How to draw this picture with tikz?

Question

I have a figure that I would like to draw in beamer and tikz. Here is the figure:

I start by doing something, but I am not progressing well. Any help?

\documentclass{beamer}

\usepackage{tikz}

\begin{document}

    \begin{frame}
        \tikz[overlay,remember picture]{\node[circle, fill=black] (s1) at (3.8, -1) {};}
        \tikz[overlay,remember picture]{\node[circle, fill=black] (s2) at (2.8, -1) {};}
        \tikz[overlay,remember picture]{\node[circle, fill=black] (s3) at (1.8, 1) {};}
        \tikz[overlay,remember picture]{\node[] (s4) at (2, 0) {All tasks};}
        \tikz[overlay,remember picture]{\draw[->,ultra thick] (3.2, 0) -- (5.8,0) {};}
    \end{frame}

\end{document} 

Answer 1

I know this is not exactly what you want, but it might at least get you started. I added some resources to the code. Unfortunately, pattern density cannot be modified easily in TikZ. I would create a clipping path and draw a bunch of dots, but that might still look too perfect.

Code

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{calc,patterns,positioning,shapes,arrows,backgrounds}
%http://tex.stackexchange.com/questions/54464/hatch-a-rectangle-in-tikz
%http://tex.stackexchange.com/questions/114646/where-is-the-pattern-list-gallery-for-pgfplots
%http://tex.stackexchange.com/questions/52372/should-tikzset-or-tikzstyle-be-used-to-define-tikz-styles
%http://tex.stackexchange.com/questions/16231/node-below-and-left-of-another-node-in-tikz
%http://tex.stackexchange.com/questions/121809/positioning-text-in-tikz-drawings
%http://tex.stackexchange.com/questions/53818/how-to-position-nodes-around-another-node-in-tikz
%http://tex.stackexchange.com/questions/130652/randomized-coordinates-in-tikz
\begin{document}
\tikzset{arrow format/.style={->,ultra thick,shorten >= 0mm, shorten <= 2mm}}
\tikzset{main format/.style={ultra thick, draw=black, ellipse, minimum height=2cm,minimum width=6cm,align=center}}
\tikzset{worker format/.style={pattern=dots, pattern color=black,ultra thick, draw=black, ellipse, minimum height=2cm,minimum width=3cm,align=center}}

\tikzset{text format/.style={fill=white,align=center,text width=2cm}}

\begin{tikzpicture}[overlay,remember picture]
\foreach \x in {1,2,...,15}{
    \draw [fill=black] (rand*2.3,rand*1) circle (1mm); }
\node [main format] (main) {} node [text format] {All tasks to be partitioned.};
\node [worker format] (worker3) at ($ (main.east) + (15:5cm) $) {} node [text format,] at (worker3) {Worker 3};
\node [worker format] (worker6) at ($ (main.east) + (345:5cm) $) {} node [text format] at (worker6){Worker 6};
\node [minimum width=3cm] (co-arrow1) at ($ (worker3)!.5!(worker6) $) {};
\draw [arrow format] (main) -- node [midway,above] {Scheduling} (co-arrow1.west);
\end{tikzpicture}
\end{document}

I was working on something like this for the clipping path. The problem is that normal tikz nodes are paths that can not be clipped, so you have to resort to using low-level pgf nodes.

  %http://tex.stackexchange.com/a/53195/13552
  \begin{scope}
    \pgfset{minimum width=5cm,minimum height=2.5cm}
    \pgfnode{ellipse}{center}{All tasks to be partitioned.}{main}{\pgfusepath{stroke,clip}}   
    \foreach \x in {1,2,...,15}{
    \draw [fill=black] (rand*2.3,rand*1) circle (1mm); }
  \end{scope}

Answer 2

I continue trying to do something and I get this. It looks fine but not as good as the original picture. (I could not plot the hand-like circle, etc.)

Here is my code:

\documentclass{beamer}

\usepackage{tikz}

\begin{document}

\begin{frame}
\begin{figure}
    \centering
    \resizebox{1\textwidth}{!}{%
    \begin{tikzpicture}
    \node[] (s1) at (2, -.5) {\textbullet};
    \node[] (s2) at (1, -.5) {\textbullet};
    \node[] (s3) at (.8, 1) {\textbullet};
    \node[] (s4) at (-.2, .81) {\textbullet};
    \node[] (s5) at (-.1, 1.2) {\textbullet};
    \node[] (s6) at (-.5, .4) {\textbullet};
    \node[] (s7) at (-1, 1) {\textbullet};
    \node[] (s8) at (.8, 0) {\textbullet};
    \node[] (s9) at (-1,0) {\textbullet};
    \node[] (s10) at (-1.6, .1) {\textbullet};
    \node[] (s11) at (-1.6, -1) {\textbullet};
    \node[] (s12) at (.6, .1) {\textbullet};
    \node[] (s13) at (-.6, .1) {\textbullet};
    \node[] (s14) at (.3, -1) {All tasks};
    \draw[->,ultra thick] (2.7, 0) -- (6.4,0) {};
    \draw[ultra thick] (0,0) ellipse (2.5cm and 1.8cm);
    \node[] (s15) at (8, 1.5) {\textbullet};
    \node[] (s16) at (7, 1.5) {\textbullet};
    \node[] (s17) at (7.8, 1) {\textbullet};
    \node[] (s18) at (6.8, .81) {\textbullet};
    \draw[ultra thick] (7.4,1.2) circle (1cm);
    \node[] (s19) at (8, -1.2) {\textbullet};
    \node[] (s20) at (8.5, -3) {\textbullet};
    \node[] (s21) at (7, -1.8) {\textbullet};
    \node[] (s22) at (8.8, -2) {\textbullet};
    \node[] (s23) at (9,-2) {\textbullet};
    \node[] (s24) at (7.8,-2.5) {\textbullet};
    \node[] (s25) at (8,-1.9) {\textbullet};
    \draw[ultra thick] (8,-2.1) circle (1.3cm);
    \end{tikzpicture}
    }
\end{figure}
\end{frame}

\end{document} 

and here is my output (screenshot):