From: Reza Rastak <rastak@stanford.edu>
Date: Thu, 28 May 2020 06:21:11 +0000 (-0400)
Subject: Information about constexpr capabilities of dealii added
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2a83463a2e756c7e343f5f052dc861b82f351475;p=release-papers.git

Information about constexpr capabilities of dealii added
---

diff --git a/9.2/paper.tex b/9.2/paper.tex
index f93a9ff..58393f4 100644
--- a/9.2/paper.tex
+++ b/9.2/paper.tex
@@ -235,6 +235,21 @@ that we briefly outline in the remainder of this section:
   solution. This, too, has been addressed in this release.
   \item \todo[inline]{Reza: Please add a short summary of the
     \texttt{DiscreteTime} class}
+\item Certain types of quantities in a simulation are constants fully known
+  at compile time. They can be pre-calculated and fully stored inside the
+  compiled program binary in order to avoid unnecessary initialization during
+  runtime. This optimization is now enabled for the class templates
+  \texttt{Tensor} and \texttt{SymmetricTensor} by qualifying their constructor,
+  member functions, and overloaded operators as \texttt{constexpr}.
+  For instance, the linear mechanical constitutive model for elastic solids
+  uses a constant fourth-order elasticity tensor
+  $\mathbb{C} = \lambda \boldsymbol{I} \otimes \boldsymbol{I} + 2 \mu \mathbb{I}$
+  which does not depend on the current state of strain.
+  This tensor can be statically initialized by defining it as
+  \texttt{constexpr SymmetricTensor<4, dim>}.
+  As another example, the lattice vectors in a crystal plasticity model are generally
+  constant and known during compilation time, enabling their efficient definition as
+  \texttt{constexpr Tensor<1, dim>}.
 \item z \todo[inline]{What else? Maybe mention the updated step-12?}
 \end{itemize}
 %