[Tex/LaTex] Missing $ inserted. on a math algorithm

algorithm2ealgorithms

I've made the following pseudocode:

\documentclass[]{article}
\usepackage[]{algorithm2e}

\begin{document}

\title{Title}
\author{Author}
\date{Today}
\maketitle

\begin{algorithm}[H]
pseudoalgoritmo GRASP(maxIt, seed)\;
 \For{k = 1, ..., itmax }{
solucion \leftarrow faseConstructiva(seed):\;

solucion \leftarrow busquedaLocal(solucion);\;

ActualizarSolucion (solucion, mejorSolucion)\;
}
return mejorSolucion\;
\caption{Pseudoalgoritmo GRASP}
\end{algorithm}

\end{document}

And I'm getting the Missing $ inserted. <inserted text> error at the line where the forstatement closes. How can I fix it? Thanks in advance.

Best Answer

How 1010011010 user said, you must use $\leftarrow$ instead of \leftarrow.

Related Solutions

[Tex/LaTex] How to align text within an algorithm environment

Here tabularx package is proposed to achieve the 2 objectives. Three columns are assigned with different property {l>{$}c<{$}X}. Further, .xx\textwidth can be changed via decimal number .xx.

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Codes

\documentclass[11pt]{article}
\usepackage{algorithm2e}
\usepackage{tabularx}

\begin{document}
\begin{algorithm}
\caption{Algorithm}
\begin{tabularx}{\textwidth}{l>{$}c<{$}X}
Let &     X  & be the set of $ n $ training patterns $ x_{1}, x_{2}, \dots x_{n} $\\
    & W  &be a $ p \times q $ grid of units $ w_{ij} $ where $ i $ and $ j $ are their coordinates on that grid\\
    &  \alpha  & be the learning rate, assuming values in $ [0,1] $, initialized to a given initial learning rate\\
      &  r  & be the radius of the neighborhood function $ h(w_{ij},w_{mn},r )$, initialized to a given initial radius
\end{tabularx}
   \Repeat{$ \alpha $ reaches 0}{
     \For{$ k=1 $ to $  n $}{
       For all $ w_{ij} \in W $, calculate $ d_{ij} = || x_{k} - w_{ij} || $\;
       Select the unit that minimizes $d_{ij}$ as the winner $ w_{winner} $\;
       Update each unit $ w_{ij} \in W: w_{ij} = w_{ij} +  \alpha  h(w_{winner}, w_{ij}, r) || x_{k} - w_{ij} || $\;
     Decrease the value of $ \alpha $ and $ r $
    }
   }
\end{algorithm}
\end{document}

[Tex/LaTex] algorithm2e missing $ inserted. $ \caption

The following replicates the expected output:

\documentclass{article}

\usepackage{amsmath}

\usepackage[noline,ruled]{algorithm2e}
\setlength{\algomargin}{7.5pt}

\begin{document}

\begin{algorithm}[H]
 \caption{Stochastic Gradient Descent (SGD)}
  \KwIn{Training data $S$, regularization parameters $\lambda$, learning rate $\eta$, initialization $\sigma$}
  \KwOut{Model parameters $\Theta = (w_0,\mathbf{w},\mathbf{V})$}
  $w_0 \leftarrow 0$; $\mathbf{w} \leftarrow (0,\dots,0)$; $\mathbf{V} \sim \mathcal{N}(0,\sigma)$\; 
  \Repeat{stopping criterion is not met}{
    \For{$(x,y) \in S$}
    {
      $w_0 \leftarrow w_0 - \eta(\frac{\partial}{\partial w_0} l( y(\mathbf{x} \mid \Theta), y) + 2\lambda^0 w_0)$\;
      \For{$i \in \{1,\dots,p\} \wedge x_i \neq 0$}
      {
        $w_i \leftarrow w_i - \eta(\frac{\partial}{\partial w_i} l( y(x \mid \Theta), y) + 2\lambda_{\pi}^w w_i)$\;
        \For{$f \in \{1,\dots,k\}$}     
        {
          $v_{i,f} \leftarrow v_{i,f} - \eta(\frac{\partial}{\partial v_{i,f}} l( y(x \mid \Theta), y) + 2\lambda_{f,\pi(i)}^v v_{i,f})$\;
        }
      }
    }
  }
\end{algorithm}

\end{document}

Some considerations:

Input and output can be specified using \KwIn and \KwOut, respectively.
Math object that should be bold (like vectors) are typically set using \mathbf (or \bm, needs \usepackage{bm} after \usepackage{amsmath}).
Use \repeat rather than \while in order for the loop condition to be specified at the end.
Math mode is required for math-related content. This often goes for unicode input like λ, η and σ.
Use \mid instead of | to provide conditional functionality.
Nest \Fors to have their structure tier in the output.
Use \dots rather than ellipses ... inside math.

Best Answer

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[Tex/LaTex] How to align text within an algorithm environment

[Tex/LaTex] algorithm2e missing $ inserted. $ \caption

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