Help for one simple diagram about genetic algorithmic

Question

I would like to produce the following diagram.

Thanks to the following comments and one example from TeXample.net, I have done the following code. There is some problems. How can I fix them ?

\documentclass{article}
    \usepackage[utf8]{inputenc}
    \usepackage{tikz}
    \usetikzlibrary{shapes,arrows}

    \tikzstyle{frame} = [
        rectangle, draw, 
        text width=2em, text centered,
        minimum height=4em
    ]
    \tikzstyle{line} = [draw, -latex']


\begin{document}

\begin{tikzpicture}[node distance = 3cm]
    \node [frame] (pop) {Population};
    \node [above of=pop, left of=pop] (init) {Initialisation};
    \node [below of=pop, left of=pop] (term) {Termination};
    \node [frame, above of=pop, right of=pop] (parents)  {Parents};
    \node [frame, below of=pop, right of=pop] (off)  {Offspring};

    \path [line] (parents) -- node[right,pos=.4] {Recombination} node[right,pos=.6] {Mutation} (off);
    \path [line] (init) |- (pop);
    \path [line] (pop) -| (term);
    \path [line] (off) -| node[below,pos=.25] {Survivor selection}(pop);
    \path [line] (pop) |- node[above,pos=.75] {Parents selection} (parents);
\end{tikzpicture}

\end{document}

Here is my huggly output !

Answer 1

I've made a couple of adjustments to the text width and node distance settings in your examples, have got to something which is nearly there, but you might want to make the arrowheads bigger?

I made the updates online using writeLaTeX, see here:

https://www.writelatex.com/37459xjfzxh

Screenshot attached Update: Thanks to whoever made the edits to the wL document, they reached the updated image shown below, which is pretty close to the desired result

\documentclass[margin=3pt]{standalone}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usetikzlibrary{arrows,shadows,positioning}

\tikzset{
  frame/.style={
    rectangle, draw, 
    text width=6em, text centered,
    minimum height=4em,drop shadow,fill=lime!40,
    rounded corners,
  },
  line/.style={
    draw, -latex',rounded corners=3mm,
  }
}

\begin{document}
\begin{tikzpicture}[font=\small\sffamily\bfseries,very thick,node distance = 4cm]
\node [frame] (pop) {Population};
\node [above=2cm, left of=pop] (init) {Initialisation};
\node [below=2cm, left of=pop] (term) {Termination};
\node [frame, above=2cm, right of=pop] (parents)  {Parents};
\node [frame, below=2cm, right of=pop] (off)  {Offspring};

\path [line] (parents)
 -- node[right,align=left,pos=.5] {Recombination\\[3mm]Mutation}
 (off);
\path [line] (init) |- (pop.170);
\path [line] (pop.190) -| (term);
\path [line] (off) -| node[below,pos=.25, align=center] {Survivor\\ selection}(pop);
\path [line] (pop) |- node[above,pos=.75, align=center] {Parents\\ selection}(parents);
\end{tikzpicture}
\end{document}