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Commit ec04cb8f authored by Stéphane Del Pino's avatar Stéphane Del Pino
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Add description of operators defined in the scheme module

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......@@ -3883,6 +3883,159 @@ function.
**** Operators overloading for ~Vh~ <<Vh-operators>>
The ~scheme~ module provides overload of binary operators. Since ~Vh~ is
an abstract type, some operators may not be defined (or allowed) for
concrete types.
***** Unary operators
The only supported unary operators for ~Vh~ are given in the following
table
| operator | description |
|----------+----------------------|
| ~+~ | plus unary operator |
| ~-~ | minus unary operator |
We recall that the unary ~+~ operator is a convenience operator that has
no effect.
***** Binary operators
The supported binary operators for ~vh~ data types are arithmetic
operators.
#+begin_src latex :results drawer :exports results
\begin{equation*}
\left|
\begin{array}{rl}
\mathtt{+}:& \mathbb{V}_h \times \mathbb{V}_h \to \mathbb{V}_h\\
\mathtt{-}:& \mathbb{V}_h \times \mathbb{V}_h \to \mathbb{V}_h\\
\mathtt{*}:& \mathbb{V}_h \times \mathbb{V}_h \to \mathbb{V}_h\\
\mathtt{/}:& \mathbb{V}_h \times \mathbb{V}_h \to \mathbb{V}_h
\end{array}
\right.
\end{equation*}
#+end_src
Observe that in the case of $\vec{\mathbb{P}}_0(\mathbb{R})$, the only
available operators are ~+~ and ~-~.
#+BEGIN_note
In the case of $\mathbb{P}_0$ functions, an operator is defined as soon
as it is defined for the value type.
#+END_note
For instance, one can multiply a $\mathbb{P}_0(\mathbb{R}^{2\times2})$
discrete function by a $\mathbb{P}_0(\mathbb{R}^2)$. The result is then
a $\mathbb{P}_0(\mathbb{R}^2)$ discrete function.
#+BEGIN_SRC pugs :exports both :results none
import mesh;
import scheme;
let m:mesh, m = cartesianMesh(0,[1,1],(10,10));
let A:R^2 -> R^2x2, x -> [[2*x[0], x[1]],[-x[0], 3*x[1]]];
let u:R^2 -> R^2, x -> 2*[x[0], x[1]*x[0]];
let Ah:Vh, Ah = interpolate(m, P0(), A);
let uh:Vh, uh = interpolate(m, P0(), u);
let Auh:Vh, Auh = Ah*uh;
#+END_SRC
Another illustration is: trying to add $\mathbb{P}_0(\mathbb{R})$ and
$\mathbb{P}_0(\mathbb{R}^1)$
#+NAME: invalid-Vh-sum-type
#+BEGIN_SRC pugs-error :exports both :results output
import mesh;
import scheme;
let m:mesh, m = cartesianMesh([0],[1],10);
let f:R^1 -> R, x -> 2*x[0];
let f1:R^1 -> R^1, x -> 2*x;
let fh:Vh, fh = interpolate(m, P0(), f);
let f1h:Vh, f1h = interpolate(m, P0(), f1);
fh+f1h;
#+END_SRC
produces the following error
#+results: invalid-Vh-sum-type
****** Additional ~+~ and ~-~ operators
#+begin_src latex :results drawer :exports results
\begin{equation*}
\forall \mathbb{S}, \mathbb{S}_2 \in \{\mathbb{B},\mathbb{N},\mathbb{Z},\mathbb{R},\mathbb{R}^1,\mathbb{R}^2,\mathbb{R}^3,\mathbb{R}^{1\times1},\mathbb{R}^{2\times2},\mathbb{R}^{3\times3}\},
\quad
\left|
\begin{array}{rl}
\mathtt{+}:& \mathbb{S} \times \mathbb{V}_h \to \mathbb{V}_h\\
\mathtt{-}:& \mathbb{S} \times \mathbb{V}_h \to \mathbb{V}_h\\
\mathtt{+}:& \mathbb{V}_h \times \mathbb{S} \to \mathbb{V}_h\\
\mathtt{-}:& \mathbb{V}_h \times \mathbb{S} \to \mathbb{V}_h
\end{array}
\right.
\end{equation*}
#+end_src
Let us consider the following example
#+NAME: substract-mean-value-to-Vh
#+BEGIN_SRC pugs :exports both :results output
import mesh;
import scheme;
import math;
let m:mesh, m = cartesianMesh(0,[0.3,1.1],(5,15));
let mesh_volume:R, mesh_volume = sum_of_R(cell_volume(m));
let u:R^2 -> R, x -> 2*dot(x,x);
let uh:Vh, uh = interpolate(m, P0(), u);
let uh0:Vh, uh0 = uh - (integral_of_R(uh) / mesh_volume);
cout << "integral(uh) = " << integral_of_R(uh) << "\n";
cout << "integral(uh0) = " << integral_of_R(uh0) << "\n";
#+END_SRC
Here we substract the mean value of a discrete function.
#+results: substract-mean-value-to-Vh
****** Additional ~*~ operators
The following constructions are allowed for ~*~ operator.
#+begin_src latex :results drawer :exports results
\begin{equation*}
\forall \mathbb{S} \in \{\mathbb{B},\mathbb{N},\mathbb{Z},\mathbb{R},\mathbb{R}^{1\times1},\mathbb{R}^{2\times2},\mathbb{R}^{3\times3}\},
\quad
\mathtt{*}: \mathbb{S} \times \mathbb{V}_h \to \mathbb{V}_h.
\end{equation*}
#+end_src
Obviously, if $\mathbb{S}=\mathbb{R}^{d\times d}$, for $d\in\{1,2,3\}$,
the right operand must be have a compatible type, for instance
$\mathbb{P}_0(\mathbb{R}^{d\times d})$ or $\mathbb{P}_0(\mathbb{R}^d)$.
Additionally these operators are defined
#+begin_src latex :results drawer :exports results
\begin{equation*}
\forall \mathbb{S} \in \{\mathbb{B},\mathbb{N},\mathbb{Z},\mathbb{R},\mathbb{R}^1,\mathbb{R}^2,\mathbb{R}^3,\mathbb{R}^{1\times1},\mathbb{R}^{2\times2},\mathbb{R}^{3\times3}\},
\quad
\mathtt{*}: \mathbb{V}_h \times \mathbb{S}\to \mathbb{V}_h.
\end{equation*}
#+end_src
Following logic, if for instance the right operand is an ~R^2~
expression, the left operand ~Vh~ must be of type
$\mathbb{P}_0(\mathbb{R})$ or $\mathbb{P}_0(\mathbb{R}^{2\times 2})$.
****** Additional ~/~ operators
The following operators are defined
#+begin_src latex :results drawer :exports results
\begin{equation*}
\forall \mathbb{S} \in \{\mathbb{N},\mathbb{Z},\mathbb{R}\},
\quad
\mathtt{/}: \mathbb{S} \times \mathbb{V}_h \to \mathbb{V}_h.
\end{equation*}
#+end_src
[fn:pugs-def] ~pugs~: Parallel Unstructured Grid Solvers
[fn:MPI-def] ~MPI~: Message Passing Interface
......
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