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<!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no">
<title>reveal.js</title>
<link rel="stylesheet" href="css/reveal.css">
<link rel="stylesheet" href="css/theme/black.css">
<link rel="stylesheet" href="genericons.css">
<link rel="stylesheet" href="lib/css/zenburn.css">
<!-- Printing and PDF exports -->
<script>
var link = document.createElement( 'link' );
link.rel = 'stylesheet';
link.type = 'text/css';
link.href = window.location.search.match( /print-pdf/gi ) ? 'css/print/pdf.css' : 'css/print/paper.css';
document.getElementsByTagName( 'head' )[0].appendChild( link );
</script>
<style>
.reveal section img {
border: none;
background-color: initial;
margin: 10px;
}
.reveal .normal-paragraph {
text-align: left;
margin: 0 auto 0 auto;
width: 60%;
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.reveal .genericon {
font-family: "genericons";
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.reveal .bio-card {
background: #333;
border-radius: 2px;
display: inline-block;
width: 260px;
margin: 1rem;
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font-size: 20px;
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display: block;
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border-top-left-radius: 2px;
border-top-right-radius: 2px;
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text-decoration: none;
}
.reveal .bio-photo {
width: 200px;
margin: 0 40px 40px -40px;
float: left;
}
</style>
</head>
<body>
<div id="common" style="z-index: 2;">
<div class="header-left">
<img alt="QuantStack" src="quantstack-white.svg" width="30%"/>
</div>
<div class="footer-left">
<div style="color: white; font-family: Source Sans Pro, Helvetica, sans-serif;">
<img alt="Twitter" src="twitter-white.svg" height="20px"/>
<img alt="GitHub" src="github-white.svg" height="20px"/>
<p style="display: inline; vertical-align: top; margin-left: 4px; font-size: 20px;">@SylvainCorlay @JohanMabille @QuantStack</p>
</div>
</div>
</div>
<div class="reveal">
<div class="slides">
<section>
<img alt="xtensor" src="xtensor.svg" width="80%"/>
<p>Data structures for data science</p>
</section>
<section>
<img alt="QuantStack" src="quantstack-white.svg" width="55%">
<div class="team-section-content">
<div style="display: inline-block; width: 45%; margin: 30px; vertical-align: top;">
<img class="card-photo" alt="Avatar picture" src="sylvain.png">
<p class="card-header">Sylvain Corlay</p>
<div style="font-size: 20px; text-align: justify; margin: 30px;">
<ul>
<li>Scientific software developer, Quant researcher, formerly quant at Bloomberg, and adjunct at Columbia and NYU</li>
<li>Founded QuantStack in 2016</li>
<li>Jupyter core developer (widgets, bqplot, pythreejs)</li>
</ul>
</div>
<div class="card-info" style="display: inline;">
<a href="https://github.com/SylvainCorlay" target="_blank">
<span class="genericon genericon-github"></span>
<em>@SylvainCorlay</em>
</a>
</div>
<div class="card-info" style="display: inline;">
<a href="https://twitter.com/SylvainCorlay" target="_blank">
<span class="genericon genericon-twitter"></span>
<em>@SylvainCorlay</em>
</a>
</div>
</div>
<div style="display: inline-block; width: 45%; margin: 30px; vertical-align: top;">
<img class="card-photo" alt="Avatar picture" src="johan.jpg">
<p class="card-header">Johan Mabille</p>
<div style="font-size: 20px; text-align: justify; margin: 30px;">
<ul>
<li>Scientific software developer, Quant developer, formerly quant developer at HSBC</li>
<li>Joined QuantStack in 2016</li>
<li>Co-author of xtensor, xsimd, xeus</li>
</ul>
</div>
<div class="card-info" style="display: inline;">
<a href="https://github.com/JohanMabille" target="_blank">
<span class="genericon genericon-github"></span>
<em>@JohanMabille</em>
</a>
</div>
<div class="card-info" style="display: inline;">
<a href="https://twitter.com/JohanMabille" target="_blank">
<span class="genericon genericon-twitter"></span>
<em>@JohanMabille</em>
</a>
</div>
</div>
</div>
</section>
<section>
<h2>State of the art</h2>
<p>The three main languages of data science</p>
<img alt="Julia" src="JuliaLogo.svg" width="10%"/>
<img alt="Python" src="PythonLogo.svg" width="8%"/>
<img alt="R" src="RLogo.svg" width="10%"/>
<p>all have concepts of</p>
<ul>
<li>N-D arrays</li>
<li>Data frames</li>
</ul>
<p>but with slightly different semantics and incompatible in-memory representation</p>
</section>
<section>
<h2>A new standard for dataframes and tensors?</h2>
<img alt="xkcd-standards" src="xkcd-standards.png" width="60%"/>
</section>
<section>
<h2>2015 Berkeley Workshop</h2>
<p>Data Structures for Data Science</p>
<div class=".normal-paragraph">
<img alt="Workshop" src="workshop-berkeley.jpg" width="30%" style="float: right;"/>
<p style="text-align: left; margin: 44px;">
On November 9, 2015, key developers from the R and Python ecosystems gathered in Berkeley for a workshop to explore
data structures across programming languages and Packages.
</p>
</div>
</section>
<section>
<h2>Their conclusions</h2>
<div style="width: 70%; margin: auto;">
<ul>
<li>Enforce common formats and protocols to communicate and store these data structures.</li>
<li>Support for these protocols accross all three languages.</li>
<li>Converge on common native C++ implementations of these data structures with bindings for multiple scripting languages.</li>
</ul>
</div>
</section>
<section>
<h2>One Tensor to Rule Them All</h2>
<img alt="Ring" src="ring.png" width="30%"/>
<p class="fragment">What would it look like?</p>
</section>
<section>
<h2>One Tensor to Rule Them All: The Requirements</h2>
<div style="text-align: left; margin: auto; width: 70%;">
<ul>
<li>Be as cool as NumPy</li>
<li>Enable use of data structures from existing tensor libraries transparently</li>
<li>Enable transparent use of large tensors backed by database calls or the file system.</li>
</ul>
<p>The One Tensor to Rule them All cannot be just one container implementation.</p>
<p>Instead, it has to be a flexible expression system in which any data structure can be plugged, offering the most expressive and flexible API to the users.</p>
</div>
</section>
<section>
<img alt="xtensor" src="xtensor.svg" width="80%"/>
<p>The Lazy Tensor Algebra Expression System</p>
</section>
<section>
<h2>What is xtensor?</h2>
<ul>
<li class="fragment">
<p>A C++ template library for multi-dimensional array manipulation</p>
<img alt="xtensor" src="xtensor.svg" width="12%"/>
<ul>
<li>
<p>Followings the idioms of the C++ STL</p>
<p>(iterator pairs, clear value semantics)</p>
</li>
<li>But also an API similar to that of numpy</li>
</ul>
</li>
<li class="fragment">
<p>Python bindings to enable xtensor APIs on numpy arrays.</p>
<img alt="xtensor-python" src="xtensor-python.svg" width="20%"/>
</li>
<li class="fragment">
<p>A cookiecutter project for authoring of Python extensions.</p>
<img alt="xtensor-cookiecutter" src="xtensor-cookiecutter.png" width="20%"/>
</li>
<li class="fragment">All open-source (BSD License).</li>
</ul>
</section>
<section>
<h2>Resources</h2>
<ul>
<li>Sources: <em>https://github.com/QuantStack/xtensor/</em></li>
<li>Documentation: <em>http://xtensor.readthedocs.io</em></li>
<li>Python bindings: <em>https://github.com/QuantStack/xtensor-python/</em></li>
<li>Documentation for bindings: <em>http://xtensor-python.readthedocs.io</em></li>
</ul>
</section>
<section>
<style>
div.splitting {
background-color: rgb(20, 98, 135);
width: 50%;
height: 800%;
position: absolute;
top: -200%;
left: 0;
z-index: -1;
}
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width: 45%;
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</style>
<section>
<div class="splitting"></div>
<div>
<p style="text-align: center; vertical-align: top;">Ever heard of numpy ?</p>
</div>
<div>
<div class="left-panel">
<p style="text-align: center;"><b>Python 3 - numpy</b></p>
</div>
<div class="right-panel">
<p style="text-align: center;"><b>C++ 14 - xtensor</b></p>
</div>
</div>
<div class="fragment">
<div class="left-panel">
<pre class="panel"><code class="python panel" data-trim>
np.array([[3, 4], [5, 6]])
arr.reshape([3, 4])
</code></pre>
</div>
<div class="right-panel">
<pre class="panel"><code class="cpp panel" data-trim>
xt::xarray<double>({{3, 4}, {5, 6}})
xt::xtensor<double, 2>({{3, 4}, {5, 6}})
arr.reshape({3, 4});
</code></pre>
</div>
</div>
<div class="fragment">
<div class="left-panel">
<pre class="panel"><code class="python panel" data-trim>
np.linspace(1.0, 10.0, 100)
np.logspace(1.0, 10.0, 100)
np.arange(3, 7)
np.eye(4)
np.zeros([3, 4])
np.ones([3, 4])
</code></pre>
</div>
<div class="right-panel">
<pre class="panel"><code class="cpp panel" data-trim>
xt::linspace<double>(1.0, 10.0, 100)
xt::logspace<double>(1.0, 10.0, 100)
xt::arange(3, 7)
xt::eye(4)
xt::zeros<double>({3, 4})
xt::ones<double>({3, 4})
</code></pre>
</div>
</div>
</section>
<section>
<div class="splitting"></div>
<div>
<div class="left-panel">
<p style="text-align: center;"><b>Python 3 - numpy</b></p>
</div>
<div class="right-panel">
<p style="text-align: center;"><b>C++ 14 - xtensor</b></p>
</div>
</div>
<div class="fragment">
<div class="left-panel">
<pre class="panel"><code class="python panel" data-trim>
a[:, np.newaxis]
a[:5, 1:]
a[5:1:-1, :]
np.broadcast(a, [4, 5, 7])
np.vectorize(f)
a[a > 5]
a[[0, 1], [0, 0]]
</code></pre>
</div>
<div class="right-panel">
<pre class="panel"><code class="cpp panel" data-trim>
xt::view(a, xt::all(), xt::newaxis())
xt::view(a, xt::range(_, 5), xt::range(1, _))
xt::view(a, xt::range(5, 1, -1), xt::all())
xt::broadcast(a, {4, 5, 7})
xt::vectorize(f)
xt::filter(a, a > 5)
xt::index_view(a, {{0, 0}, {1, 0}})
</code></pre>
</div>
</div>
<div class="fragment">
<div class="left-panel">
<pre class="panel"><code class="python panel" data-trim>
np.sum(a, axis=[0, 1])
np.sum(a)
np.prod(a, axis=1)
np.prod(a)
np.mean(a, axis=1)
np.mean(a)
</code></pre>
</div>
<div class="right-panel">
<pre class="panel"><code class="cpp panel" data-trim>
xt::sum(a, {0, 1})
xt::sum(a)
xt::prod(a, {1})
xt::prod(a)
xt::mean(a, {1})
xt::mean(a)
</code></pre>
</div>
</div>
</section>
<section>
<div class="splitting"></div>
<div>
<div class="left-panel">
<p style="text-align: center;"><b>Python 3 - numpy</b></p>
</div>
<div class="right-panel">
<p style="text-align: center;"><b>C++ 14 - xtensor</b></p>
</div>
</div>
<div class="fragment">
<div class="left-panel">
<pre class="panel"><code class="python panel" data-trim>
np.where(a > 5, a, b)
np.where(a > 5)
np.any(a)
np.all(a)
np.logical_and(a, b)
np.logical_or(a, b)
</code></pre>
</div>
<div class="right-panel">
<pre class="panel"><code class="cpp panel" data-trim>
xt::where(a > 5, a, b)
xt::where(a > 5)
xt::any(a)
xt::all(a)
a && b
a || b
</code></pre>
</div>
</div>
<div class="fragment">
<div class="left-panel">
<pre class="panel"><code class="python panel" data-trim>
np.absolute(a)
np.exp(a)
np.sqrt(a)
np.cos(a)
np.cosh(a)
scipy.special.erf(a)
np.isnan(a)
</code></pre>
</div>
<div class="right-panel">
<pre class="panel"><code class="cpp panel" data-trim>
xt::abs(a)
xt::exp(a)
xt::sqrt(a)
xt::cos(a)
xt::cosh(a)
xt::erf(a)
xt::isnan(a)
</code></pre>
</div>
</div>
</section>
</section>
<section>
<section>
<div class="splitting"></div>
<p style="vertical-align: top;">Lazy evaluation</p>
<div style="margin-top: 5%;">
<div class="left-panel fragment" data-fragment-index="2">
<p>res does not hold any value, nothing is evaluated ...</p>
</div>
<div class="right-panel fragment" data-fragment-index="1">
<pre class="panel"><code class="cpp panel" data-trim>
xarray<double> a, b, c;
init_tensor(a, b, c);
auto res = sqrt(cos(a) + sin(b)) * c;
</code></pre>
</div>
</div>
<div class="fragment" style="margin-top: 5%;">
<div class="left-panel" data-fragment-index="3">
<p>... until assigned to a container ...</p>
</div>
<div class="right-panel" data-fragment-index="4">
<pre class="panel"><code class="cpp panel" data-trim>
xarray<double> d = res;
// or
xarray<double> d = sqrt(cos(a) + sin(b)) * c;
</code></pre>
</div>
</div>
<div class="fragment" style="margin-top: 5%;">
<div class="left-panel" data-fragment-index="5">
<p>... or upon access</p>
</div>
<div class="right-panel" data-fragment-index="6">
<pre class="panel"><code class="cpp panel" data-trim>
// Assuming res is a 2D tensor
double d = res(4, 2);
</code></pre>
</div>
</div>
</section>
<section>
<div>
<p>So what is <code>res</code> ?</p>
</div>
<div class="fragment">
<img alt="magic.gif" src="magic.gif" width="20%"/>
</div>
<div class="fragment">
<p><code>res</code> is an <em>expression</em></p>
</div>
</section>
<section>
<img alt="expression.svg" src="expression.svg" width="50%"/>
</section>
</section>
<section>
<section>
<div class="splitting"></div>
<p>Expression system</p>
<div>
<div class="left-panel">
<p style="text-align: right;">Client code</p>
</div>
<div class="right-panel">
<pre class="panel"><code class="cpp panel" data-trim>
xarray<double> a, b, c;
init_tensor(a, b, c);
xarray<double> res = sqrt(cos(a) + sin(b)) * c;
</code></pre>
</div>
</div>
<div class="fragment" style="margin-top: 3%">
<div class="left-panel">
<p style="text-align: right;">Traditional implementation</p>
</div>
<div class="right-panel">
<pre class="panel"><code class="cpp panel" data-trim>
xarray<double> tmp1 = cos(a);
xarray<double> tmp2 = sin(b);
xarray<double> tmp3 = tmp1 + tmp2;
xarray<double> tmp4 = sqrt(tmp3);
xarray<double> res = tmp4 * c;
</code></pre>
</div>
</div>
<div class="fragment" style="margin-top: 3%;">
<div class="left-panel">
<p style="text-align: right;">xtensor implementation</p>
</div>
<div class="right-panel">
<pre class="panel"><code class="cpp panel" data-trim>
xarray<double> res(broadcast_shape(a, b, c));
for(size_t i = 0; i < res.shape()[0]; ++i)
res(i) = sqrt(cos(a(i)) + sin(b(i))) * c(i);
</code></pre>
</div>
</div>
</section>
<section>
<div class="splitting"></div>
<p>Expression system</p>
<div>
<div class="left-panel">
<p style="text-align: right;">Client code</p>
</div>
<div class="right-panel">
<pre class="panel"><code class="cpp panel" data-trim>
xarray<double> a, b, c;
init_tensor(a, b, c);
double res = (sqrt(cos(a) + sin(b)) * c)(4, 2);
</code></pre>
</div>
</div>
<div class="fragment" style="margin-top: 3%">
<div class="left-panel">
<p style="text-align: right;">Traditional implementation</p>
</div>
<div class="right-panel">
<pre class="panel"><code class="cpp panel" data-trim>
xarray<double> tmp1 = cos(a);
xarray<double> tmp2 = sin(b);
xarray<double> tmp3 = tmp1 + tmp2;
xarray<double> tmp4 = sqrt(tmp3);
xarray<double> tmp5 = tmp4 * c;
double d = tmp5(4, 2);
</code></pre>
</div>
</div>
<div class="fragment" style="margin-top: 3%;">
<div class="left-panel">
<p style="text-align: right;">xtensor implementation</p>
</div>
<div class="right-panel">
<pre class="panel"><code class="cpp panel" data-trim>
double d = sqrt(cos(a(4, 2)) + sin(b(4, 2)))
* c(4, 2);
</code></pre>
</div>
</div>
</section>
<section>
<div class="splitting"></div>
<p>Expression system</p>
<div style="margin-top: 5%;">
<div class="left-panel">
<pre class="panel"><code class="cpp panel" data-trim>
xarray<double> a, b, c, d;
auto res1 = a + b;
auto res2 = c + d;
</code></pre>
</div>
<div class="right-panel">
<img alt="expression1.svg" src="expression1.svg" width="40%"/>
</div>
</div>
<div class="fragment" style="margin-top: 10%;">
<div class="left-panel">
<pre class="panel"><code class="cpp panel" data-trim>
auto res = res1 * res2;
</code></pre>
</div>
<div class="right-panel">
<img alt="expression2.svg" src="expression2.svg" width="40%"/>
</div>
</div>
</section>
</section>
<section>
<section>
<div class="splitting"></div>
<p>Broadcasting</p>
<div style="margin-top: 2%;">
<div class="left-panel fragment">
<pre class="panel"><code class="cpp panel" data-trim>
xarray<double> a, b;
a.reshape({ 2, 3});
b.reshape({4, 2, 3});
auto r = a + b; // r.shape() ?
</code></pre>
</div>
<div class="right-panel fragment">
<pre class="panel"><code class="nohighlight panel" data-trim>
(2, 3) # a
(4, 2, 3) # b
-------------
(4, 2, 3) # r
</code></pre>
</div>
</div>
<div style="margin-top: 2%;">
<div class="left-panel fragment">
<pre class="panel"><code class="cpp panel" data-trim>
xarray<double> b;
double a;
b.reshape({4, 2, 3});
auto r = a + b; // r.shape() ?
</code></pre>
</div>
<div class="right-panel fragment">
<pre class="panel"><code class="nohighlight panel" data-trim>
() # a
(4, 2, 3) # b
-------------
(4, 2, 3) # r
</code></pre>
</div>
</div>
<div style="margin-top: 2%;">
<div class="left-panel fragment">
<pre class="panel"><code class="cpp panel" data-trim>
xarray<double> a, b;
a.reshape({ 2, 3});
b.reshape({4, 2, 1});
auto r = a + b; // r.shape() ?
</code></pre>
</div>
<div class="right-panel fragment">
<pre class="panel"><code class="nohighlight panel" data-trim>
(2, 3) # a
(4, 2, 1) # b
-------------
(4, 2, 3) # r
</code></pre>
</div>
</div>
</section>
<section>
<div class="splitting"></div>
<p>Broadcasting</p>
<div class="fragment" style="margin-top: 5%;">
<div class="left-panel">
<pre class="panel"><code class="cpp panel" data-trim>
xarray<int> a = {{1, 2, 3, 4},
{5, 6, 7, 8},
{9, 10, 11, 12}};
xarray<int> b = { 1, 3, 5, 7};
</code></pre>
</div>
<div class="right-panel">
<img alt="broadcasting4.svg" src="broadcasting4.svg" width="70%"/>
</div>
</div>
<div class="fragment" style="margin-top: 5%;">
<div class="left-panel">
<pre class="panel"><code class="cpp panel" data-trim>
xarray<int> res = a + b;
</code></pre>
</div>
<div class="right-panel">
<img alt="broadcasting5.svg" src="broadcasting5.svg" width="30%"/>
</div>
</div>
</section>
<section>
<div class="splitting"></div>
<p>Broadcasting</p>
<div style="margin-top: 2%;">
<div class="left-panel">
<pre class="panel"><code class="cpp panel" data-trim>
xarray<double> a = {1., 2., 3., 4.};
</code></pre>
</div>
<div class="right-panel">
<img alt="broadcasting1.svg" src="broadcasting1.svg" width="30%"/>
</div>
</div>
<div style="margin-top: 2%;">
<div class="left-panel fragment">
<pre class="panel"><code class="cpp panel" data-trim>
auto res = xt::broadcast(a, {3, 4});
</code></pre>
</div>
<div class="right-panel fragment">
<img alt="broadcasting2.svg" src="broadcasting2.svg" width="30%"/>
</div>
</div>
<div style="margin-top:2%;">
<div class="left-panel fragment">
<pre class="panel"><code class="cpp panel" data-trim>
xarray<double> a, b, c;
init_arrays(a, b, c);
auto res = broadcast(a + b * c, {3, 4});
</code></pre>
</div>
<div class="right-panel fragment">
<img alt="broadcasting3.svg" src="broadcasting3.svg" width="30%"/>
</div>
</div>
</section>
</section>
<section>
<section>
<div class="splitting"></div>
<p>Views</p>
<div style="margin-top: 4%;">
<div class="left-panel fragment">
<pre class="panel"><code class="cpp panel" data-trim>
xarray<int> a = {{1, 2, 3, 4},
{5, 6, 7, 8},
{9, 10, 11, 12}};
auto res = view(a, range(0, 3, 2),
range(0, 3, 2));
</code></pre>
</div>
<div class="right-panel fragment">
<img alt="view1.svg" src="view1.svg" width="30%"/>
</div>
</div>
<div style="margin-top: 4%;">
<div class="left-panel fragment">
<pre class="panel"><code class="cpp panel" data-trim>
a(0, 0) = 0;
assert(res(0, 0) == 0);
res(1, 1) = 20;
assert(a(2, 2)) == 20);
</code></pre>
</div>
<div class="right-panel fragment">
<img alt="view2.svg" src="view2.svg" width="30%"/>
</div>
</div>
</section>
<section>
<div class="splitting"></div>
<p>Views</p>
<div style="margin-top: 4%;">
<div class="left-panel fragment">
<pre class="panel"><code class="cpp panel" data-trim>
xarray<int> a = {{1, 2, 3, 4},
{5, 6, 7, 8},
{9, 10, 11, 12}};
auto res = view(a, 1, all());
</code></pre>
</div>
<div class="right-panel fragment">
<img alt="view3.svg" src="view3.svg" width="30%"/>
</div>
</div>
<div style="margin-top: 4%;">
<div class="left-panel fragment">
<pre class="panel"><code class="cpp panel" data-trim>
xarray<int> a = {{1, 2, 3, 4},
{5, 6, 7, 8},
{9, 10, 11, 12}};
auto res = view(a, 1, range(1, _));
</code></pre>
</div>
<div class="right-panel fragment">
<img alt="view4.svg" src="view4.svg" width="30%"/>
</div>
</div>
</section>
<section>
<div class="splitting"></div>
<p>Views</p>
<div>
<div class="left-panel fragment">
<pre class="panel"><code class="cpp panel" data-trim>
xarray<int> a = {{21, 2, 3, 4},
{ 5, 6, 27, 8},
{ 9, 10, 31, 12}};
auto res = indexview(a, {{0, 0},
{1, 2},
{2, 2}});
</code></pre>
</div>
<div class="right-panel fragment">
<img alt="view5.svg" src="view5.svg" width="60%"/>
</div>
</div>
<div class="fragment">
<div class="left-panel">
<pre class="panel"><code class="cpp panel" data-trim>
xarray<int> a = {{21, 2, 3, 4},
{ 5, 6, 27, 8},
{ 9, 10, 31, 12}};
auto res = filter(a, a > 20);
</code></pre>
</div>
<div class="right-panel">
<img alt="view5.svg" src="view5.svg" width="60%"/>
</div>
</div>
<div>
<div class="left-panel fragment">
<pre class="panel"><code class="cpp panel" data-trim>
res += 5;
</code></pre>
</div>
<div class="right-panel fragment">
<img alt="view6.svg" src="view6.svg" width="60%"/>
</div>
</div>
</section>
</section>
<section>
<div class="splitting"></div>
<p>Missing values</p>
<div class="fragment" style="margin-top: 5%;">
<div class="left-panel">
<pre class="panel"><code class="cpp panel" data-trim>
xtensor_optional<int> a =
{{ 1, 2 },
{ 3, missing<int>() }};
xtensor<int> b = {{ 1, 2 },
{ 3, 4 }};
</code></pre>
</div>
<div class="right-panel">
<img alt="missing_values1.svg" src="missing_values1.svg" width="60%"/>
</div>
</div>
<div class="fragment" style="margin-top: 5%;">
<div class="left-panel">
<pre class="panel"><code class="cpp panel" data-trim>
auto res = a + b;
auto hv = has_value(a + b);
</code></pre>
</div>
<div class="right-panel">
<img alt="missing_values2.svg" src="missing_values2.svg" width="60%"/>
</div>
</div>
</section>
<section>
<h4>How do I get it?</h4>
<div style="width: 70%; margin: auto;">
<div>
<img alt="conda.svg" src="conda.svg" width="40px" style="float: left;"/>
<p style="text-align: left;">With conda</p>
<pre class="panel">
<code class="python">
conda install xtensor -c conda-forge
conda install xtensor-python -c conda-forge
</code>
</pre>
</div>
<div>
<img alt="debian.svg" src="debian.svg" width="40px" style="float: left;"/>
<p style="text-align: left;">With Debian (soon)</p>
<pre class="panel">
<code class="python">
apt-get install xtensor-dev
apt-get install xtensor-python-dev
</code>
</pre>
</div>
<div>
<img alt="cmake.svg" src="cmake.svg" width="40px" style="float: left;"/>
<p style="text-align: left;">From source with cmake</p>
<pre class="panel">
<code class="python">
cmake -DCMAKE_INSTALL_PREFIX=/path/to/prefix /source/dir
make install
</code>
</pre>
</div>
</section>
<section>
<h3>How do I try it without installing anything?</h3>
<p>http://quantstack.net/xtensor</pre>
<div>
<img alt="QuantStack website" src="website.png" width="55%"/>
</div>
</section>
<section>
<h3>A C++ notebook</h3>
<div>
<img alt="Notebook Screenshot" src="notebook-screenshot.png" width="50%"/>
</div>
</section>
<section>
<h3>Authoring Python extensions</h3>
<p>C++: Using an algorithm from the STL on a numpy array</p>
<pre class="panel">
<code class="cpp">
#include <numeric> // Standard library import for std::accumulate
#include "pybind11/pybind11.h" // Pybind11 import to define Python bindings
#include "xtensor/xmath.hpp" // xtensor import for the C++ universal functions
#define FORCE_IMPORT_ARRAY // numpy C api loading
#include "xtensor-python/pyarray.hpp" // Numpy bindings
double sum_of_sines(xt::pyarray<double> &m)
{
auto sines = xt::sin(m);
// sines does not actually hold any value, which are only computed upon access
return std::accumulate(sines.cbegin(), sines.cend(), 0.0);
}
PYBIND11_PLUGIN(xtensor_python_test)
{
xt::import_numpy();
pybind11::module m("xtensor_python_test", "Test module for xtensor python bindings");
m.def("sum_of_sines", sum_of_sines,
"Computes the sum of the sines of the values of the input array");
return m.ptr();
}
</code>
</pre>
<p>Python</p>
<pre class="panel">
<code class="python">
import numpy as np
import xtensor_python_test as xt
a = np.arange(15).reshape(3, 5)
xt.sum_of_sines(v)
</code>
</pre>
</section>
<section>
<h3>Authoring Python extensions</h3>
<p>C++: Create a universal function from a C++ scalar function</p>
<pre class="panel">
<code class="cpp">
#include "pybind11/pybind11.h"
#define FORCE_IMPORT_ARRAY
#include "xtensor-python/pyvectorize.hpp"
#include <numeric>
#include <cmath>
namespace py = pybind11;