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+<title>Go, Networked (January 21, 2010)</title>
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+
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+<br/>
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+<br/>
+<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;">
+<h2>Russ Cox</h2>
+<!-- <h3><i>rsc@google.com</i></h3> -->
+<br/>
+<h3>CNS Winter Research Review<br/><br/>January 21, 2010</h3>
+<br/>
+<br/>
+<!--
+<h4><i>click to start; then left/right arrow to change slides</i></h4> -->
+</div>
+</div>
+
+<div class="slide">
+ <h1>Go</h1>
+
+ <h2>New</h2>
+ <h2>Experimental</h2>
+ <h2>Concurrent</h2>
+ <h2>Garbage-collected</h2>
+ <h2>Systems</h2>
+ <h2>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>History</h1>
+
+ <h2>Design started in late 2007.</h2>
+ <h2>Implementation starting to work mid-2008.</h2>
+ <h2>Released as an open source project in November 2009.</h2>
+ <h2>Work continues.<h2>
+ <h2>Robert Griesemer, Ken Thompson, Rob Pike, Ian Lance Taylor, Russ Cox, many others</h2>
+</div>
+
+<div class="slide">
+ <h1>Goals and Motivation</h1>
+
+ <h2>Go fast!</h2>
+ <h2>Make programming fun again.</h2>
+ <h2>Targeted at systems software, broadly.</h2>
+</div>
+
+<div class="slide">
+ <h1>Why isn't programming fun?</h1>
+
+ <div class="incremental">
+ <h2>Compiled, statically-typed languages (C, C++, Java) require too much typing and too much typing:</h2>
+
+ <ul>
+ <li>verbose, lots of repetition</li>
+ <li>too much focus on type hierarchy</li>
+ <li>types get in the way as much as they help</li>
+ <li>compiles take far too long</li>
+ </ul>
+ </div>
+
+ <div class="incremental">
+ <h2>Dynamic languages (Python, JavaScript) fix these problems (no more types, no more compiler) but introduce others:</h2>
+
+ <ul>
+ <li>errors at run time that should be caught statically</li>
+ <li>no compilation means slow code</li>
+ </ul>
+ </div>
+
+ <h2 class="incremental">Can we combine the best of both?</h2>
+</div>
+
+<div class="slide">
+ <h1>Why a new language?</h1>
+
+ <div class="incremental">
+ <h2>No new systems language in 10+ years.</h2>
+ <h2>Current languages designed before ...</h2>
+ <h3>... rise of large-scale, networked and multicore computing</h3>
+ <h3>... rise of Internet-scale distributed development (many libraries)</h3>
+ </div>
+</div>
+
+<div class="slide">
+ <h1>Go</h1>
+
+ <h2>Make the language fast.</h2>
+ <h2>Make the tools fast.</h2>
+</div>
+
+<div class="slide">
+ <h1>Compilation Demo</h1>
+
+ <h2>Build all standard Go packages: ~120,000 lines of code.</h2>
+</div>
+
+<div class="slide">
+ <h1>Go in one slide</h1>
+
+ <h2 class="incremental">Lightweight syntax.</h2>
+
+ <h2 class="incremental">Static types: enough to compile well, but inferred much of the time.</h2>
+
+ <h2 class="incremental">Methods: on any type, orthogonal to type system.</h2>
+
+ <h2 class="incremental">Abstract types: interface values, relations inferred statically.</h2>
+
+ <h2 class="incremental">Visibility: inferred from case of name.</h2>
+
+ <h2 class="incremental">First-class functions.</h2>
+
+ <h2 class="incremental">Garbage collection.</h2>
+
+ <br/>
+
+ <h2 class="incremental">Lightweight feel of a scripting language but compiled.</h2>
+</div>
+
+<div class="slide">
+ <h1>Go, concurrently</h1>
+
+ <h2>Cheap to create a new flow of control (goroutine):</h2>
+
+<pre>
+func main() {
+ go expensiveComputation(x, y, z)
+ anotherExpensiveComputation(a, b, c)
+}
+</pre>
+
+ <h2>Two expensive computations in parallel.</h2>
+</div>
+
+<div class="slide">
+ <h1>Go, concurrently</h1>
+
+ <h2>Cheap to create a new flow of control (goroutine):</h2>
+
+<pre>
+ for {
+ rw := l.Accept()
+ conn := newConn(rw, handler)
+ go conn.serve()
+ }
+</pre>
+
+ <h2>Concurrent web server.</h2>
+ <h2>Network connections multiplexed onto epoll.</h2>
+ <ul>
+ <li>many blocked Read calls != many blocked OS threads</li>
+ </ul>
+
+</div>
+
+<div class="slide">
+ <h1>Go, synchronized</h1>
+
+ <h2>Use explicit messages to communicate and synchronize.</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>
+ <h2>Notice communication of result in addition to synchronization.</h2>
+</div>
+
+<div class="slide">
+ <h1>Go, synchronized</h1>
+
+ <h2>RPC client</h2>
+
+<pre>
+func (client *Client) Call(method string, args, reply interface{}) os.Error {
+ // Send RPC message.
+ call := client.Go(method, args, reply, nil)
+
+ // Read reply from Done channel.
+ <-call.Done
+
+ return call.Error
+}
+</pre>
+</div>
+
+<div class="slide">
+ <h1>Go, synchronized</h1>
+
+ <h2>RPC client demux</h2>
+
+<pre>
+func (client *Client) input() {
+ for {
+ resp := client.readResponse()
+ client.mutex.Lock()
+ c := client.pending[resp.Seq]
+ client.pending[resp.Seq] = c, false
+ client.mutex.Unlock()
+ if resp.Error != "" {
+ c.Error = os.ErrorString(resp.error)
+ }
+ resp.Decode(c.Reply)
+ c.Done <- c
+ }
+}
+</pre>
+</div>
+
+<div class="slide">
+ <h1>Go, synchronized</h1>
+
+ <h2>RPC client demux</h2>
+
+<pre>
+func (client *Client) input() {
+ for {
+ <font style="color: black;">resp := client.readResponse()</font>
+ client.mutex.Lock()
+ c := client.pending[resp.Seq]
+ client.pending[resp.Seq] = c, false
+ client.mutex.Unlock()
+ if resp.Error != "" {
+ c.Error = os.ErrorString(resp.error)
+ }
+ resp.Decode(c.Reply)
+ c.Done <- c
+ }
+}
+</pre>
+<h2>Read response from network.</h2
+</div>
+
+<div class="slide">
+ <h1>Go, synchronized</h1>
+
+ <h2>RPC client demux</h2>
+
+<pre>
+func (client *Client) input() {
+ for {
+ resp := client.readResponse()
+ <font style="color: black;">client.mutex.Lock()
+ c := client.pending[resp.Seq]
+ client.pending[resp.Seq] = c, false
+ client.mutex.Unlock()</font>
+ if resp.Error != "" {
+ c.Error = os.ErrorString(resp.error)
+ }
+ resp.Decode(c.Reply)
+ c.Done <- c
+ }
+}
+</pre>
+<h2>Look up request by sequence number.</h2
+</div>
+
+<div class="slide">
+ <h1>Go, synchronized</h1>
+
+ <h2>RPC client demux</h2>
+
+<pre>
+func (client *Client) input() {
+ for {
+ resp := client.readResponse()
+ client.mutex.Lock()
+ c := client.pending[resp.Seq]
+ client.pending[resp.Seq] = c, false
+ client.mutex.Unlock()
+ <font style="color: black;">if resp.Error != "" {
+ c.Error = os.ErrorString(resp.error)
+ }
+ resp.Decode(c.Reply)</font>
+ c.Done <- c
+ }
+}
+</pre>
+<h2>Decode response fields from payload.</h2
+</div>
+
+<div class="slide">
+ <h1>Go, synchronized</h1>
+
+ <h2>RPC client demux</h2>
+
+<pre>
+func (client *Client) input() {
+ for {
+ resp := client.readResponse()
+ client.mutex.Lock()
+ c := client.pending[resp.Seq]
+ client.pending[resp.Seq] = c, false
+ client.mutex.Unlock()
+ if resp.Error != "" {
+ c.Error = os.ErrorString(resp.error)
+ }
+ resp.Decode(c.Reply)
+ <font style="color: black;">c.Done <- c</font>
+ }
+}
+</pre>
+<h2>Tell client that it finished.</h2
+</div>
+
+<div class="slide">
+ <h1>Go, synchronized</h1>
+
+ <h2>RPC client demux</h2>
+
+<pre>
+func (client *Client) input() {
+ for {
+ resp := client.readResponse()
+ client.mutex.Lock()
+ c := client.pending[resp.Seq]
+ client.pending[resp.Seq] = c, false
+ client.mutex.Unlock()
+ if resp.Error != "" {
+ c.Error = os.ErrorString(resp.error)
+ }
+ resp.Decode(c.Reply)
+ c.Done <- c
+ }
+}
+</pre>
+
+<h2>Can create multiple Calls with same Done channel
+and distinguish which finished by inspecting value sent on channel.
+</h2>
+
+</div>
+
+<div class="slide">
+ <h1>Goroutine demo</h1>
+
+ <h2>Chain together 100,000 goroutines connected by 100,001 channels.</h2>
+
+ <h2>Send a value to one end of the chain.</h2>
+
+ <h2>Each passes it along, increments.</h2>
+
+ <h2>Receive value out the other end of the chain.</h2>
+</div>
+
+
+<div class="slide">
+ <h1>Go Status</h1>
+</div>
+
+<div class="slide">
+ <h1>Go Status</h1>
+
+ <h2>Open source:</h2>
+ <ul>
+ <li>released on November 10, 2009
+ <li>regular releases (~ weekly)
+ <li>all development done in public Mercurial repository
+ <li>outside contributions welcome
+ <li>two independent compiler implementations
+ <li>XML, JSON, HTTP, TLS/SSL, native RPC, (network channels,) ...
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Go Status</h1>
+
+ <h2>Open source</h2>
+
+ <h2>Portable:</h2>
+ <ul>
+ <li>FreeBSD, Linux, OS X (x86, x86-64)
+ <li>(in progress) Linux arm, Native Client x86, Windows x86.
+ </ul>
+</div>
+
+<div class="slide">
+ <h1>Go Status</h1>
+
+ <h2>Open source</h2>
+ <h2>Portable</h2>
+
+ <h2>Still in progress, experimental. Yet to come:</h2>
+ <ul>
+ <li>production garbage collector
+ <li>generics?
+ <li>exceptions?
+ <li>unions or sum types?
+ </ul>
+</div>
+
+<div class="slide titlepage">
+ <h1>Questions?</h1>
+ <br><br>
+ <center>
+ <img src="../gordon/bumper640x360.png">
+ </center>
+ <br><br>
+ <div style="color: #ffcc00;">
+ <!-- <h3><i>rsc@google.com</i></h3> -->
+ </div>
+</div>
+
+</body></html>