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Should be good for first draft now
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rtoal committed May 24, 2016
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173 changes: 117 additions & 56 deletions index.html
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<head>
<meta charset="utf-8">

<title>A Presentation on Tony Hoare's CSP</title>
<title>A Presentation on Tony Hoare&rsquo;s CSP</title>

<meta name="description" content="CSP">
<meta name="apple-mobile-web-app-capable" content="yes">
Expand Down Expand Up @@ -35,15 +35,15 @@
<div class="slides">
<section data-background="hoare-lecture.png">
<div style="margin-left: 10em">
<p class="dark-shadow">Tony Hoare's</p>
<p class="dark-shadow">Tony Hoare&rsquo;s</p>
<h1 class="dark-shadow" style="font-size:500%;letter-spacing:0.3ex">CSP</h1>
<h3 class="dark-shadow">The Old School<br>Version</h3>
<p class="dark-shadow" style="margin-top:2em">@rtoal</p>
</div>
</section>

<section>
<small>Hi, it's me</small>
<small>Hi, it&rsquo;s me</small>
<p style="margin:1em"><img class="headshot" src="rt.jpg"></p>
<small>I like programming languages</small>
</section>
Expand Down Expand Up @@ -91,9 +91,9 @@ <h2>Why did he write this paper?</h2>
<section data-transition="zoom" data-background="race.jpg">
<h2 class="fragment fade-in"style="color:black;margin-bottom:2.5em;font-size:300%">RACES!</h2>
<ul style="color:black">
<li class="fragment fade-in">Hardware solutions?
<li class="fragment fade-in">Hardware solutions?
<span class="fragment fade-in">Expensive (well it used to be)</span>
<li class="fragment fade-in">Software solutions?
<li class="fragment fade-in">Software solutions?
<span class="fragment fade-in">Semaphores, Mutexes, Atomic Operations,
Monitors, Barriers, Countdowns, OH MY!</span>
</ul>
Expand All @@ -102,7 +102,7 @@ <h2 class="fragment fade-in"style="color:black;margin-bottom:2.5em;font-size:30
<section>
<h2 data-transition="fade">Hoare&rsquo;s Seven Proposals</h2>
<ol>
<li class="fragment fade-in">Parallel command launches procs simultaneously
<li class="fragment fade-in">Parallel command launches procs simultaneously and finishes when all the procs finish
<li class="fragment fade-in">Simple input and output commands
<li class="fragment fade-in">Unbuffered and synchronous on both sides
<li class="fragment fade-in">Guards for nondeterminism
Expand All @@ -118,13 +118,13 @@ <h2 data-transition="fade">Hoare&rsquo;s Seven Proposals</h2>

[west::DISSASEMBLE || X::SQUASH || east::ASSEMBLE]

[ room::ROOM
|| fork(i:0..4)::FORK
[ room::ROOM
|| fork(i:0..4)::FORK
|| phil(i:0..4)::PHIL
]

X :: *[c:character; west?c -> east!c]
</pre>
</pre>
</section>

<section>
Expand Down Expand Up @@ -175,7 +175,9 @@ <h2>Terms</h2>
P()
(x, y)
cons(a,100)
line[80]
</pre>
<div style="margin-top:-1.5em;margin-left:-5em"><small><em>...Hoare used () for arrays but I don&rsquo;t like that.</em></small></div>
</section>

<section>
Expand All @@ -184,7 +186,7 @@ <h2>Expressions</h2>
<li>Unspecified, come from some kind of
host language apparently
<li>But of course we want <code>+</code>, <code>*</code>
<code>=</code>, <code>>=</code>, etc.
<code>=</code>, <code>&gt;</code>, <code>&le;</code>, etc.
<li>Same for types, we should have at least <code>int</code>,
<code>bool</code>, <code>string</code>
</section>
Expand All @@ -206,48 +208,53 @@ <h2><s style="color:#777">Assignments</s> Matching</h2>

<section>
<h2>Input and Output</h2>
<pre style="font-size:26pt">
DIV ! (3*a+b, 13)
X ? (x,y)
console(j-1) ! "A"
console(i) ? c
sem ! P()
X(i) ? V()
</pre>
<small>Wait for each other. Must match. Assigns. Fails if other side already terminated.</small>
<table style="margin:1em auto">
<tr><td><code style="font-size:22pt">DIV ! (3*a+b, 13)</code>
<tr><td><code style="font-size:22pt">X ? (x,y)</code>
<tr><td><code style="font-size:22pt">console(j-1) ! "A"</code>
<tr><td><code style="font-size:22pt">console(i) ? c</code>
<tr><td><code style="font-size:22pt">sem ! P()</code>
<tr><td><code style="font-size:22pt">X(i) ? V()</code>
</table>

<div><small>Wait for each other. Must match. Assigns. Fails if other side already terminated.</small></div>
</section>

<section>
<h2>Guarded Commands</h2>
<pre style="font-size:26pt;margin:1.5em 0">
i &le; 80 -> X!cardimage(i)
(i:0..4)phil(i)?enter() -> diners := diners + 1
x < 5, c := 10, true, y > c -> x := x + 1
</pre>
<div><small>
Execute command list only if guard succeeds<br>
Evaluate guard elements left-to-right<br>
false is fail
</small></div>
<p><small><em>Not a top-level command!</em></small></p>
<table style="margin:1em auto">
<tr><td><code style="font-size:22pt">i &le; 80 -> X!cardimage[i]</code>
<tr><td><code style="font-size:22pt">(i:0..4)phil(i)?enter() -> diners := diners + 1</code>
<tr><td><code style="font-size:22pt">(x &lt; 5, c := 10, true, y > c -> x := x + 1</code>
</table>
<div><small>
Execute command list only if guard succeeds<br>
Evaluate guard elements left-to-right<br>
false is fail
</small></div>
</section>

<section>
<h2>Alternative (Conditional)</h2>
<p style="margin:2em 0">
[ G1 -> CL1 &#x25af; G2 -> CL2 &#x25af; ... &#x25af; Gn -> CLn ]
</p>
<div><small>
Arbitrarily select one of the ready command lists<br>
If all guards fail, the whole command fails
</small></div>
<h2>Alternatives (Choices)</h2>
<table style="margin:1em auto">
<tr><td><code style="font-size:22pt">[ x &ge; y -> m := x &#x25af; y &ge; x -> m := y ]</code>
<tr><td><code style="font-size:22pt">[ c &ne; "*" -> east!c &#x25af; c = "*" -> west?c ]</code>
<tr><td><code style="font-size:22pt">[ i &lt; 124 -> i := i+1<br>&#x25af; i = 125 -> printer!line; i := 1<br>]</code>
</table>
<div><small>
Arbitrarily select one of the ready command lists<br>
If all guards fail, the whole command fails
</small></div>
</section>

<section>
<h2>Repetition (Loop)</h2>
<pre>
...

</pre>
<h2>Repetitives (Loops)</h2>
<table style="margin:1em auto">
<tr><td><code style="font-size:22pt">*[i &le; 80 -> X!card]</code>
<tr><td><code style="font-size:22pt">*[X?V() -> val := val+1<br>&#x25af; val > 0; Y?P() -> val := val-1<br>]</code>
<tr><td><code style="font-size:22pt"></code>
</table>
<div><small>
Loop as long as at least one guard succeeds<br>
If all guards fail, the loop exits cleanly
Expand All @@ -256,31 +263,84 @@ <h2>Repetition (Loop)</h2>


<section>
<p>TODO EXAMPLE</p>
</section>

<section>
<p>TODO EXAMPLE</p>
<h2>Example: Division (slow)</h2>
<pre><code>
[ DIV :: *[x,y: integer, X?(x,y) ->
quot, rem: integer; quot := 0; rem := x;
*[ rem &ge; y -> rem := rem - y; quot := quot + 1 ];
X!(quot, rem)
]
||
X :: USER
]
</code></pre>
</section>


<section>
<p>TODO EXAMPLE</p>
<h2>Example: Factorial</h2>
<pre><code>
[ fac(i:1..limit) ::
*[n: integer, fac(i-1)?n ->
[ n = 0 -> fac(i-1)!1
&#x25af; n > 0 -> fac(i+1)!n-1;
r:integer; fac(i+1)?r;
fac(i-1)!(n*r)
]
]
||
fac(0) :: USER
]
</code></pre>
<div><img src="factorial-chain.png"></div>
</section>


<section>
<p>TODO EXAMPLE</p>
<h2>Example: Buffer (as a Process)</h2>
<pre><code>
Q ::
buffer: [0..9]object;
in, out: integer; in := 0; out := 0;

*[ in < out+10; producer?buffer[in mod 10] ->
in := in+1

&#x25af; out < in; consumer?more() ->
consumer!buffer[out mod 10];
out := out + 1
]
</code></pre>
<div><small>producer invokes <code>Q!obj</code><br>consumer invokes <code>Q!more(); Q?obj</code></small></div>
</section>


<section>
<p>TODO EXAMPLE</p>
<h2>Example: Dining Philosophers</h2>
<div><small>(Deadlock possible)</small></div>
<pre><code>
[room::ROOM || fork(i:0..4)::FORK || phil(i:0..4)::PHIL]

where ROOM =
diners: integer; diners := 0;
*[ (i:0..4)phil(i)?enter() -> diners := diners + 1
&#x25af; (i:0..4)phil(i)?exit() -> diners := diners - 1
]

and FORK =
*[ phil(i)?pickup() -> phil(i)?putdown()
&#x25af; phil(i-1 mod 5)?pickup() -> phil(i-1 mod 5)?putdown()
]

and PHIL =
*[ THINK;
room?enter();
fork(i)!pickup(); fork(i+1 mod 5)!pickup();
EAT;
fork(i)!putdown(); fork(i+1 mod 5)!putdown();
room!exit()
]
</code></pre>
</section>



<section>
<section data-background="darkgreen">
<h2>Hoare&rsquo;s Suggestion</h2>
<p>Concurrency and communication should be regarded as
primitives of programming (not unlike assignment,
Expand All @@ -290,6 +350,7 @@ <h2>Hoare&rsquo;s Suggestion</h2>

<section>
<h2>So...Who uses this stuff today?</h2>
<p><img src="xkcd-win7.png" height=300 style="border:none"></p>
</section>

<section data-transition="zoom">
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