[Tex/LaTex] How to get the random seed used in a tikzpicture

randomtikz-pgf

I have a picture with randomly placed nodes. Sometimes the figure is nicer than other, and in the final version of the document, I'd like to have a nice figure.

I'd like to know how to get the seed used in each rendering of the figure and display it, so that I may use it with \pgfmathsetseed{}. I know I could manually try a bunch of different values myself and set it myself in the end, but this is a fallback solution.

Below is a sample code, the part of the figure that looks nice or not nice depending on the random number generator's seed.

\resizebox{88mm}{!}{
 \begin{tikzpicture}

\draw (0,0)[very thick] ellipse (1.5cm and 2.25cm);

 \foreach \x in {1,2,...,80}{
    \node (node\x) at (rand*1,rand*1.65) {$\bullet$};
 }

 \foreach \list in {
{66,    26, 63, 11, 10, 20, 61, 55},
{24,    10, 31, 8,  66, 4,  72, 1},
%...
} {
    \foreach \i in \list {
        \foreach \j in \list {
             \draw (node\i.center) -- (node\j.center);
        }
    }
 }

%...
%...

\end{tikzpicture}
}

How can I get the seed used by the random number generator, without setting it myself?

Best Answer

The value is stored in the counter \pgfmath@rnd@z. So you can read that off.

\documentclass[tikz]{standalone}
\makeatletter
\def\pgfcurrentseed{%
\pgfmathparse{\pgfmath@rnd@z}\pgfmathresult%
}
\makeatother
\begin{document}
\begin{tikzpicture}
\draw (0,0)[very thick] ellipse (1.5cm and 2.25cm);

\node (a) at (4,0) {Current seed is \pgfcurrentseed};
\foreach \x in {1,2,...,80}{
   \node (node\x) at (rand*1,rand*1.65) {$\bullet$};
}

\foreach \list in {
{66,26, 63, 11, 10, 20, 61, 55},
{24,10, 31, 8,  66, 4,  72, 1},
}{
  \foreach \i in \list {
    \foreach \j in \list {
       \draw (node\i.center) -- (node\j.center);
    }
  }
}
\end{tikzpicture}
\end{document}

enter image description here

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