% System Combination
% Harish K Krishnamurthy <www.ece.neu.edu/~hkashyap/>
documentclass{article}

usepackage{tikz}
usetikzlibrary{shapes,arrows,shadows}
usepackage{amsmath,bm,times}
%%%<
usepackage{verbatim}
usepackage[active,tightpage]{preview}
PreviewEnvironment{tikzpicture}
setlengthPreviewBorder{5pt}%
%%%>

begin{comment}
:Title: System Combination
:Author: Harish K Krishnamurthy

A block diagram of system combination technique of combining several Automatic Speech Recognition Systems (ASRs) to determine best word sequence outputs is shown here. The training and validation phase are the important phases.

end{comment}

newcommand{mx}[1]{mathbf{bm{#1}}} % Matrix command
newcommand{vc}[1]{mathbf{bm{#1}}} % Vector command

begin{document}
% Define the layers to draw the diagram
pgfdeclarelayer{background}
pgfdeclarelayer{foreground}
pgfsetlayers{background,main,foreground}

% Define block styles used later

tikzstyle{sensor}=[draw, fill=blue!20, text width=5em,
    text centered, minimum height=2.5em,drop shadow]
tikzstyle{ann} = [above, text width=5em, text centered]
tikzstyle{wa} = [sensor, text width=10em, fill=red!20,
    minimum height=6em, rounded corners, drop shadow]
tikzstyle{sc} = [sensor, text width=13em, fill=red!20,
    minimum height=10em, rounded corners, drop shadow]

% Define distances for bordering
defblockdist{2.3}
defedgedist{2.5}

begin{tikzpicture}[
  hid/.style 2 args={
    rectangle split,
    rectangle split horizontal,
    draw=#2,
    rectangle split parts=#1,
    fill=#2!20,
    outer sep=1mm}]
  % draw input nodes
  foreach i [count=step from 1] in {the,blue,house,{{$<$eos$>$}}}
    node (istep) at (2*step, -2) {i};
  % draw output nodes
  foreach t [count=step from 4] in {la,casa,azul,{{$<$eos$>$}}} {
    node[align=center] (ostep) at (2*step, +2.75) {t};
  }
  % draw embedding and hidden layers for text input
  foreach step in {1,...,3} {
    node[hid={3}{red}] (hstep) at (2*step, 0) {};
    node[hid={3}{red}] (estep) at (2*step, -1) {};
    draw[->] (istep.north) -> (estep.south);
    draw[->] (estep.north) -> (hstep.south);
  }
  % draw embedding and hidden layers for label input
  foreach step in {4,...,7} {
    node[hid={3}{yellow}] (sstep) at (2*step, 1.25) {};
    node[hid={3}{blue}] (hstep) at (2*step, 0) {};
    node[hid={3}{blue}] (estep) at (2*step, -1) {};
    draw[->] (estep.north) -> (hstep.south);
    draw[->] (hstep.north) -> (sstep.south);
    draw[->] (sstep.north) -> (ostep.south);
  }
  % edge case: draw edge for special input token
  draw[->] (i4.north) -> (e4.south);
  % draw recurrent links
  foreach step in {1,...,6} {
    pgfmathtruncatemacro{next}{add(step,1)}
    draw[->] (hstep.east) -> (hnext.west);
  }
  % draw predicted-labels-as-inputs links
  foreach step in {4,...,6} {
    pgfmathtruncatemacro{next}{add(step,1)}
    path (ostep.north) edge[->,out=45,in=225] (enext.south);
  }
end{tikzpicture}
end{document}