Harmful GOTOs, Premature Optimizations, and Programming Myths are the Root of all Evil

See: http://videlalvaro.github.io/2015/02/programming-myths.html

This talk is a discussion of the paper Structured Programming with Go To Statements by Donald Knuth, in which some programming myths that populate our industry are reviewed.

Maxims like "Go To Considered Harmful" or "Premature optimization is the root of all evil" are revisited and analyzed in context, both in the paper in which they appeared, and by further comments made by the authors, which are usually ignored.

At the same time a glimpse is given about what was the computer industry back in 1974, the year Knuth's paper was published, in order to better understand the concerns of the author in his paper.

At the end we try to analyze the current state of our industry, specifically around what has been dubbed "Buzzword Oriented Programming", the attitude of judging the merit of technologies based on blog post titles, or the 140 characters of a tweet.

The talk was originally presented at Papers We Love Madrid.

Transcript

1. Harmful GOTO's,
   Premature Optimizations,
   and
   Programming Myths are
   The Root of all Evil
   Alvaro Videla
   

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2. Myths
   

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3. myth: a widely held but false
   belief or idea
   Google define
   

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4. myth: an unproved or false
   collective belief that is used to
   justify a social institution
   dictionary.com
   

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5. The Book of Legendary Lands
   

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6. What it was that Christopher
   Columbus tried to
   demonstrate?
   

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7. A History of the Life and Voyages
   of Christopher Columbus
   

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8. Lactantius - Cosmas Indicopleustes
   

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9. Do we have similar myths in
   Computer Science?
   

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10. Some Myths
    • No Unit-Tests, no working code
    • Procedure calls are expensive
    • NoSQL is faster than traditional DBs
    • 10x Engineers
    • Servers are cheaper than engineers
    

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11. In the beginning…
    

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12. May I ask if there is a reason
    why you prefer using goto
    instead of function recursion?
    https://github.com/igorw/retry/issues/3
    

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13. retry library
    namespace igorw;
    class FailingTooHardException extends \Exception {}
    function retry($retries, callable $fn)
    {
    beginning:
    try {
    return $fn();
    } catch (\Exception $e) {
    if (!$retries) {
    throw new FailingTooHardException('', 0, $e);
    }
    $retries--;
    goto beginning;
    }
    }
    

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14. retry library
    namespace igorw;
    class FailingTooHardException extends \Exception {}
    function retry($retries, callable $fn)
    {
    beginning:
    try {
    return $fn();
    } catch (\Exception $e) {
    if (!$retries) {
    throw new FailingTooHardException('', 0, $e);
    }
    $retries--;
    goto beginning;
    }
    }
    

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15. retry library
    

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16. GOTO flamewar dot gif
    

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17. Go To Statement Considered Harmful
    

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18. GOTO still considered harmful?
    

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19. A case against the goto statement
    +
    Niklaus Wirth
    =
    Go To Statement Considered Harmful
    

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21. Please don't fall into the trap of believing that I am terribly
    dogmatical about [the go to statement]. I have the
    uncomfortable feeling that others are making a religion out
    of it, as if the conceptual problems of programming could
    be solved by a single trick, by a simple form of coding
    discipline!
    E. Dijkstra
    

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22. Please don't fall into the trap of believing that I am terribly
    dogmatical about [the go to statement]. I have the
    uncomfortable feeling that others are making a religion out
    of it, as if the conceptual problems of programming could
    be solved by a single trick, by a simple form of coding
    discipline!
    E. Dijkstra
    

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23. In search of Silver Bullets
    • Microservices
    • Testing
    • Agile
    • Performance Tricks
    • NoSQL
    • Message Queues
    

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24. Beating the CAP
    Theorem
    https://www.youtube.com/watch?v=Wp08EmQtP44#t=1273
    

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25. There is no single development, in either
    technology or management technique, which by
    itself promises even one order of magnitude
    [tenfold] improvement within a decade in
    productivity, in reliability, in simplicity
    Frederick Brooks Jr
    No Silver Bullet - http://worrydream.com/refs/Brooks-NoSilverBullet.pdf
    

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26. Structured programming
    with go to statements
    • Introduction
    • Elimination of Go To Statements
    • Introduction of Go To Statements
    • Conclusions
    

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27. Structured programming
    with go to statements
    

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28. What year is this
    paper from?
    

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29. 1974
    http://www.gregwilson.co.uk/tag/muhammad-ali/
    

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30. http://dl.acm.org/citation.cfm?id=807045&dl=ACM&coll=DL
    

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31. Logic Programming
    http://dspace.mit.edu/handle/1721.1/6171
    http://dl.acm.org/citation.cfm?doid=155360.155362
    1969 1972
    

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32. http://web.archive.org/web/20120716185629/http://www.bitsavers.org/pdf/dartmouth/BASIC_Oct64.pdf
    

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33. 1973: Ethernet & UNIX
    http://www.computerhistory.org/timeline/?year=1973
    

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34. 1976: Big O Notation
    http://www.phil.uu.nl/datastructuren/10-11/knuth_big_omicron.pdf
    

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35. 1976: Big O Notation
    http://www.phil.uu.nl/datastructuren/10-11/knuth_big_omicron.pdf
    

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36. 1977: RSA
    http://www.google.com/patents/US4405829
    

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37. 1978: Type Polymorphism
    https://courses.engr.illinois.edu/cs421/sp2013/project/milner-polymorphism.pdf
    

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38. TL;DR: 1974
    • Almost no personal computers
    • Public Encryption a new thing
    • Structured Programming was all the rage
    • Abstract Data Types a new thing
    

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39. low computer resources
    

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40. “most of the running time in
    non-IO-bound programs is
    concentrated in about 3% of the
    source text”
    D. Knuth
    

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41. “Experience indicates that nearly
    everybody has the wrong idea about
    the real bottlenecks in his programs”
    D. Knuth
    Computer Programming as an Art - http://dl.acm.org/citation.cfm?id=361612
    

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42. “we should forget about small
    efficiencies, say about 97% of
    the time”
    D. Knuth
    

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43. “premature optimization is the
    root of all evil”
    D. Knuth
    

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44. “premature optimization is the
    root of all evil”
    D. Knuth
    The Godwin Law of Optimization Discussions
    

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45. “Yet we should not pass up our opportunities in that
    critical 3%. A good programmer will not be lulled
    into complacency by such reasoning, he will be
    wise to look carefully at the critical code; but only
    after that code has been identified”
    D. Knuth
    

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46. “Yet we should not pass up our opportunities in
    that critical 3%. A good programmer will not be
    lulled into complacency by such reasoning, he will
    be wise to look carefully at the critical code; but
    only after that code has been identified”
    D. Knuth
    

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47. “the universal experience of
    programmers who have been using
    measurement tools has been that their
    intuitive guesses fail”
    D. Knuth
    

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48. more GOTO elimination
    with focus on performance
    and program readability
    

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49. “My books emphasize efficiency
    because they deal with algorithms that
    are used repeatedly as building blocks
    in a large variety of applications”
    D. Knuth
    

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50. “We shouldn't merely remove go to
    statements because it's the fashionable
    thing to do; the presence or absence of
    go to statements is not really the issue.”
    D. Knuth
    

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51. “We shouldn't merely remove go to
    statements because it's the fashionable
    thing to do; the presence or absence of
    go to statements is not really the issue.”
    D. Knuth
    

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52. “The question is whether we
    should ban it [GOTO], or
    educate against it”
    Donald Knuth
    

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53. Cargo Cult Programming
    http://c2.com/cgi/wiki?CargoCult
    

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54. “The biggest problem we have
    as human beings is that we
    confuse our beliefs with reality”
    Alan Kay
    http://www.tele-task.de/archive/video/html5/14029/
    

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55. How did we arrive to this status?
    

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56. Pop Culture
    

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57. “[in the 70s] computing spread out
    much, much faster than educating
    unsophisticated people can happen”
    Alan Kay
    https://queue.acm.org/detail.cfm?id=1039523
    

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58. Twitter/HackerNews
    Oriented Programming
    

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59. http://tinytocs.org/
    

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60. “Those who cannot remember
    the past are condemned to
    repeat it"
    George Santayana
    https://archive.org/stream/lifeofreasonorph01sant#page/284/mode/2up
    

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61. https://archive.org/stream/lifeofreasonorph01sant#page/284/mode/2up
    

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62. History Repeats Itself
    Agile vs. Thinking Forth
    http://thinking-forth.sourceforge.net
    

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63. History Repeats Itself
    TDD
    https://arialdomartini.wordpress.com/2012/07/20/you-wont-believe-how-old-tdd-is/
    You won’t believe how old TDD is
    vs.
    

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64. History Repeats Itself
    offline-first
    http://www.isi.edu/~johnh/RESEARCH/ucla/#ficus_replication
    primarily-disconnected
    vs.
    

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65. “In 1968, the Communications of the ACM published a
    text of mine under the title "The goto statement
    considered harmful", which in later years would be
    most frequently referenced, regrettably, however, often
    by authors who had seen no more of it than its title”
    E. Dijkstra
    https://www.cs.utexas.edu/users/EWD/transcriptions/EWD13xx/EWD1308.html
    

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66. “In 1968, the Communications of the ACM published a
    text of mine under the title "The goto statement
    considered harmful", which in later years would be
    most frequently referenced, regrettably, however, often
    by authors who had seen no more of it than its title”
    E. Dijkstra
    https://www.cs.utexas.edu/users/EWD/transcriptions/EWD13xx/EWD1308.html
    

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67. Fahreinheit 451
    

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68. “Classics cut to fit fifteen-minute radio
    shows, then cut again to fill a two-minute
    book column, winding up at last as a
    ten- or twelve-line dictionary resume”
    Fahrenheit 451
    

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69. Memes
    

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70. “[…] there has been far too much emphasis on go
    to elimination instead of on the really important
    issues; people have a natural tendency to set up all
    easily understood quantitative goal like the
    abolition of jumps, instead of working directly for a
    qualitative goal like good program structure”
    D. Knuth
    

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71. “[…] there has been far too much emphasis on go
    to elimination instead of on the really important
    issues; people have a natural tendency to set up all
    easily understood quantitative goal like the
    abolition of jumps, instead of working directly for a
    qualitative goal like good program structure”
    D. Knuth
    

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72. “we should strive most of all for a
    program that is easy to understand
    and almost sure to work”
    D. Knuth
    

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73. “we had better see to it that
    the computer industry does
    not kill computing science”
    E. Dijkstra
    https://www.cs.utexas.edu/users/EWD/transcriptions/EWD12xx/EWD1284.html
    

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74. Thanks
    Alvaro Videla - @old_sound
    

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