2812

author: Kartik K. Agaram <vc@akkartik.com> 2016-03-26 23:59:59 -0700
committer: Kartik K. Agaram <vc@akkartik.com> 2016-03-27 17:43:41 -0700
commit: a654e4ecace2d506d1b10f1dde2c287ebe84ef37 (patch)
tree: 1e34a3ad99a56e32bdf9ee03ecfe7d339e7942ae /html/078hash.cc.html
parent: 859f35fbe2f6a78157b875e12eb7dc8cd95c1152 (diff)
download: mu-a654e4ecace2d506d1b10f1dde2c287ebe84ef37.tar.gz
1 files changed, 431 insertions, 0 deletions
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+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
+<html>
+<head>
+<meta http-equiv="content-type" content="text/html; charset=UTF-8">
+<title>Mu - 078hash.cc</title>
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+.cSpecial { color: #008000; }
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+<body>
+<pre id='vimCodeElement'>
+<span class="Comment">// A universal hash function that can handle objects of any type.</span>
+<span class="Comment">//</span>
+<span class="Comment">// The way it's currently implemented, two objects will have the same hash if</span>
+<span class="Comment">// all their non-address fields (all the way down) expand to the same sequence</span>
+<span class="Comment">// of scalar values. In particular, a container with all zero addresses hashes</span>
+<span class="Comment">// to 0. Hopefully this won't be an issue because we are usually hashing</span>
+<span class="Comment">// objects of a single type in any given hash table.</span>
+<span class="Comment">//</span>
+<span class="Comment">// Based on <a href="http://burtleburtle.net/bob/hash/hashfaq.html">http://burtleburtle.net/bob/hash/hashfaq.html</a></span>
+
+<span class="Delimiter">:(before &quot;End Primitive Recipe Declarations&quot;)</span>
+HASH<span class="Delimiter">,</span>
+<span class="Delimiter">:(before &quot;End Primitive Recipe Numbers&quot;)</span>
+put<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;hash&quot;</span><span class="Delimiter">,</span> HASH<span class="Delimiter">);</span>
+<span class="Delimiter">:(before &quot;End Primitive Recipe Checks&quot;)</span>
+<span class="Normal">case</span> HASH: <span class="Delimiter">{</span>
+  <span class="Normal">if</span> <span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">)</span> != <span class="Constant">1</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    raise &lt;&lt; maybe<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;'hash' takes exactly one ingredient rather than '&quot;</span> &lt;&lt; to_original_string<span class="Delimiter">(</span>inst<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
+    <span class="Identifier">break</span><span class="Delimiter">;</span>
+  <span class="Delimiter">}</span>
+  <span class="Identifier">break</span><span class="Delimiter">;</span>
+<span class="Delimiter">}</span>
+<span class="Delimiter">:(before &quot;End Primitive Recipe Implementations&quot;)</span>
+<span class="Normal">case</span> HASH: <span class="Delimiter">{</span>
+  reagent input = current_instruction<span class="Delimiter">().</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>  <span class="Comment">// copy</span>
+  products<span class="Delimiter">.</span>resize<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">);</span>
+  products<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>push_back<span class="Delimiter">(</span>hash<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">,</span> input<span class="Delimiter">));</span>
+  <span class="Identifier">break</span><span class="Delimiter">;</span>
+<span class="Delimiter">}</span>
+
+<span class="Comment">//: in all the code below, the intermediate results of hashing are threaded through 'h'</span>
+
+<span class="Delimiter">:(code)</span>
+<span class="Normal">size_t</span> hash<span class="Delimiter">(</span><span class="Normal">size_t</span> h<span class="Delimiter">,</span> reagent&amp; r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  canonize<span class="Delimiter">(</span>r<span class="Delimiter">);</span>
+  <span class="Normal">if</span> <span class="Delimiter">(</span>is_mu_string<span class="Delimiter">(</span>r<span class="Delimiter">))</span>  <span class="Comment">// optimization</span>
+    <span class="Identifier">return</span> hash_mu_string<span class="Delimiter">(</span>h<span class="Delimiter">,</span> r<span class="Delimiter">);</span>
+  <span class="Normal">else</span> <span class="Normal">if</span> <span class="Delimiter">(</span>is_mu_address<span class="Delimiter">(</span>r<span class="Delimiter">))</span>
+    <span class="Identifier">return</span> hash_mu_address<span class="Delimiter">(</span>h<span class="Delimiter">,</span> r<span class="Delimiter">);</span>
+  <span class="Normal">else</span> <span class="Normal">if</span> <span class="Delimiter">(</span>is_mu_scalar<span class="Delimiter">(</span>r<span class="Delimiter">))</span>
+    <span class="Identifier">return</span> hash_mu_scalar<span class="Delimiter">(</span>h<span class="Delimiter">,</span> r<span class="Delimiter">);</span>
+  <span class="Normal">else</span> <span class="Normal">if</span> <span class="Delimiter">(</span>is_mu_array<span class="Delimiter">(</span>r<span class="Delimiter">))</span>
+    <span class="Identifier">return</span> hash_mu_array<span class="Delimiter">(</span>h<span class="Delimiter">,</span> r<span class="Delimiter">);</span>
+  <span class="Normal">else</span> <span class="Normal">if</span> <span class="Delimiter">(</span>is_mu_container<span class="Delimiter">(</span>r<span class="Delimiter">))</span>
+    <span class="Identifier">return</span> hash_mu_container<span class="Delimiter">(</span>h<span class="Delimiter">,</span> r<span class="Delimiter">);</span>
+  <span class="Normal">else</span> <span class="Normal">if</span> <span class="Delimiter">(</span>is_mu_exclusive_container<span class="Delimiter">(</span>r<span class="Delimiter">))</span>
+    <span class="Identifier">return</span> hash_mu_exclusive_container<span class="Delimiter">(</span>h<span class="Delimiter">,</span> r<span class="Delimiter">);</span>
+  assert<span class="Delimiter">(</span><span class="Constant">false</span><span class="Delimiter">);</span>
+<span class="Delimiter">}</span>
+
+<span class="Normal">size_t</span> hash_mu_scalar<span class="Delimiter">(</span><span class="Normal">size_t</span> h<span class="Delimiter">,</span> <span class="Normal">const</span> reagent&amp; r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  <span class="Normal">double</span> input = is_literal<span class="Delimiter">(</span>r<span class="Delimiter">)</span> ? r<span class="Delimiter">.</span>value : get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> r<span class="Delimiter">.</span>value<span class="Delimiter">);</span>
+  <span class="Identifier">return</span> hash_iter<span class="Delimiter">(</span>h<span class="Delimiter">,</span> <span class="Normal">static_cast</span>&lt;<span class="Normal">size_t</span>&gt;<span class="Delimiter">(</span>input<span class="Delimiter">));</span>
+<span class="Delimiter">}</span>
+
+<span class="Normal">size_t</span> hash_mu_address<span class="Delimiter">(</span><span class="Normal">size_t</span> h<span class="Delimiter">,</span> reagent&amp; r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  <span class="Normal">if</span> <span class="Delimiter">(</span>r<span class="Delimiter">.</span>value == <span class="Constant">0</span><span class="Delimiter">)</span> <span class="Identifier">return</span> <span class="Constant">0</span><span class="Delimiter">;</span>
+  r<span class="Delimiter">.</span>value = get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> r<span class="Delimiter">.</span>value<span class="Delimiter">);</span>
+  drop_from_type<span class="Delimiter">(</span>r<span class="Delimiter">,</span> <span class="Constant">&quot;address&quot;</span><span class="Delimiter">);</span>
+  <span class="Normal">if</span> <span class="Delimiter">(</span>r<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>name == <span class="Constant">&quot;shared&quot;</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    ++r<span class="Delimiter">.</span>value<span class="Delimiter">;</span>
+    drop_from_type<span class="Delimiter">(</span>r<span class="Delimiter">,</span> <span class="Constant">&quot;shared&quot;</span><span class="Delimiter">);</span>
+  <span class="Delimiter">}</span>
+  <span class="Identifier">return</span> hash<span class="Delimiter">(</span>h<span class="Delimiter">,</span> r<span class="Delimiter">);</span>
+<span class="Delimiter">}</span>
+
+<span class="Normal">size_t</span> hash_mu_string<span class="Delimiter">(</span><span class="Normal">size_t</span> h<span class="Delimiter">,</span> <span class="Normal">const</span> reagent&amp; r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  string input = read_mu_string<span class="Delimiter">(</span>get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> r<span class="Delimiter">.</span>value<span class="Delimiter">));</span>
+  <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">int</span> i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; SIZE<span class="Delimiter">(</span>input<span class="Delimiter">);</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    h = hash_iter<span class="Delimiter">(</span>h<span class="Delimiter">,</span> <span class="Normal">static_cast</span>&lt;<span class="Normal">size_t</span>&gt;<span class="Delimiter">(</span>input<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">)));</span>
+<span class="CommentedCode">//?     cerr &lt;&lt; i &lt;&lt; &quot;: &quot; &lt;&lt; h &lt;&lt; '\n';</span>
+  <span class="Delimiter">}</span>
+  <span class="Identifier">return</span> h<span class="Delimiter">;</span>
+<span class="Delimiter">}</span>
+
+<span class="Normal">size_t</span> hash_mu_array<span class="Delimiter">(</span><span class="Normal">size_t</span> h<span class="Delimiter">,</span> <span class="Normal">const</span> reagent&amp; r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  <span class="Normal">int</span> size = get_or_insert<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> r<span class="Delimiter">.</span>value<span class="Delimiter">);</span>
+  reagent elem = r<span class="Delimiter">;</span>
+  <span class="Normal">delete</span> elem<span class="Delimiter">.</span>type<span class="Delimiter">;</span>
+  elem<span class="Delimiter">.</span>type = <span class="Normal">new</span> type_tree<span class="Delimiter">(</span>*array_element<span class="Delimiter">(</span>r<span class="Delimiter">.</span>type<span class="Delimiter">));</span>
+  <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">int</span> i=<span class="Constant">0</span><span class="Delimiter">,</span> address = r<span class="Delimiter">.</span>value+<span class="Constant">1</span><span class="Delimiter">;</span> i &lt; size<span class="Delimiter">;</span> ++i<span class="Delimiter">,</span> address += size_of<span class="Delimiter">(</span>elem<span class="Delimiter">))</span> <span class="Delimiter">{</span>
+    reagent tmp = elem<span class="Delimiter">;</span>
+    tmp<span class="Delimiter">.</span>value = address<span class="Delimiter">;</span>
+    h = hash<span class="Delimiter">(</span>h<span class="Delimiter">,</span> tmp<span class="Delimiter">);</span>
+<span class="CommentedCode">//?     cerr &lt;&lt; i &lt;&lt; &quot; (&quot; &lt;&lt; address &lt;&lt; &quot;): &quot; &lt;&lt; h &lt;&lt; '\n';</span>
+  <span class="Delimiter">}</span>
+  <span class="Identifier">return</span> h<span class="Delimiter">;</span>
+<span class="Delimiter">}</span>
+
+<span class="Normal">bool</span> is_mu_container<span class="Delimiter">(</span><span class="Normal">const</span> reagent&amp; r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  <span class="Normal">if</span> <span class="Delimiter">(</span>r<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value == <span class="Constant">0</span><span class="Delimiter">)</span> <span class="Identifier">return</span> <span class="Constant">false</span><span class="Delimiter">;</span>
+  type_info&amp; info = get<span class="Delimiter">(</span>Type<span class="Delimiter">,</span> r<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value<span class="Delimiter">);</span>
+  <span class="Identifier">return</span> info<span class="Delimiter">.</span>kind == CONTAINER<span class="Delimiter">;</span>
+<span class="Delimiter">}</span>
+
+<span class="Normal">size_t</span> hash_mu_container<span class="Delimiter">(</span><span class="Normal">size_t</span> h<span class="Delimiter">,</span> <span class="Normal">const</span> reagent&amp; r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  assert<span class="Delimiter">(</span>r<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value<span class="Delimiter">);</span>
+  type_info&amp; info = get<span class="Delimiter">(</span>Type<span class="Delimiter">,</span> r<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value<span class="Delimiter">);</span>
+  <span class="Normal">int</span> address = r<span class="Delimiter">.</span>value<span class="Delimiter">;</span>
+  <span class="Normal">int</span> offset = <span class="Constant">0</span><span class="Delimiter">;</span>
+  <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">int</span> i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; SIZE<span class="Delimiter">(</span>info<span class="Delimiter">.</span>elements<span class="Delimiter">);</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    reagent element = element_type<span class="Delimiter">(</span>r<span class="Delimiter">,</span> i<span class="Delimiter">);</span>
+    <span class="Normal">if</span> <span class="Delimiter">(</span>has_property<span class="Delimiter">(</span>element<span class="Delimiter">,</span> <span class="Constant">&quot;ignore-for-hash&quot;</span><span class="Delimiter">))</span> <span class="Identifier">continue</span><span class="Delimiter">;</span>
+    element<span class="Delimiter">.</span>set_value<span class="Delimiter">(</span>address+offset<span class="Delimiter">);</span>
+    h = hash<span class="Delimiter">(</span>h<span class="Delimiter">,</span> element<span class="Delimiter">);</span>
+<span class="CommentedCode">//?     cerr &lt;&lt; i &lt;&lt; &quot;: &quot; &lt;&lt; h &lt;&lt; '\n';</span>
+    offset += size_of<span class="Delimiter">(</span>info<span class="Delimiter">.</span>elements<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">).</span>type<span class="Delimiter">);</span>
+  <span class="Delimiter">}</span>
+  <span class="Identifier">return</span> h<span class="Delimiter">;</span>
+<span class="Delimiter">}</span>
+
+<span class="Normal">bool</span> is_mu_exclusive_container<span class="Delimiter">(</span><span class="Normal">const</span> reagent&amp; r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  <span class="Normal">if</span> <span class="Delimiter">(</span>r<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value == <span class="Constant">0</span><span class="Delimiter">)</span> <span class="Identifier">return</span> <span class="Constant">false</span><span class="Delimiter">;</span>
+  type_info&amp; info = get<span class="Delimiter">(</span>Type<span class="Delimiter">,</span> r<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value<span class="Delimiter">);</span>
+  <span class="Identifier">return</span> info<span class="Delimiter">.</span>kind == EXCLUSIVE_CONTAINER<span class="Delimiter">;</span>
+<span class="Delimiter">}</span>
+
+<span class="Normal">size_t</span> hash_mu_exclusive_container<span class="Delimiter">(</span><span class="Normal">size_t</span> h<span class="Delimiter">,</span> <span class="Normal">const</span> reagent&amp; r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  assert<span class="Delimiter">(</span>r<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value<span class="Delimiter">);</span>
+  <span class="Normal">int</span> tag = get<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> r<span class="Delimiter">.</span>value<span class="Delimiter">);</span>
+  reagent variant = variant_type<span class="Delimiter">(</span>r<span class="Delimiter">,</span> tag<span class="Delimiter">);</span>
+  <span class="Comment">// todo: move this error to container definition time</span>
+  <span class="Normal">if</span> <span class="Delimiter">(</span>has_property<span class="Delimiter">(</span>variant<span class="Delimiter">,</span> <span class="Constant">&quot;ignore-for-hash&quot;</span><span class="Delimiter">))</span>
+    raise &lt;&lt; get<span class="Delimiter">(</span>Type<span class="Delimiter">,</span> r<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>value<span class="Delimiter">).</span>name &lt;&lt; <span class="Constant">&quot;: /ignore-for-hash won't work in exclusive containers</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
+  variant<span class="Delimiter">.</span>set_value<span class="Delimiter">(</span>r<span class="Delimiter">.</span>value + <span class="Comment">/*</span><span class="Comment">skip tag</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">);</span>
+  h = hash<span class="Delimiter">(</span>h<span class="Delimiter">,</span> variant<span class="Delimiter">);</span>
+  <span class="Identifier">return</span> h<span class="Delimiter">;</span>
+<span class="Delimiter">}</span>
+
+<span class="Normal">size_t</span> hash_iter<span class="Delimiter">(</span><span class="Normal">size_t</span> h<span class="Delimiter">,</span> <span class="Normal">size_t</span> input<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+  h += input<span class="Delimiter">;</span>
+  h += <span class="Delimiter">(</span>h&lt;&lt;<span class="Constant">10</span><span class="Delimiter">);</span>
+  h ^= <span class="Delimiter">(</span>h&gt;&gt;<span class="Constant">6</span><span class="Delimiter">);</span>
+
+  h += <span class="Delimiter">(</span>h&lt;&lt;<span class="Constant">3</span><span class="Delimiter">);</span>
+  h ^= <span class="Delimiter">(</span>h&gt;&gt;<span class="Constant">11</span><span class="Delimiter">);</span>
+  h += <span class="Delimiter">(</span>h&lt;&lt;<span class="Constant">15</span><span class="Delimiter">);</span>
+  <span class="Identifier">return</span> h<span class="Delimiter">;</span>
+<span class="Delimiter">}</span>
+
+<span class="Delimiter">:(scenario hash_container_checks_all_elements)</span>
+container foo [
+  <span class="Normal">x</span>:number
+  <span class="Normal">y</span>:character
+]
+def main [
+  <span class="Constant">1</span>:foo<span class="Special"> &lt;- </span>merge <span class="Constant">34</span><span class="Delimiter">,</span> <span class="Constant">97</span>/a
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">1</span>:foo
+  <span class="Identifier">return</span>-unless <span class="Constant">3</span>:number
+  <span class="Constant">4</span>:foo<span class="Special"> &lt;- </span>merge <span class="Constant">34</span><span class="Delimiter">,</span> <span class="Constant">98</span>/a
+  <span class="Constant">6</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">4</span>:foo
+  <span class="Identifier">return</span>-unless <span class="Constant">6</span>:number
+  <span class="Constant">7</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number<span class="Delimiter">,</span> <span class="Constant">6</span>:number
+]
+<span class="Comment"># hash on containers includes all elements</span>
+<span class="traceContains">+mem: storing 0 in location 7</span>
+
+<span class="Delimiter">:(scenario hash_exclusive_container_checks_all_elements)</span>
+exclusive-container foo [
+  <span class="Normal">x</span>:bar
+  <span class="Normal">y</span>:number
+]
+container bar [
+  <span class="Normal">a</span>:number
+  <span class="Normal">b</span>:number
+]
+def main [
+  <span class="Constant">1</span>:foo<span class="Special"> &lt;- </span>merge <span class="Constant">0</span>/x<span class="Delimiter">,</span> <span class="Constant">34</span><span class="Delimiter">,</span> <span class="Constant">35</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">1</span>:foo
+  <span class="Identifier">return</span>-unless <span class="Constant">4</span>:number
+  <span class="Constant">5</span>:foo<span class="Special"> &lt;- </span>merge <span class="Constant">0</span>/x<span class="Delimiter">,</span> <span class="Constant">34</span><span class="Delimiter">,</span> <span class="Constant">36</span>
+  <span class="Constant">8</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">5</span>:foo
+  <span class="Identifier">return</span>-unless <span class="Constant">8</span>:number
+  <span class="Constant">9</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">4</span>:number<span class="Delimiter">,</span> <span class="Constant">8</span>:number
+]
+<span class="Comment"># hash on containers includes all elements</span>
+<span class="traceContains">+mem: storing 0 in location 9</span>
+
+<span class="Delimiter">:(scenario hash_can_ignore_container_elements)</span>
+container foo [
+  <span class="Normal">x</span>:number
+  <span class="Normal">y</span>:character/ignore-<span class="Normal">for</span>-hash
+]
+def main [
+  <span class="Constant">1</span>:foo<span class="Special"> &lt;- </span>merge <span class="Constant">34</span><span class="Delimiter">,</span> <span class="Constant">97</span>/a
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">1</span>:foo
+  <span class="Identifier">return</span>-unless <span class="Constant">3</span>:number
+  <span class="Constant">4</span>:foo<span class="Special"> &lt;- </span>merge <span class="Constant">34</span><span class="Delimiter">,</span> <span class="Constant">98</span>/a
+  <span class="Constant">6</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">4</span>:foo
+  <span class="Identifier">return</span>-unless <span class="Constant">6</span>:number
+  <span class="Constant">7</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number<span class="Delimiter">,</span> <span class="Constant">6</span>:number
+]
+<span class="Comment"># hashes match even though y is different</span>
+<span class="traceContains">+mem: storing 1 in location 7</span>
+
+<span class="Comment">//: These properties aren't necessary for hash, they just test that the</span>
+<span class="Comment">//: current implementation works like we think it does.</span>
+
+<span class="Delimiter">:(scenario hash_of_zero_address)</span>
+def main [
+  <span class="Constant">1</span>:address:number<span class="Special"> &lt;- </span>copy <span class="Constant">0</span>
+  <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">1</span>:address:number
+]
+<span class="traceContains">+mem: storing 0 in location 2</span>
+
+<span class="Comment">//: This is probably too aggressive, but we need some way to avoid depending</span>
+<span class="Comment">//: on the precise bit pattern of a floating-point number.</span>
+<span class="Delimiter">:(scenario hash_of_numbers_ignores_fractional_part)</span>
+def main [
+  <span class="Constant">1</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">1.5</span>
+  <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">1</span>
+  <span class="Constant">3</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">1</span>:number<span class="Delimiter">,</span> <span class="Constant">2</span>:number
+]
+<span class="traceContains">+mem: storing 1 in location 3</span>
+
+<span class="Delimiter">:(scenario hash_of_array_same_as_string)</span>
+def main [
+  <span class="Constant">10</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">3</span>
+  <span class="Constant">11</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">97</span>
+  <span class="Constant">12</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">98</span>
+  <span class="Constant">13</span>:number<span class="Special"> &lt;- </span>copy <span class="Constant">99</span>
+  <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">10</span>:array:number/unsafe
+  <span class="Identifier">return</span>-unless <span class="Constant">2</span>:number
+  <span class="Constant">3</span>:address:shared:array:character<span class="Special"> &lt;- </span><span class="Normal">new</span> [abc]
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">3</span>:address:shared:array:character
+  <span class="Identifier">return</span>-unless <span class="Constant">4</span>:number
+  <span class="Constant">5</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">2</span>:number<span class="Delimiter">,</span> <span class="Constant">4</span>:number
+]
+<span class="traceContains">+mem: storing 1 in location 5</span>
+
+<span class="Delimiter">:(scenario hash_ignores_address_value)</span>
+def main [
+  <span class="Constant">1</span>:address:shared:number<span class="Special"> &lt;- </span><span class="Normal">new</span> number:type
+  *<span class="Constant">1</span>:address:shared:number<span class="Special"> &lt;- </span>copy <span class="Constant">34</span>
+  <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">1</span>:address:shared:number
+  <span class="Constant">3</span>:address:shared:number<span class="Special"> &lt;- </span><span class="Normal">new</span> number:type
+  *<span class="Constant">3</span>:address:shared:number<span class="Special"> &lt;- </span>copy <span class="Constant">34</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">3</span>:address:shared:number
+  <span class="Constant">5</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">2</span>:number<span class="Delimiter">,</span> <span class="Constant">4</span>:number
+]
+<span class="Comment"># different addresses hash to the same result as long as the values the point to do so</span>
+<span class="traceContains">+mem: storing 1 in location 5</span>
+
+<span class="Delimiter">:(scenario hash_ignores_address_refcount)</span>
+def main [
+  <span class="Constant">1</span>:address:shared:number<span class="Special"> &lt;- </span><span class="Normal">new</span> number:type
+  *<span class="Constant">1</span>:address:shared:number<span class="Special"> &lt;- </span>copy <span class="Constant">34</span>
+  <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">1</span>:address:shared:number
+  <span class="Identifier">return</span>-unless <span class="Constant">2</span>:number
+  <span class="Comment"># increment refcount</span>
+  <span class="Constant">3</span>:address:shared:number<span class="Special"> &lt;- </span>copy <span class="Constant">1</span>:address:shared:number
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">3</span>:address:shared:number
+  <span class="Identifier">return</span>-unless <span class="Constant">4</span>:number
+  <span class="Constant">5</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">2</span>:number<span class="Delimiter">,</span> <span class="Constant">4</span>:number
+]
+<span class="Comment"># hash doesn't change when refcount changes</span>
+<span class="traceContains">+mem: storing 1 in location 5</span>
+
+<span class="Delimiter">:(scenario hash_container_depends_only_on_elements)</span>
+container foo [
+  <span class="Normal">x</span>:number
+  <span class="Normal">y</span>:character
+]
+container bar [
+  <span class="Normal">x</span>:number
+  <span class="Normal">y</span>:character
+]
+def main [
+  <span class="Constant">1</span>:foo<span class="Special"> &lt;- </span>merge <span class="Constant">34</span><span class="Delimiter">,</span> <span class="Constant">97</span>/a
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">1</span>:foo
+  <span class="Identifier">return</span>-unless <span class="Constant">3</span>:number
+  <span class="Constant">4</span>:bar<span class="Special"> &lt;- </span>merge <span class="Constant">34</span><span class="Delimiter">,</span> <span class="Constant">97</span>/a
+  <span class="Constant">6</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">4</span>:bar
+  <span class="Identifier">return</span>-unless <span class="Constant">6</span>:number
+  <span class="Constant">7</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">3</span>:number<span class="Delimiter">,</span> <span class="Constant">6</span>:number
+]
+<span class="Comment"># containers with identical elements return identical hashes</span>
+<span class="traceContains">+mem: storing 1 in location 7</span>
+
+<span class="Delimiter">:(scenario hash_container_depends_only_on_elements_2)</span>
+container foo [
+  <span class="Normal">x</span>:number
+  <span class="Normal">y</span>:character
+  <span class="Normal">z</span>:address:shared:number
+]
+def main [
+  <span class="Constant">1</span>:address:shared:number<span class="Special"> &lt;- </span><span class="Normal">new</span> number:type
+  *<span class="Constant">1</span>:address:shared:number<span class="Special"> &lt;- </span>copy <span class="Constant">34</span>
+  <span class="Constant">2</span>:foo<span class="Special"> &lt;- </span>merge <span class="Constant">34</span><span class="Delimiter">,</span> <span class="Constant">97</span>/a<span class="Delimiter">,</span> <span class="Constant">1</span>:address:shared:number
+  <span class="Constant">5</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">2</span>:foo
+  <span class="Identifier">return</span>-unless <span class="Constant">5</span>:number
+  <span class="Constant">6</span>:address:shared:number<span class="Special"> &lt;- </span><span class="Normal">new</span> number:type
+  *<span class="Constant">6</span>:address:shared:number<span class="Special"> &lt;- </span>copy <span class="Constant">34</span>
+  <span class="Constant">7</span>:foo<span class="Special"> &lt;- </span>merge <span class="Constant">34</span><span class="Delimiter">,</span> <span class="Constant">97</span>/a<span class="Delimiter">,</span> <span class="Constant">6</span>:address:shared:number
+  <span class="Constant">10</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">7</span>:foo
+  <span class="Identifier">return</span>-unless <span class="Constant">10</span>:number
+  <span class="Constant">11</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">5</span>:number<span class="Delimiter">,</span> <span class="Constant">10</span>:number
+]
+<span class="Comment"># containers with identical 'leaf' elements return identical hashes</span>
+<span class="traceContains">+mem: storing 1 in location 11</span>
+
+<span class="Delimiter">:(scenario hash_container_depends_only_on_elements_3)</span>
+container foo [
+  <span class="Normal">x</span>:number
+  <span class="Normal">y</span>:character
+  <span class="Normal">z</span>:bar
+]
+container bar [
+  <span class="Normal">x</span>:number
+  <span class="Normal">y</span>:number
+]
+def main [
+  <span class="Constant">1</span>:foo<span class="Special"> &lt;- </span>merge <span class="Constant">34</span><span class="Delimiter">,</span> <span class="Constant">97</span>/a<span class="Delimiter">,</span> <span class="Constant">47</span><span class="Delimiter">,</span> <span class="Constant">48</span>
+  <span class="Constant">6</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">1</span>:foo
+  <span class="Identifier">return</span>-unless <span class="Constant">6</span>:number
+  <span class="Constant">7</span>:foo<span class="Special"> &lt;- </span>merge <span class="Constant">34</span><span class="Delimiter">,</span> <span class="Constant">97</span>/a<span class="Delimiter">,</span> <span class="Constant">47</span><span class="Delimiter">,</span> <span class="Constant">48</span>
+  <span class="Constant">12</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">7</span>:foo
+  <span class="Identifier">return</span>-unless <span class="Constant">12</span>:number
+  <span class="Constant">13</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">6</span>:number<span class="Delimiter">,</span> <span class="Constant">12</span>:number
+]
+<span class="Comment"># containers with identical 'leaf' elements return identical hashes</span>
+<span class="traceContains">+mem: storing 1 in location 13</span>
+
+<span class="Delimiter">:(scenario hash_exclusive_container_ignores_tag)</span>
+exclusive-container foo [
+  <span class="Normal">x</span>:bar
+  <span class="Normal">y</span>:number
+]
+container bar [
+  <span class="Normal">a</span>:number
+  <span class="Normal">b</span>:number
+]
+def main [
+  <span class="Constant">1</span>:foo<span class="Special"> &lt;- </span>merge <span class="Constant">0</span>/x<span class="Delimiter">,</span> <span class="Constant">34</span><span class="Delimiter">,</span> <span class="Constant">35</span>
+  <span class="Constant">4</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">1</span>:foo
+  <span class="Identifier">return</span>-unless <span class="Constant">4</span>:number
+  <span class="Constant">5</span>:bar<span class="Special"> &lt;- </span>merge <span class="Constant">34</span><span class="Delimiter">,</span> <span class="Constant">35</span>
+  <span class="Constant">7</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">5</span>:bar
+  <span class="Identifier">return</span>-unless <span class="Constant">7</span>:number
+  <span class="Constant">8</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">4</span>:number<span class="Delimiter">,</span> <span class="Constant">7</span>:number
+]
+<span class="Comment"># hash on containers includes all elements</span>
+<span class="traceContains">+mem: storing 1 in location 8</span>
+
+<span class="Comment">//: An older version that supported only strings.</span>
+<span class="Comment">//: Hash functions are subtle and easy to get wrong, so we keep the old</span>
+<span class="Comment">//: version around and check that the new one is consistent with it.</span>
+
+<span class="Delimiter">:(scenario hash_matches_old_version)</span>
+def main [
+  <span class="Constant">1</span>:address:shared:array:character<span class="Special"> &lt;- </span><span class="Normal">new</span> [abc]
+  <span class="Constant">2</span>:number<span class="Special"> &lt;- </span>hash <span class="Constant">1</span>:address:shared:array:character
+  <span class="Constant">3</span>:number<span class="Special"> &lt;- </span>hash_old <span class="Constant">1</span>:address:shared:array:character
+  <span class="Constant">4</span>:boolean<span class="Special"> &lt;- </span>equal <span class="Constant">2</span>:number<span class="Delimiter">,</span> <span class="Constant">3</span>:number
+]
+<span class="traceContains">+mem: storing 1 in location 4</span>
+
+<span class="Delimiter">:(before &quot;End Primitive Recipe Declarations&quot;)</span>
+HASH_OLD<span class="Delimiter">,</span>
+<span class="Delimiter">:(before &quot;End Primitive Recipe Numbers&quot;)</span>
+put<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;hash_old&quot;</span><span class="Delimiter">,</span> HASH_OLD<span class="Delimiter">);</span>
+<span class="Delimiter">:(before &quot;End Primitive Recipe Checks&quot;)</span>
+<span class="Normal">case</span> HASH_OLD: <span class="Delimiter">{</span>
+  <span class="Normal">if</span> <span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">)</span> != <span class="Constant">1</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    raise &lt;&lt; maybe<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;'hash_old' takes exactly one ingredient rather than '&quot;</span> &lt;&lt; to_original_string<span class="Delimiter">(</span>inst<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
+    <span class="Identifier">break</span><span class="Delimiter">;</span>
+  <span class="Delimiter">}</span>
+  <span class="Normal">if</span> <span class="Delimiter">(</span>!is_mu_string<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">)))</span> <span class="Delimiter">{</span>
+    raise &lt;&lt; maybe<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;'hash_old' currently only supports strings (address:shared:array:character), but got &quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>original_string &lt;&lt; <span class="cSpecial">'\n'</span> &lt;&lt; end<span class="Delimiter">();</span>
+    <span class="Identifier">break</span><span class="Delimiter">;</span>
+  <span class="Delimiter">}</span>
+  <span class="Identifier">break</span><span class="Delimiter">;</span>
+<span class="Delimiter">}</span>
+<span class="Delimiter">:(before &quot;End Primitive Recipe Implementations&quot;)</span>
+<span class="Normal">case</span> HASH_OLD: <span class="Delimiter">{</span>
+  string input = read_mu_string<span class="Delimiter">(</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">));</span>
+  <span class="Normal">size_t</span> h = <span class="Constant">0</span> <span class="Delimiter">;</span>
+
+  <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">int</span> i = <span class="Constant">0</span><span class="Delimiter">;</span> i &lt; SIZE<span class="Delimiter">(</span>input<span class="Delimiter">);</span> ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
+    h += <span class="Normal">static_cast</span>&lt;<span class="Normal">size_t</span>&gt;<span class="Delimiter">(</span>input<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">));</span>
+    h += <span class="Delimiter">(</span>h&lt;&lt;<span class="Constant">10</span><span class="Delimiter">);</span>
+    h ^= <span class="Delimiter">(</span>h&gt;&gt;<span class="Constant">6</span><span class="Delimiter">);</span>
+
+    h += <span class="Delimiter">(</span>h&lt;&lt;<span class="Constant">3</span><span class="Delimiter">);</span>
+    h ^= <span class="Delimiter">(</span>h&gt;&gt;<span class="Constant">11</span><span class="Delimiter">);</span>
+    h += <span class="Delimiter">(</span>h&lt;&lt;<span class="Constant">15</span><span class="Delimiter">);</span>
+  <span class="Delimiter">}</span>
+
+  products<span class="Delimiter">.</span>resize<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">);</span>
+  products<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>push_back<span class="Delimiter">(</span>h<span class="Delimiter">);</span>
+  <span class="Identifier">break</span><span class="Delimiter">;</span>
+<span class="Delimiter">}</span>
+</pre>
+</body>
+</html>
+<!-- vim: set foldmethod=manual : -->
author	Kartik K. Agaram <vc@akkartik.com>	2016-03-26 23:59:59 -0700
committer	Kartik K. Agaram <vc@akkartik.com>	2016-03-27 17:43:41 -0700
commit	a654e4ecace2d506d1b10f1dde2c287ebe84ef37 (patch)
tree	1e34a3ad99a56e32bdf9ee03ecfe7d339e7942ae /html/078hash.cc.html
parent	859f35fbe2f6a78157b875e12eb7dc8cd95c1152 (diff)
download	mu-a654e4ecace2d506d1b10f1dde2c287ebe84ef37.tar.gz