The text input file of a simulation should be precised using the method \code{initialize} which will instantiate the static \code{Parser} object of \akantu. This section explains how to manipulate \code{Parser} objects to input data in \akantu.
\begin{cpp}
int main(int argc, char *argv[]) {
initialize("input_files.dat", argc, argv);
...
\end{cpp}
\subsection{Akantu Parser}
\akantu file parser has a tree organization.
\begin{itemize}
\item \code{Parser}, the root of the tree, can be accessed using
\begin{cpp}
Parser & parser = getStaticParser();
\end{cpp}
\item \code{ParserSection}, branch of the tree, contains map a of sub-sections (\code{SectionType}, \code{ParserSection}) and a \code{ParserSection *} pointing to the parent section. The user section of the input file can directly be accessed by
\begin{cpp}
const ParserSection & usersect = getUserParser();
\end{cpp}
\item \code{ParserParameter}, the leaf of the tree, carries data of the input file which can be casted to the correct type with
\begin{cpp}
Real mass = usersect.getParameter("mass");
\end{cpp}
or used directly within an expression
\begin{cpp}
Real dead_weight = 9.81 * usersect.getParameterValue<Real>("mass");
\end{cpp}
\end{itemize}
\subsection{Grammar}
The structure of text input files consists of different sections containing a list of parameters. As example, the file parsed in the previous section will look like
\begin{cpp}
user parameters [
mass = 10.5
]
\end{cpp}
Basically every standard arithmetic operations can be used inside of input files as well as the constant \code{pi} and \code{e} and the exponent operator \code{\^{}}. Operations between \code{ParserParameter} are also possible with the convention that only parameters of the current and the parent sections are available. \code{Vector} and \code{Matrix} can also be read according to the \code{NumPy}\cite{numpy} writing convention (a.e. cauchy$\_$stress$\_$tensor = [[$\sigma_{xx}$, $\sigma_{xy}$],[$\sigma_{yx}$,$\sigma_{yy}$]]).
An example illustrating how to parse the following input file can be found in \code{example$\backslash$io$\backslash$parser$\backslash$example$\_$parser.cc}.
The input file should also be used to specify material characteristics (constitutive behavior and material properties). The dedicated material section is then read by \code{initFull} method of \code{SolidMechanicsModel} which initializes the different materials specified with the following convention:
\begin{cpp}
material %\emph{constitutive\_law}% %\emph{<optional flavor>}% [
name = $value$
rho = $value$
...
]
\end{cpp}
\index{Constitutive\_laws} where \emph{constitutive\_law} is the adopted
constitutive law, followed by the material properties listed one by line in the
bracket (\eg \code{name} and density \code{rho}). Some constitutive laws can
also have an \emph{optional flavor}. More information can be found in sections relative to material
constitutive laws \ref{sect:smm:CL} or in Appendix \ref{app:material-parameters}.
\section{Output data}
\subsection{Generic data}
In this chapter, we address ways to get the internal data in human-readable formats.
The models in \akantu handle data associated to the
mesh, but this data can be split into several \code{Arrays}. For example, the
data stored per element type in a \code{ElementTypeMapArray} is composed of as
many \code{Array}s as types in the mesh.
In order to get this data in a visualization software, the models contain a
object to dump \code{VTK} files. These files can be visualized in software such
as \code{ParaView}\cite{paraview}, \code{ViSit}\cite{visit} or \code{Mayavi}\cite{mayavi}.
The internal dumper of the model can be configured to specify which data fields
are to be written. This is done with the
\code{addDumpField}\index{I\/O!addDumpField} method. By default all the files
are generated in a folder called \code{paraview/}
\begin{cpp}
model.setBaseName("output"); // prefix for all generated files
model.addDumpField("displacement");
model.addDumpField("stress");
...
model.dump()
\end{cpp}
The fields are dumped with the number of components of the memory. For example, in 2D, the memory has
\code{Vector}s of 2 components, or the $2^{nd}$ order tensors with $2\times2$ components.
This memory can be dealt with \code{addDumpFieldVector}\index{I\/O!addDumpFieldVector} which always dumps
\code{Vector}s with 3 components or \code{addDumpFieldTensor}\index{I\/O!addDumpFieldTensor} which dumps $2^{nd}$
order tensors with $3\times3$ components respectively. The routines \code{addDumpFieldVector}\index{I\/O!addDumpFieldVector} and
\code{addDumpFieldTensor}\index{I\/O!addDumpFieldTensor} were introduced because of \code{ParaView} which mostly manipulate 3D data.
Those fields which are stored by quadrature point are modified to be seen in the
\code{VTK} file as elemental data. To do this, the default is to average the
values of all the quadrature points.
The list of fields depends on the models (for
\code{SolidMechanicsModel} see table~\ref{tab:io:smm_field_list}).
\begin{table}
\centering
\begin{tabular}{llll}
\toprule
key & type & support \\
\midrule
displacement & Vector<Real> & nodes \\
mass & Vector<Real> & nodes \\
velocity & Vector<Real> & nodes \\
acceleration & Vector<Real> & nodes \\
force & Vector<Real> & nodes \\
residual & Vector<Real> & nodes \\
increment & Vector<Real> & nodes \\
{blocked\_dofs} & Vector<bool> & nodes \\
partitions & Real & elements \\
material\_index & variable & elements\\
strain & Matrix<Real> & quadrature points \\
Green strain & Matrix<Real> & quadrature points \\
principal strain & Vector<Real> & quadrature points \\
principal Green strain & Vector<Real> & quadrature points \\
grad\_u & Matrix<Real> & quadrature points \\
stress & Matrix<Real> & quadrature points \\
Von Mises stress & Real & quadrature points \\
material\_index & variable & quadrature points \\
\bottomrule
\end{tabular}
\caption{List of dumpable fields for \code{SolidMechanicsModel}.}
\label{tab:io:smm_field_list}
\end{table}
\subsection{Cohesive elements' data}
Cohesive elements and their relative data can be easily dumped thanks
to a specific dumper contained in
\code{SolidMechanicsModelCohesive}. In order to use it, one has just
to add the string \code{"cohesive elements"} when calling each method
already illustrated. Here is an example on how to dump displacement
It is assumed that the arrays in the map have the same sizes as the element numbers in the mesh for element types of dimension \code{spatial\_dimension}.
\begin{cpp}
ElementTypeMapArray<Real> elem_data;
elem_data.initialize(mesh,
_nb_component = 1,
_with_nb_element = true);
mesh.addDumpFieldExternal("my_field", elem_data);
\end{cpp}
\end{itemize}
If some changes have to be applied on the data as for example a padding for
\code{ParaView} vectors, this can be done by using the