how to write programs that are right
play

How to write programs that are right - lessons from science for - PDF document

Aug 23, 2023 •192 likes •658 views

How to write programs that are right - lessons from science for software engineering Greg Detre @gregdetre 28th September, 2013 BarCamp Tampa @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 1 @gregdetre, blog.gregdetre.co.uk

  1. How to write programs that are right - lessons from science for software engineering Greg Detre @gregdetre 28th September, 2013 BarCamp Tampa @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 1

  2. @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 2 if you want to chat through some of these ideas, I’m new to Tampa and looking to be part of the community, so drop me a line

  3. WHO IS THIS FOR? @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 3

  4. better to fail than be invisibly wrong @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 4 this is about writing programs where you really care that the answer is right. for example, if you’re analysing data, and you’re going to make a big decision or publicise the results, you really care that the analysis is right, or at least, that you understand it and it’s doing what you think it’s doing you’d rather it crashes than give you the wrong answer this is not about scalability either you know what you want it to do

  5. @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 5 you don’t mind if it takes longer. though if 90% of your time is debugging, slowly & surely may even be faster in the long run

  6. ME ME ME @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 6

  7. e r t e D g e r G r D @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 7 I'm Greg Detre I have a PhD in the neuroscience of human memory and forgetting from Princeton

  8. @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 8 i spent my days scanning people’s brains including my own it turned out to be smaller than I’d hoped

  9. @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 9

  10. @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 10

  11. How to write programs that are right - lessons from science for software engineering @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 11 by the way, if you have a question, just make a noise like a wounded wildebeest and we can talk about them together

  12. TOOLS @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 12

  13. Version control Git @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 13 If you program but don’t use version control, you’re like a Michelin chef trying to cook over a bonfire you absolutely should be

  14. WRITE FOR A STRANGER @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 14

  15. Imagine the person reading your code is hungry, tired, has a violent history, and knows where you live. @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 15 The person reading my code is usually ME (in which case, all 4 are true) In a year’s time, you will be a stranger to your present self.

  16. Good comments High-level goal: what is it trying to achieve? What kinds of inputs does it expect? Examples What kinds of outputs does it return? Examples I tried another way, but ended up doing it this way because... Explain unusual/complex bits Comment before you write the code @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 16 Examples of bad comments: Bad comments % I'm so sorry about this next bit of code. ... % Loop over 100 times For x:1:100

  17. Good coding practices Break functions into bite-sized chunks each one a separate concept encapsulation Don’t repeat yourself Variable naming Etc http://www.python.org/dev/peps/pep-0020/ https://github.com/thomasdavis/best-practices#programming-best-practices-tidbits @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 17

  18. TESTING @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 18

  19. Unit tests If I call this function with input X, I expect to get output Y back Helps you structure your code And the tests serve as a kind of how-to guide You’re probably doing this anyway as you go @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 19 structuring if it's easy to test, it'll be easy to understand and refactor probably doing this anyway as you go tests just reify that

  20. Guard against new bugs in old code Run your unit tests every time you run your analysis @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 20 Otherwise you might break something that used to work, and not realize it

  21. Defensive coding asserts and sanity checks fail immediately if things are wrong @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 21 sanity checks e.g. confirm the dimensions, range of values, type of values fail immediately that way you'll notice early on in time and near to the cause of the problem rather than 2 weeks later and in a downstream part of the analysis

  22. Eyeball it examples of what this might help you see? @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 22 Run imagemat at large scale. You'll easily spot - outliers - stripes, e.g. if the scanner wasn't collecting for a while one row is all-zeros baseline di fg erences before/after gradients/drift over time

  23. HOSTILE WITNESS @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 23 [cf the Cartesian demon] i.e. your program/data are out to get you. ask leading questions and challenge it If the examining attorney who called the witness finds that their testimony is antagonistic or contrary to the legal position of their client, the attorney may request that the judge declare the witness hostile If the request is granted, the attorney may proceed to ask the witness leading questions. Leading questions either suggest the answer ("You saw my client sign the contract, correct?") or challenge (impeach) the witness' testimony.

  24. (e.g. MovieLens/Netflix-style dataset) movies About a boy Babel Caddyshack ... anna 4 3 users bill 2 5 charlie 1 2 1 ... @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 24

  25. 3 teams 1. Analysis writers 2. White-box testers 3. Hostile witnesses @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 25 your data is a hostile witness get a friend to be the hostile witness. ask them to try and create data that would trick the analysis

  26. Write the analysis @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 26 Most popular movies? Which movies are most similar to one another? Which are the hardest movies to predict? What subsets of movies tend to get rated together? Genres? Recommendations Who's the most accurate rater? Are some raters fake/spammers?

  27. Write the analysis Most popular movies? Which movies are most similar to one another? Which are the hardest movies to predict? What subsets of movies tend to get rated together? Genres? Recommendations Who's the most accurate rater? Are some raters fake/spammers? @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 26 Most popular movies? Which movies are most similar to one another? Which are the hardest movies to predict? What subsets of movies tend to get rated together? Genres? Recommendations Who's the most accurate rater? Are some raters fake/spammers?

  28. Creating hostile datasets @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 27 try baseline increasing one movie by a big margin try zeroing out an entire genre try making all the movies belong to the same genre try something subtle that won't be obvious visually, e.g. add a little randomness to each of the values (they're supposed to be ints/bools) steganography

  29. Creating hostile datasets try baseline increasing one movie by a big margin try zeroing out an entire genre try making all the movies belong to the same genre try something subtle that won't be obvious visually, e.g. add a little randomness to each of the values (they're supposed to be ints/bools) steganography @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 27 try baseline increasing one movie by a big margin try zeroing out an entire genre try making all the movies belong to the same genre try something subtle that won't be obvious visually, e.g. add a little randomness to each of the values (they're supposed to be ints/bools) steganography

  30. LOTS OF BABY STEPS @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 28

  31. How do you eat an elephant? Validate on small data, iterate quickly, scale up • Define your metric • Run it on small data - subsample (carefully) • Show that you get better as you add more data @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 29 how do you eat an elephant? one bite at a time. start small, with a tiny subset of your data. that way, the algorithm runs quickly while you're prototyping

  32. CANARIES IN THE DATACOALMINE @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 30

  33. Fake data Generate data that looks exactly the way you expect Can be hard to do, but often helps you think things through Confirm that the output looks as it should Useful for orienting audience in presentations @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 31

  34. Set expectations with fake data @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 32

  35. ? real data @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 33

  36. it’s supposed to look like this synthetic data @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 34

  37. ... now it makes sense synthetic real @gregdetre, blog.gregdetre.co.uk Friday, 1 November 2013 35

Recommend

Motivations Chapter 13 Abstract Classes and You have learned how to write simple programs

Motivations Chapter 13 Abstract Classes and You have learned how to write simple programs

Motivations Chapter 13 Abstract Classes and You have learned how to write simple programs Interfaces to create and display GUI components. Can you write the code to respond to user actions, such as clicking a button to perform an action?

344 views • 10 slides
Programs, and Java 1 Objectives To Know the basics To write a simple Java program To

Programs, and Java 1 Objectives To Know the basics To write a simple Java program To

Chapter 1 Introduction to Computers, Programs, and Java 1 Objectives To Know the basics To write a simple Java program To know error types To Know basic syntax of a Java program 2 Programs Computer programs , known as software

473 views • 36 slides
CSC 143 Introduction Classes have proven very useful They help us write programs the way

CSC 143 Introduction Classes have proven very useful They help us write programs the way

CSC 143 Introduction Classes have proven very useful They help us write programs the way we Inheritance view the world: interface vs implementation There is more to come! Java supports object oriented programming, i.e.,

255 views • 7 slides
Motivations You have learned how to write simple programs to create and display GUI components.

Motivations You have learned how to write simple programs to create and display GUI components.

9/19/2017 Chapter 13 Abstract Classes and Interfaces Liang, Introduction to Java Programming, Tenth Edition, (c) 2015 Pearson Education, Inc. All 1 1 rights reserved. Motivations You have learned how to write simple programs to create and

739 views • 16 slides
Models In Parallel Computation It is difficult to write programs without a good idea of how the

Models In Parallel Computation It is difficult to write programs without a good idea of how the

Models In Parallel Computation It is difficult to write programs without a good idea of how the target computer will execute the code. The most important information is knowing how expensive the operations are in terms of time, space, and

660 views • 42 slides
Getting CS undergraduates to write N. Abu-Ghazaleh, I. Cervesato Y. Cooper, A. Karatsolis, K.

Getting CS undergraduates to write N. Abu-Ghazaleh, I. Cervesato Y. Cooper, A. Karatsolis, K.

Getting CS undergraduates to write N. Abu-Ghazaleh, I. Cervesato Y. Cooper, A. Karatsolis, K. Harras K. Oflazer, T. Sans Contexts Computer Science ber-nerd culture: we write programs, not English That's how we were taught!! Real world

440 views • 17 slides
CPSC 213 for Java and C programs you will trace, write, read load code into Eclipse

CPSC 213 for Java and C programs you will trace, write, read load code into Eclipse

The Big Picture Languages and Tools Lab/Assignment 1 Build machine model of execution SM213 Assembly SimpleMachine simulator CPSC 213 for Java and C programs you will trace, write, read load code into Eclipse and get it

9.69k views • 3 slides
Elementary Programming 1 Objectives To write Java programs to perform simple calculations

Elementary Programming 1 Objectives To write Java programs to perform simple calculations

Chapter 2 Elementary Programming 1 Objectives To write Java programs to perform simple calculations To obtain input from the console using the Scanner class To use identifiers to name variables, constants, methods, and classes To

947 views • 56 slides
Methodology, and Tools to Write Bug-Free Programs Presented by Paolo Antonucci 04/05/13 About

Methodology, and Tools to Write Bug-Free Programs Presented by Paolo Antonucci 04/05/13 About

K. Rustan M. Leino, Peter Mller Using the Spec# Language, Methodology, and Tools to Write Bug-Free Programs Presented by Paolo Antonucci 04/05/13 About this paper This paper is more similar to a practical tutorial than a research paper.

628 views • 19 slides
Last time Introduced type inference can write type-safe programs without writing CS 611

Last time Introduced type inference can write type-safe programs without writing CS 611

Last time Introduced type inference can write type-safe programs without writing CS 611 down types explicitly Advanced Programming Languages useful for higher-order functions because types are large, obscure code Andrew Myers

393 views • 3 slides
4 5 6 CSE 142 vs CSE 143 CSE 142 / AP CS A CSE 143 You learned how to write Return of

4 5 6 CSE 142 vs CSE 143 CSE 142 / AP CS A CSE 143 You learned how to write Return of

4 5 6 CSE 142 vs CSE 143 CSE 142 / AP CS A CSE 143 You learned how to write Return of the objects programs and You learned to solve decompose large more complex tasks problems with: efficiently Print statements Data

705 views • 22 slides
Advanced Placement Java Chapter 10 Introduction to Arrays Objectives Write programs

Advanced Placement Java Chapter 10 Introduction to Arrays Objectives Write programs

Advanced Placement Java Chapter 10 Introduction to Arrays Objectives Write programs that handle collections of similar items. Declare array variables and instantiate array objects. Manipulate arrays with loops, including the

710 views • 37 slides
Introduction to Programming Systems CS 217 Fall 2001 1 Goals Master the art of

Introduction to Programming Systems CS 217 Fall 2001 1 Goals Master the art of

Introduction to Programming Systems CS 217 Fall 2001 1 Goals Master the art of programming exploit abstraction, modularity, interfaces write efficient programs write robust programs Learn C and the

714 views • 6 slides
CSCI26I File I/O in Detail ? Review Programs can read and write files to disk And from

CSCI26I File I/O in Detail ? Review Programs can read and write files to disk And from

CSCI26I File I/O in Detail ? Review Programs can read and write files to disk And from any stream ! #include <fstream> ifstream my_file_object(filename.ext) Use while loops to repeatedly read from the stream

781 views • 14 slides
Gyan-key read + write + speak Till date 41 programs and contests were successfully conducted for

Gyan-key read + write + speak Till date 41 programs and contests were successfully conducted for

Gyan-key read + write + speak Till date 41 programs and contests were successfully conducted for G y an- k ey school students, teachers & Principals, which saw participation of 2,38,000 rural students (You can see this communication in our

642 views • 48 slides
Gyan-key read + write + speak Till date 41 programs and contests were successfully conducted for

Gyan-key read + write + speak Till date 41 programs and contests were successfully conducted for

Gyan-key read + write + speak Till date 41 programs and contests were successfully conducted for G y an- k ey school students, teachers & Principals, which saw participation of 2,38,000+ rural students (You can see this communicationin our

874 views • 52 slides
How to write and prove programs with constraints and linear logic? Thierry Martinez Contraintes

How to write and prove programs with constraints and linear logic? Thierry Martinez Contraintes

How to write and prove programs with constraints and linear logic? Thierry Martinez Contraintes Project-Team INRIA Junior Seminar, 18 October 2011 Contraintes project-team Topic Formal semantics for programming languages Methods Logic

898 views • 55 slides
Using Graphics Building Java Programs Supplement 3G Introduction So far, you have learned how

Using Graphics Building Java Programs Supplement 3G Introduction So far, you have learned how

Using Graphics Building Java Programs Supplement 3G Introduction So far, you have learned how to: output to the console break classes/programs into static methods store and use data with variables write for loops for repetitive

407 views • 30 slides
Chapter 1 Introduction to Computers, Programs, and Java 1 Objectives To Know the basics

Chapter 1 Introduction to Computers, Programs, and Java 1 Objectives To Know the basics

Chapter 1 Introduction to Computers, Programs, and Java 1 Objectives To Know the basics To write a simple Java program To know error types To Know basic syntax of a Java program 2 Programs Computer programs , known as software

370 views • 36 slides
Scaling Program Synthesis by Exploiting Existing Code James Bornholt Emina Torlak University of

Scaling Program Synthesis by Exploiting Existing Code James Bornholt Emina Torlak University of

Scaling Program Synthesis by Exploiting Existing Code James Bornholt Emina Torlak University of Washington Synthesis: write programs automatically Syntax Semantics Synthesis: write programs automatically Syntax Semantics Synthesis: write

1.02k views • 87 slides
Read Write Inc. Phonics MISS CASBAN About Read Write Inc Phonics

Read Write Inc. Phonics MISS CASBAN About Read Write Inc Phonics

Read Write Inc. Phonics MISS CASBAN About Read Write Inc Phonics http://www.ruthmiskin.com/en/resources/parent-tutorial-1-understanding- read-write-inc-phonics/ The core purpose of Read Write Inc is to teach every child to read and to

478 views • 18 slides
How to Write Code Section 1.31.4 Dr. Mayfield and Dr. Lam Department of Computer Science

How to Write Code Section 1.31.4 Dr. Mayfield and Dr. Lam Department of Computer Science

How to Write Code Section 1.31.4 Dr. Mayfield and Dr. Lam Department of Computer Science James Madison University Sep 11, 2015 CS 280 weekly rubric Submit programs via Canvas for partial credit Trying two problems is a C Solving

276 views • 12 slides
Do Now! 1. On card write grade level you teach (Elementary or Secondary) 2. Write names of 3

Do Now! 1. On card write grade level you teach (Elementary or Secondary) 2. Write names of 3

Do Now! 1. On card write grade level you teach (Elementary or Secondary) 2. Write names of 3 artists/art works you regularly use for studio production lessons. 3. During presentation, when prompted, write an open-ended question that could

618 views • 40 slides
Programming in the small, medium, large You must be able to write itoa to be able to write

Programming in the small, medium, large You must be able to write itoa to be able to write

Programming in the small, medium, large You must be able to write itoa to be able to write hyperwag You must understand the difference between a pointer and a reference to write hyperwag You must know about templates, copy constructors,

531 views • 6 slides

More recommend