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<ol class="chapter"><li class="chapter-item expanded "><a href="../../index.html" class="active"><strong aria-hidden="true">1.</strong> Introduction</a></li><li class="chapter-item expanded "><a href="language.html"><strong aria-hidden="true">2.</strong> DiffSL Language</a></li></ol>
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<h1 class="menu-title">DiffSL</h1>
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<h1 id="diffsl"><a class="header" href="#diffsl">DiffSL</a></h1>
<p>A compiler for a domain-specific language for ordinary differential equations (ODEs) of the following form:</p>
<p>$$
M(t) \frac{d\mathbf{u}}{dt} = F(\mathbf{u}, t)
$$</p>
<p>As an example, the following code defines a classic DAE testcase, the Robertson
(1966) problem, which models the kinetics of an autocatalytic reaction, given
by the following set of equations:</p>
<p>$$
\begin{align}
\frac{dx}{dt} &= -0.04x + 10^4 y z \
\frac{dy}{dt} &= 0.04x - 10^4 y z - 3 \cdot 10^7 y^2 \
0 &= x + y + z - 1
\end{align}
$$</p>
<p>The DiffSL code for this problem is as follows:</p>
<pre><code>in = [k1, k2, k3]
k1 { 0.04 }
k2 { 10000 }
k3 { 30000000 }
u_i {
x = 1,
y = 0,
z = 0,
}
dudt_i {
dxdt = 1,
dydt = 0,
dzdt = 0,
}
M_i {
dxdt,
dydt,
0,
}
F_i {
-k1 * x + k2 * y * z,
k1 * x - k2 * y * z - k3 * y * y,
1 - x - y - z,
}
out_i {
x,
y,
z,
}
</code></pre>
<h2 id="diffsl-language-features"><a class="header" href="#diffsl-language-features">DiffSL Language Features</a></h2>
<p>See the <a href="#diffsl-language">DiffSL Language</a> section for a full description.</p>
<ul>
<li>Input parameters</li>
<li>Define arbitrary intermediate variables:
<ul>
<li>Scalars (double precision floating point numbers)</li>
<li>Vectors (1D arrays of scalars)</li>
<li>N-dimensional tensor of scalars</li>
<li>Sparse tensors</li>
</ul>
</li>
<li>Tensor operations:
<ul>
<li>Elementwise operations</li>
<li>Tensor contractions/matmul/translation etc via index notation</li>
</ul>
</li>
<li>Stop the simulation when a condition is met</li>
</ul>
<h2 id="dependencies"><a class="header" href="#dependencies">Dependencies</a></h2>
<p>You will need to install the <a href="https://llvm.org/">LLVM project</a>. The easiest way to
install this is to use the package manager for your operating system. For
example, on Ubuntu you can install these with the following command:</p>
<pre><code class="language-bash">sudo apt-get install llvm
</code></pre>
<h2 id="installing-diffsl"><a class="header" href="#installing-diffsl">Installing DiffSL</a></h2>
<p>You can install DiffSL using cargo. You will need to indicate the llvm version you have installed using a feature flag. For example, for llvm 14:</p>
<pre><code class="language-bash">cargo add diffsl --features llvm14-0
</code></pre>
<p>Other versions of llvm are also supported given by the features <code>llvm4-0</code>, <code>llvm5-0</code>, <code>llvm6-0</code>, <code>llvm7-0</code>, <code>llvm8-0</code>, <code>llvm9-0</code>, <code>llvm10-0</code>, <code>llvm11-0</code>, <code>llvm12-0</code>, <code>llvm13-0</code>, <code>llvm14-0</code>, <code>llvm15-0</code>, <code>llvm16-0</code>, <code>llvm17-0</code>.</p>
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