HTML build

Author: rougier

Diff for: book.html

@@ -28,7 +28,7 @@ <h2 class="subtitle" id="copyright-c-2017-nicolas-p-rougier-nicolas-rougier-inri
 <img alt="data/nc.large.png" src="data/nc.large.png" style="width: 40px;" />
 <div class="line-block">
 <div class="line"><br /></div>
-<div class="line">Latest version - August 2017</div>
+<div class="line">Latest version - October 2017</div>
 <div class="line">DOI: <a class="reference external" href="http://doi.org/10.5281/zenodo.225783">10.5281/zenodo.225783</a></div>
 </div>
 </div>
@@ -389,7 +389,7 @@ <h2><a class="toc-backref" href="#id3">Readability vs speed</a></h2>
 and you don't need to read this book).</p>
 <pre class="code python literal-block">
 <span class="keyword">def</span> <span class="name function">function_1</span><span class="punctuation">(</span><span class="name">seq</span><span class="punctuation">,</span> <span class="name">sub</span><span class="punctuation">):</span>
-    <span class="keyword">return</span> <span class="punctuation">[</span><span class="name">i</span> <span class="keyword">for</span> <span class="name">i</span> <span class="operator word">in</span> <span class="name builtin">range</span><span class="punctuation">(</span><span class="name builtin">len</span><span class="punctuation">(</span><span class="name">seq</span><span class="punctuation">)</span> <span class="operator">-</span> <span class="name builtin">len</span><span class="punctuation">(</span><span class="name">sub</span><span class="punctuation">))</span> <span class="keyword">if</span> <span class="name">seq</span><span class="punctuation">[</span><span class="name">i</span><span class="punctuation">:</span><span class="name">i</span><span class="operator">+</span><span class="name builtin">len</span><span class="punctuation">(</span><span class="name">sub</span><span class="punctuation">)]</span> <span class="operator">==</span> <span class="name">sub</span><span class="punctuation">]</span>
+    <span class="keyword">return</span> <span class="punctuation">[</span><span class="name">i</span> <span class="keyword">for</span> <span class="name">i</span> <span class="operator word">in</span> <span class="name builtin">range</span><span class="punctuation">(</span><span class="name builtin">len</span><span class="punctuation">(</span><span class="name">seq</span><span class="punctuation">)</span> <span class="operator">-</span> <span class="name builtin">len</span><span class="punctuation">(</span><span class="name">sub</span><span class="punctuation">)</span> <span class="operator">+</span><span class="literal number integer">1</span><span class="punctuation">)</span> <span class="keyword">if</span> <span class="name">seq</span><span class="punctuation">[</span><span class="name">i</span><span class="punctuation">:</span><span class="name">i</span><span class="operator">+</span><span class="name builtin">len</span><span class="punctuation">(</span><span class="name">sub</span><span class="punctuation">)]</span> <span class="operator">==</span> <span class="name">sub</span><span class="punctuation">]</span>
 
 <span class="keyword">def</span> <span class="name function">function_2</span><span class="punctuation">(</span><span class="name">seq</span><span class="punctuation">,</span> <span class="name">sub</span><span class="punctuation">):</span>
     <span class="name">target</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">dot</span><span class="punctuation">(</span><span class="name">sub</span><span class="punctuation">,</span> <span class="name">sub</span><span class="punctuation">)</span>
@@ -504,20 +504,21 @@ <h2><a class="toc-backref" href="#id4">Memory layout</a></h2>
 an index tuple) and more precisely, how to compute the start and end offsets:</p>
 <pre class="code python literal-block">
 <span class="name">offset_start</span> <span class="operator">=</span> <span class="literal number integer">0</span>
-<span class="keyword">for</span> <span class="name">i</span> <span class="operator word">in</span> <span class="name builtin">range</span><span class="punctuation">(</span><span class="name">ndim</span><span class="punctuation">):</span>
-    <span class="name">offset_start</span> <span class="operator">+=</span> <span class="name">strides</span><span class="punctuation">[</span><span class="name">i</span><span class="punctuation">]</span><span class="operator">*</span><span class="name">index</span><span class="punctuation">[</span><span class="name">i</span><span class="punctuation">]</span>
+<span class="keyword">for</span> <span class="name">i</span> <span class="operator word">in</span> <span class="name builtin">range</span><span class="punctuation">(</span><span class="name">Z</span><span class="operator">.</span><span class="name">ndim</span><span class="punctuation">):</span>
+    <span class="name">offset_start</span> <span class="operator">+=</span> <span class="name">Z</span><span class="operator">.</span><span class="name">strides</span><span class="punctuation">[</span><span class="name">i</span><span class="punctuation">]</span> <span class="operator">*</span> <span class="name">index</span><span class="punctuation">[</span><span class="name">i</span><span class="punctuation">]</span>
 <span class="name">offset_end</span> <span class="operator">=</span> <span class="name">offset_start</span> <span class="operator">+</span> <span class="name">Z</span><span class="operator">.</span><span class="name">itemsize</span>
 </pre>
 <p>Let's see if this is correct using the <a class="reference external" href="https://docs.scipy.org/doc/numpy/reference/generated/numpy.ndarray.tobytes.html">tobytes</a>
 conversion method:</p>
 <pre class="code python literal-block">
-<span class="operator">&gt;&gt;&gt;</span> <span class="name">Z</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">arange</span><span class="punctuation">(</span><span class="literal number integer">9</span><span class="punctuation">)</span><span class="operator">.</span><span class="name">reshape</span><span class="punctuation">(</span><span class="literal number integer">3</span><span class="punctuation">,</span><span class="literal number integer">3</span><span class="punctuation">)</span><span class="operator">.</span><span class="name">astype</span><span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">int16</span><span class="punctuation">)</span>
-<span class="operator">&gt;&gt;&gt;</span> <span class="name">index</span> <span class="operator">=</span> <span class="literal number integer">1</span><span class="punctuation">,</span><span class="literal number integer">1</span>
+<span class="operator">&gt;&gt;&gt;</span> <span class="name">Z</span> <span class="operator">=</span> <span class="name">np</span><span class="operator">.</span><span class="name">arange</span><span class="punctuation">(</span><span class="literal number integer">9</span><span class="punctuation">)</span><span class="operator">.</span><span class="name">reshape</span><span class="punctuation">(</span><span class="literal number integer">3</span><span class="punctuation">,</span> <span class="literal number integer">3</span><span class="punctuation">)</span><span class="operator">.</span><span class="name">astype</span><span class="punctuation">(</span><span class="name">np</span><span class="operator">.</span><span class="name">int16</span><span class="punctuation">)</span>
+<span class="operator">&gt;&gt;&gt;</span> <span class="name">index</span> <span class="operator">=</span> <span class="literal number integer">1</span><span class="punctuation">,</span> <span class="literal number integer">1</span>
 <span class="operator">&gt;&gt;&gt;</span> <span class="keyword">print</span><span class="punctuation">(</span><span class="name">Z</span><span class="punctuation">[</span><span class="name">index</span><span class="punctuation">]</span><span class="operator">.</span><span class="name">tobytes</span><span class="punctuation">())</span>
 <span class="literal string affix">b</span><span class="literal string single">'</span><span class="literal string escape">\x04\x00</span><span class="literal string single">'</span>
-<span class="operator">&gt;&gt;&gt;</span> <span class="name">offset</span> <span class="operator">=</span> <span class="literal number integer">0</span>
+<span class="operator">&gt;&gt;&gt;</span> <span class="name">offset_start</span> <span class="operator">=</span> <span class="literal number integer">0</span>
 <span class="operator">&gt;&gt;&gt;</span> <span class="keyword">for</span> <span class="name">i</span> <span class="operator word">in</span> <span class="name builtin">range</span><span class="punctuation">(</span><span class="name">Z</span><span class="operator">.</span><span class="name">ndim</span><span class="punctuation">):</span>
-<span class="operator">...</span>     <span class="name">offset</span> <span class="operator">+</span> <span class="operator">=</span> <span class="name">Z</span><span class="operator">.</span><span class="name">strides</span><span class="punctuation">[</span><span class="name">i</span><span class="punctuation">]</span><span class="operator">*</span><span class="name">index</span><span class="punctuation">[</span><span class="name">i</span><span class="punctuation">]</span>
+<span class="operator">...</span>     <span class="name">offset_start</span> <span class="operator">+=</span> <span class="name">Z</span><span class="operator">.</span><span class="name">strides</span><span class="punctuation">[</span><span class="name">i</span><span class="punctuation">]</span> <span class="operator">*</span> <span class="name">index</span><span class="punctuation">[</span><span class="name">i</span><span class="punctuation">]</span>
+<span class="operator">&gt;&gt;&gt;</span> <span class="name">offset_end</span> <span class="operator">=</span> <span class="name">offset_start</span> <span class="operator">+</span> <span class="name">Z</span><span class="operator">.</span><span class="name">itemsize</span>
 <span class="operator">&gt;&gt;&gt;</span> <span class="keyword">print</span><span class="punctuation">(</span><span class="name">Z</span><span class="operator">.</span><span class="name">tobytes</span><span class="punctuation">()[</span><span class="name">offset_start</span><span class="punctuation">:</span><span class="name">offset_end</span><span class="punctuation">]</span>
 <span class="literal string affix">b</span><span class="literal string single">'</span><span class="literal string escape">\x04\x00</span><span class="literal string single">'</span>
 </pre>