimal and confined as possible

Tooling

• runtime: Haskell

• offline: Haskell, Python, anything else (it’s offline!)

Tooling• Why Haskell?

• compiled (fast)

• functional language (great for music and AI, like LISP)

• statically typed (safe, easy to maintain and refactor)

• Why Python?

• availability of libraries (TensorFlow as one example)

• scripting layer on top of C(++) (easier to use, still fast)

• used extensively in data science

Tooling• Why Haskell?

• compiled to machine code (fast)

• functional language

• statically typed (safe, easy to maintain and refactor)

• Why not Python (for runtime)?

• interpreted / compiled to bytecode

• not a functional language (I wanted to use a functional language)

• dynamically typed (can be a nightmare to maintain, compared static typing)

Thank you

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