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diff --git a/doc/talks/go_talk-20100323.html b/doc/talks/go_talk-20100323.html new file mode 100644 index 000000000..3143b079a --- /dev/null +++ b/doc/talks/go_talk-20100323.html @@ -0,0 +1,395 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> +<head> +<title>Go Tech Talk</title> +<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> +<meta name="font-size-adjustment" content="-1" /> +<link rel="stylesheet" href="slidy.css" + type="text/css" media="screen, projection, print" /> +<script src="slidy.js" type="text/javascript"> +</script> +</head> +<body> +<!-- this defines the slide background --> + +<div class="background"> + + <div class="header"> + <!-- sized and colored via CSS --> + </div> + + <div class="footer"></div> + </div> + +<div class="slide titlepage"> +<br/> +<br/> +<img src="../go-logo-white.png" width="588px" height="217px"> +<br/> +<h1 style="padding-right: 0pt; margin-right: 0pt; color: #0066cc; font-size: 250%; border-bottom: 0px;">The Go Programming Language</h1> +<div style="color: #ffcc00;"> +<br/> +<h3>Sydney University<br/><br/>March 23, 2010</h3> +</div> +</div> + +<div class="slide"> + <h1>Go</h1> + + <h2>New</h2> + <h2>Experimental</h2> + <h2>Concurrent</h2> + <h2>Garbage Collected</h2> + <h2>Systems Language</h2> +</div> + +<div class="slide"> + <h1>Hello, world</h1> +<pre> +package main + +import "fmt" + +func main() { + fmt.Printf("Hello, 世界\n") +} +</pre> +</div> + +<div class="slide"> + <h1>Hello, world 2.0</h1> + + <h2>Serving <a href="http://localhost:8080/world">http://localhost:8080/world</a></h2> +<pre> +package main + +import ( + "fmt" + "http" +) + +func handler(c *http.Conn, r *http.Request) { + fmt.Fprintf(c, "Hello, %s.", r.URL.Path[1:]) +} + +func main() { + http.ListenAndServe(":8080", + http.HandlerFunc(handler)) +} +</pre> +</div> + +<div class="slide"> + <h1>New</h1> + + <h2>It's about two years old:</h2> + <ul> + <li>Design started in late 2007</li> + <li>Implementation starting to work mid-2008</li> + <li>Released as an open source project in November 2009</li> + <li>Development continues with an active community</li> + </ul> + + <h2>Why invent a new language? Older languages weren't designed for concurrency, but modern software needs it:</h2> + <ul> + <li>Large scale, networked computing, such as Google web search</li> + <li>Multi-core hardware</li> + </ul> +</div> + +<div class="slide"> + <h1>New</h1> + + <h2>Older languages are also frustrating on a day-to-day basis</h2> + <h2>Statically-typed languages (C, C++, Java) have issues:</h2> + <ul> + <li>Edit-Compile-Run cycle takes far too long</li> + <li>Type hierarchy can hurt as much as it helps</li> + </ul> +<div style="text-align:center"> +<img src="java-typing.png" width="800px" height="90px"><br> +</div> + + <h2>Dynamic languages (Python, JavaScript) fix some issues but introduce others:</h2> + <ul> + <li>No compilation means slow code</li> + <li>Runtime errors that should be caught statically</li> + </ul> + + <h2>Go has the lighter feel of a scripting language but is compiled</h2> +</div> + +<div class="slide"> + <h1>New</h1> + + <h2>Large C++ programs (e.g. Firefox, OpenOffice, Chromium) have enormous build times:</h2> + <ul> + <li>XKCD's #1 Programmer Excuse for Legitimately Slacking Off: "<a href="http://xkcd.com/303/">My Code's Compiling</a>"</li> + </ul> + + <h2>On a Mac (OS X 10.5.8, gcc 4.0.1):</h2> + <ul> + <li>C: <code>#include <stdio.h></code> reads 360 lines from 9 files</li> + <li>C++: <code>#include <iostream></code> reads 25,326 lines from 131 files</li> + <li>Objective-C: <code>#include <Carbon/Carbon.h></code> reads 124,730 lines from 689 files</li> + <li>We haven't done any real work yet!</li> + </ul> + + <h2>In Go: <code>import "fmt"</code> reads <i>one</i> file: 184 lines summarizing 7 packages</h2> +</div> + +<div class="slide"> + <h1>New</h1> + + <h2>Compilation demo</h2> +</div> + +<div class="slide"> + <h1>Experimental</h1> + + <h2>Go is still unproven</h2> + <h2>Language is still evolving</h2> + <h2>Package library is incomplete</h2> + <h2>Concurrent garbage collection is an active research problem</h2> + <h2>Reviving forgotten concepts:</h2> + <ul> + <li>Go's concurrency is strongly influenced by <i>Communicating Sequential Processes</i> (Hoare, 1978)</li> + <li>Go has types and interfaces, but no inheritance. It is arguably more object-oriented than previously mentioned languages, being closer to the original Smalltalk meaning (1970s)</li> + </ul> +</div> + +<div class="slide"> + <h1>Concurrent</h1> + + <h2>Unix philosophy: write <i>programs</i> that do one thing and do it well</h2> + <h2>Connect them with <i>pipes</i>:</h2> + <ul> + <li>How many lines of test code are there in the Go standard library?</li> + <li><code>find ~/go/src/pkg | grep _test.go$ | xargs wc -l</code></li> + </ul> + + <h2>Unlike other languages, Go makes it easy to:</h2> + <ul> + <li>Launch <i>goroutines</i></li> + <li>Connect them with <i>channels</i></li> + </ul> +</div> + +<div class="slide"> + <h1>Concurrent</h1> + + <h2>Start a new flow of control with the <code>go</code> keyword</h2> + <h2>Parallel computation is easy:</h2> +<pre> +func main() { + go expensiveComputation(x, y, z) + anotherExpensiveComputation(a, b, c) +} +</pre> + + <h2>Roughly speaking, a goroutine is like a thread, but lighter weight:</h2> + <ul> + <li>Goroutines have segmented stacks, and typically smaller stacks</li> + <li>This requires compiler support. Goroutines can't just be a C++ library on top of a thread library</li> + </ul> +</div> + +<div class="slide"> + <h1>Concurrent</h1> + + <h2>Consider web servers ("the C10k problem"):</h2> + <ul> + <li>"Thread per connection" approach is conceptually neat, but doesn't scale well in practice</li> + <li>What does scale well (event-driven callbacks, asynchronous APIs) are harder to understand, maintain, and debug</li> + <li>We think "goroutine per connection" can scale well, and is conceptually neat</li> + </ul> +<pre> + for { + rw := socket.Accept() + conn := newConn(rw, handler) + go conn.serve() + } +</pre> +</div> + +<div class="slide"> + <h1>Concurrent</h1> + + <h2>Let's look again at our simple parallel computation:</h2> +<pre> +func main() { + go expensiveComputation(x, y, z) + anotherExpensiveComputation(a, b, c) +} +</pre> + + <h2>This story is incomplete:</h2> + <ul> + <li>How do we know when the two computations are done?</li> + <li>What are their values?</li> + </ul> +</div> + +<div class="slide"> + <h1>Concurrent</h1> + + <h2>Goroutines communicate with other goroutines via channels</h2> +<pre> +func computeAndSend(ch chan int, x, y, z int) { + ch <- expensiveComputation(x, y, z) +} + +func main() { + ch := make(chan int) + go computeAndSend(ch, x, y, z) + v2 := anotherExpensiveComputation(a, b, c) + v1 := <-ch + fmt.Println(v1, v2) +} +</pre> + +</div> + +<div class="slide"> + <h1>Concurrent</h1> + + <h2>In traditional concurrent programs, you <i>communicate by sharing memory</i>. In Go, you <i>share memory by communicating</i>:</h2> + <ul> + <li>Communication (the <code><-</code> operator) is sharing and synchronization</li> + </ul> + + <h2>Threads and locks are concurrency primitives; CSP is a concurrency model:</h2> + <ul> + <li>Analogy: "Go To Statement Considered Harmful" (Dijsktra, 1968)</li> + <li><code>goto</code> is a control flow primitive; structured programming (<code>if</code> statements, <code>for</code> loops, function calls) is a control flow model</li> + </ul> + + <h2>Learning CSP changes the way you think about concurrent programming:</h2> + <ul> + <li>Every language has its grain. If your Go program uses mutexes, you're probably working against the grain</li> + </ul> +</div> + +<div class="slide"> + <h1>Garbage Collected</h1> + + <h2>Automatic memory management makes writing (and maintaining) programs easier</h2> + <h2>Especially in a concurrent world:</h2> + <ul> + <li>Who "owns" a shared piece of memory, and is responsible for destroying it?</li> + </ul> + + <h2>Large C++ programs usually end up with semi-automatic memory management anyway, via "smart pointers"</h2> + <h2>Mixing the two models can be problematic:</h2> + <ul> + <li>Browsers can leak memory easily; DOM elements are C++ objects, but JavaScript is garbage collected</li> + </ul> +</div> + +<div class="slide"> + <h1>Garbage Collected</h1> + + <h2>Go is also a safer language:</h2> + <ul> + <li>Pointers but no pointer arithmetic</li> + <li>No dangling pointers</li> + <li>Variables are zero-initialized</li> + <li>Array access is bounds-checked</li> + </ul> + + <h2>No buffer overflow exploits</h2> +</div> + +<div class="slide"> + <h1>Systems Language</h1> + + <h2>This just means you could write decently large programs in Go:</h2> + <ul> + <li>Web servers</li> + <li>Web browsers</li> + <li>Web crawlers</li> + <li>Search indexers</li> + <li>Databases</li> + <li>Word processors</li> + <li>Integrated Development Environments (IDEs)</li> + <li>Operating systems</li> + <li>...</li> + </ul> +</div> + +<div class="slide"> + <h1>Systems Language</h1> + + <h2>Garbage collection has a reputation for being "slower"</h2> + <h2>We're expecting Go to be slightly slower than optimized C, but faster than Java, depending on the task. Nonetheless:</h2> + <ul> + <li>Fast and buggy is worse than almost-as-fast and correct</li> + <li>It is easier to optimize a correct program than to correct an optimized program</li> + <li>Fundamentally, it's simply a trade-off we're willing to make</li> + </ul> + + <h2>Memory layout can drastically affect performance. These two designs are equivalent in Go, but significantly different in Java:</h2> +<pre> +type Point struct { X, Y int } +type Rect struct { P0, P1 Point } + +// or ... + +type Rect struct { X0, Y0, X1, Y1 int } +</pre> +</div> + +<div class="slide"> + <h1>Systems Language</h1> + + <h2>Quote from http://loadcode.blogspot.com/2009/12/go-vs-java.html</h2> + +<h2> +"[Git] is known to be very fast. It is written in C. A Java version +JGit was made. It was considerably slower. Handling of memory and lack +of unsigned types was some of the important reasons. +</h2> + +<h2>Shawn O. Pearce wrote on the git mailinglist:</h2> +<ul><li>"JGit struggles with not +having an efficient way to represent a SHA-1. C can just say "unsigned +char[20]" and have it inline into the container's memory allocation. A +byte[20] in Java will cost an *additional* 16 bytes of memory, and be +slower to access because the bytes themselves are in a different area +of memory from the container object. We try to work around it by +converting from a byte[20] to 5 ints, but that costs us machine +instructions" +</li></ul> + +<h2> +Like C, Go does allow unsigned types and defining data structures +containing other data structures as continuous blocks of memory." +</h2> +</div> + +<div class="slide"> + <h1>Go</h1> + + <h2>New</h2> + <h2>Experimental</h2> + <h2>Concurrent</h2> + <h2>Garbage Collected</h2> + <h2>Systems Language</h2> + + <h2>And more:</h2> + <ul> + <li>I haven't talked about the type system, interfaces, slices, closures, selects, ...</li> + <li>Tutorial, documentation, mailing list, source code all online</li> + </ul> +</div> + +<div class="slide titlepage"> + <h1>Questions?</h1> + <br><br> + <center> + <img src="../gordon/bumper640x360.png" width="640px" height="360px"> + </center> +</div> + +</body></html> |