Guy Steele on Parallel Programing

Discussion in 'Python' started by Xah Lee, Feb 5, 2011.

  1. Xah Lee

    Xah Lee Guest

    might be interesting.

    〈Guy Steele on Parallel Programing〉
    http://xahlee.org/comp/Guy_Steele_parallel_computing.html

    --------------------------------------------------

    Guy Steele on Parallel Programing

    Xah Lee, 2011-02-05

    A fascinating talk by the well respected computer scientist Guy
    Steele. (famously known as one of the author of Scheme Lisp)

    How to Think about Parallel Programming: Not! (2011-01-14) By Guy
    Steele. @ http://www.infoq.com/presentations/Thinking-Parallel-Programming

    The talk is a bit long, at 70 minutes. The first 26 minutes he goes
    thru 2 computer programs written for 1970's machines. It's quite
    interesting to see how software on punch card works. For most of us,
    we never seen a punch card. He actually goes thru it “line by lineâ€,
    actually “hole by holeâ€. Watching it, it gives you a sense of how
    computers are like in the 1970s.

    At 00:27, he starts talking about “automating resource managementâ€,
    and quickly to the main point of his talk, as in the title, about what
    sort of programing paradigms that are good for parallel programing.
    Here, parallel programing means solving a problem by utilizing
    multiple CPU or nodes (as in clusters or grid). This is important
    today, because CPU don't get much faster anymore; instead, each our
    computer are getting more CPU (multi-core).

    In the rest 40 min of the talk, he steps thru 2 programs that solves a
    simple problem of splitting a sentence into words. First program is
    typical sequential style, using do-loop (accumulator). The second
    program is written in his language Fortress, using functional style.
    He then summarizes a few key problems with traditional programing
    patterns, and introduces a few critical programing patterns that he
    thinks is critical for programing languages to automate parallel
    computing.

    In summary, as a premise, he believes that programers should not worry
    about parallelism at all, but the programing language should
    automatically do it. Then, he illustrates that there are few
    programing patterns that we must stop using, because if you do write
    your code in such paradigm, then it would be very hard to parallelize
    the code, either manually or by machine AI.

    If you are a functional programer and read FP news in the last couple
    of years, his talk doesn't cover much new. However, i find it very
    interesting, because:

    * â‘  This is the first time i see Guy Steele talk. He talks
    slightly fast. Very bright guy.
    * â‘¡ The detailed discussion of punch card code on 1970's machine
    is quite a eye-opener for those of us who's not in that era.
    * â‘¢ You get to see Fortress code, and its use of fancy unicode
    chars.
    * â‘£ Thru the latter half of talk, you get a concrete sense of some
    critical “do's & don'ts†in coding paradigms about what makes
    automated parallel programing possible or impossible.

    In much of 2000s, i did not understand why compilers couldn't just
    automatically do parallelism. I thought about it in 2009, and realized
    why. See: Why Must Software Be Rewritten For Multi-Core Processors?.

    --------------------
    Parallel Computing vs Concurrency Problems

    Note that parallel programing and concurrency problem are not the same
    thing.

    Parallel programing is about writing code that can use multiple CPU.
    Concurrency problems is about problems of concurrent computations
    using the same resource or time (e.g. race condition, file locking).
    See: Parallel computing â—‡ Concurrency (computer science)

    --------------------
    Fortress & Unicode

    It's interesting that Fortress language freely uses unicode chars. For
    example, list delimiters are not the typical {} or [], but the unicode
    angle bracket 〈〉. (See: Matching Brackets in Unicode.) It also uses
    the circle plus ⊕ as operator. (See: Math Symbols in Unicode.)

    I really appreciate such use of unicode. The tradition of sticking to
    the 95 chars in ASCII of 1960s is extremely limiting. It creates
    complex problems manifested in:

    * String Escape mechanism (C's “\nâ€, widely adopted.)

    * Complex delimiters (Python's triple quotes and perl's variable
    delimiters q() q[] q{} m//, and heredoc. (See: Strings in Perl and
    Python â—‡ Heredoc mechanism in PHP and Perl.)

    * Crazy leaning toothpick syndrome, especially bad in emacs regex.

    * Complexities in character representation (See: Emacs's Key
    Notations Explained (/r, ^M, C-m, RET, <return>, M-, meta) â—‡ HTML
    entities problems. See: HTML Entities, Ampersand, Unicode, Semantics.)

    * URL Percent Encoding problems and complexities: Javascript
    Encode URL, Escape String

    All these problems occur because we are jamming so many meanings into
    about 20 symbols in ASCII.

    See also:

    * Computer Language Design: Strings Syntax
    * HTML6: Your JSON and SXML Simplified

    Was this page useful to you?

    Also, almost all of today's languages do not support unicode in
    function or variable names, so you can forget about using unicode in
    variable names (e.g. α=3) or function names (e.g. “lambda†as “λ†or
    “function†as “ƒâ€), or defining your own operators (e.g. “⊕â€).
    (Exceptions i know works well in practice are: Mathematica,
    Javascript, Java, Emacs Lisp. See: Unicode Support in Ruby, Perl,
    Python, Emacs Lisp.)

    Xah ∑ http://xahlee.org/
    Xah Lee, Feb 5, 2011
    #1
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  2. Xah Lee

    Rui Maciel Guest

    Rui Maciel, Feb 5, 2011
    #2
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