“Only the teletubbies can put an elephant into a handbag.”
So, if exactly this table should be a horizontal one, you can either use the left and right margin, e.g.:
\documentclass{article}
\usepackage[utf8]{inputenc}% Not needed for a long time.
\usepackage{booktabs}
\usepackage{threeparttable}
\usepackage{lipsum}
\usepackage{siunitx}
\usepackage{acro}
\usepackage{caption}% because of using table headings
\begin{document}
\lipsum[1-3]
\begin{table}
\footnotesize
\caption{Computational results.}
\label{tab:initial_res}
\centering
\begin{threeparttable}
\centerline{\begin{tabular}{ccccccccccccc}
\toprule
& \multicolumn{4}{c}{Compact Model} & \multicolumn{8}{c}{Benders Decomposition}\\
\cmidrule(lr){2-5}\cmidrule(lr){6-13}
Instance & LB & UB & Gap$^{1}$ & Time & LB & UB & Gap & Time& \# Iterations & Time RMP & Time SP & Time IP \\
\midrule
1 & 42.21 & 45.47 & 11.10 & 72.00 & 44.77 & 44.88 & 0.23 & 33.62 & 12 & 2.86 & 33.08 & 0.84\\
2 & 41.14 & 46.88 & 12.24 & 72.00 & 45.82 & 45.88 & 0.14 & 18.65 & 89 & 2.12 & 18.30 & 0.17\\
3 & 38.73 & 43.77 & 11.52 & 72.00 & 43.34 & 43.37 & 0.08 & 14.63 & 84 & 2.34 & 14.24 & 0.07\\
4 & 86.84 & 37.10 & 16.26 & 72.00 & 95.73 & 95.80 & 0.07 & 23.45 & 88 & 2.31 & 22.92 & 1.54\\
\bottomrule
\end{tabular}}
\begin{tablenotes}
\footnotesize
\item $^1$ MIP-Gap: Relative difference between the incumbent and the current best lower bound.
\end{tablenotes}
\end{threeparttable}
\end{table}
\lipsum[4-6]
\end{document}
or
\documentclass{article}
\usepackage{booktabs}
\usepackage{threeparttable}
\usepackage{lipsum}
\usepackage{siunitx}
\usepackage{acro}
\usepackage{caption}% because of using table headings
\usepackage{scrextend}% provides addmargin
\begin{document}
\lipsum[1-3]
\begin{table}
\begin{addmargin}{-\dimeval{\marginparwidth+\marginparsep}}
\footnotesize
\caption{Computational results.}
\label{tab:initial_res}
\centering
\begin{threeparttable}
\begin{tabular}{ccccccccccccc}
\toprule
& \multicolumn{4}{c}{Compact Model} & \multicolumn{8}{c}{Benders Decomposition}\\
\cmidrule(lr){2-5}\cmidrule(lr){6-13}
Instance & LB & UB & Gap$^{1}$ & Time & LB & UB & Gap & Time& \# Iterations & Time RMP & Time SP & Time IP \\
\midrule
1 & 42.21 & 45.47 & 11.10 & 72.00 & 44.77 & 44.88 & 0.23 & 33.62 & 12 & 2.86 & 33.08 & 0.84\\
2 & 41.14 & 46.88 & 12.24 & 72.00 & 45.82 & 45.88 & 0.14 & 18.65 & 89 & 2.12 & 18.30 & 0.17\\
3 & 38.73 & 43.77 & 11.52 & 72.00 & 43.34 & 43.37 & 0.08 & 14.63 & 84 & 2.34 & 14.24 & 0.07\\
4 & 86.84 & 37.10 & 16.26 & 72.00 & 95.73 & 95.80 & 0.07 & 23.45 & 88 & 2.31 & 22.92 & 1.54\\
\bottomrule
\end{tabular}
\begin{tablenotes}
\footnotesize
\item $^1$ MIP-Gap: Relative difference between the incumbent and the current best lower bound.
\end{tablenotes}
\end{threeparttable}
\end{addmargin}
\end{table}
\lipsum[4-6]
\end{document}
or make it much smaller and use only the right margin:
\documentclass{article}
\usepackage{booktabs}
\usepackage{threeparttable}
\usepackage{lipsum}
\usepackage{siunitx}
\usepackage{acro}
\usepackage{caption}% because of using table headings
\begin{document}
\lipsum[1-3]
\begin{table}
\tiny
\caption{Computational results.}
\label{tab:initial_res}
\centering
\begin{threeparttable}
\begin{tabular}{ccccccccccccc}
\toprule
& \multicolumn{4}{c}{Compact Model} & \multicolumn{8}{c}{Benders Decomposition}\\
\cmidrule(lr){2-5}\cmidrule(lr){6-13}
Instance & LB & UB & Gap$^{1}$ & Time & LB & UB & Gap & Time& \# Iterations & Time RMP & Time SP & Time IP \\
\midrule
1 & 42.21 & 45.47 & 11.10 & 72.00 & 44.77 & 44.88 & 0.23 & 33.62 & 12 & 2.86 & 33.08 & 0.84\\
2 & 41.14 & 46.88 & 12.24 & 72.00 & 45.82 & 45.88 & 0.14 & 18.65 & 89 & 2.12 & 18.30 & 0.17\\
3 & 38.73 & 43.77 & 11.52 & 72.00 & 43.34 & 43.37 & 0.08 & 14.63 & 84 & 2.34 & 14.24 & 0.07\\
4 & 86.84 & 37.10 & 16.26 & 72.00 & 95.73 & 95.80 & 0.07 & 23.45 & 88 & 2.31 & 22.92 & 1.54\\
\bottomrule
\end{tabular}
\begin{tablenotes}
\footnotesize
\item $^1$ MIP-Gap: Relative difference between the incumbent and the current best lower bound.
\end{tablenotes}
\end{threeparttable}
\end{table}
\lipsum[4-6]
\end{document}
But note, that this is almost unreadable.
Or use a larger paper format:
\documentclass{article}
\usepackage[a3paper]{geometry}
\usepackage{booktabs}
\usepackage{threeparttable}
\usepackage{lipsum}
\usepackage{siunitx}
\usepackage{acro}
\usepackage{caption}
\begin{document}
\lipsum[1-3]
\begin{table}
\caption{Computational results.}
\label{tab:initial_res}
\centering
\begin{threeparttable}
\begin{tabular}{ccccccccccccc}
\toprule
& \multicolumn{4}{c}{Compact Model} & \multicolumn{8}{c}{Benders Decomposition}\\
\cmidrule(lr){2-5}\cmidrule(lr){6-13}
Instance & LB & UB & Gap$^{1}$ & Time & LB & UB & Gap & Time& \# Iterations & Time RMP & Time SP & Time IP \\
\midrule
1 & 42.21 & 45.47 & 11.10 & 72.00 & 44.77 & 44.88 & 0.23 & 33.62 & 12 & 2.86 & 33.08 & 0.84\\
2 & 41.14 & 46.88 & 12.24 & 72.00 & 45.82 & 45.88 & 0.14 & 18.65 & 89 & 2.12 & 18.30 & 0.17\\
3 & 38.73 & 43.77 & 11.52 & 72.00 & 43.34 & 43.37 & 0.08 & 14.63 & 84 & 2.34 & 14.24 & 0.07\\
4 & 86.84 & 37.10 & 16.26 & 72.00 & 95.73 & 95.80 & 0.07 & 23.45 & 88 & 2.31 & 22.92 & 1.54\\
\bottomrule
\end{tabular}
\begin{tablenotes}
\footnotesize
\item $^1$ MIP-Gap: Relative difference between the incumbent and the current best lower bound.
\end{tablenotes}
\end{threeparttable}
\end{table}
\lipsum[4-6]
\end{document}
or smaller margins:
\documentclass{article}
\usepackage[margin=.75in]{geometry}
\usepackage{booktabs}
\usepackage{threeparttable}
\usepackage{lipsum}
\usepackage{siunitx}
\usepackage{acro}
\usepackage{caption}
\begin{document}
\lipsum[1-3]
\begin{table}
\footnotesize
\caption{Computational results.}
\label{tab:initial_res}
\centering
\begin{threeparttable}
\begin{tabular}{ccccccccccccc}
\toprule
& \multicolumn{4}{c}{Compact Model} & \multicolumn{8}{c}{Benders Decomposition}\\
\cmidrule(lr){2-5}\cmidrule(lr){6-13}
Instance & LB & UB & Gap$^{1}$ & Time & LB & UB & Gap & Time& \# Iterations & Time RMP & Time SP & Time IP \\
\midrule
1 & 42.21 & 45.47 & 11.10 & 72.00 & 44.77 & 44.88 & 0.23 & 33.62 & 12 & 2.86 & 33.08 & 0.84\\
2 & 41.14 & 46.88 & 12.24 & 72.00 & 45.82 & 45.88 & 0.14 & 18.65 & 89 & 2.12 & 18.30 & 0.17\\
3 & 38.73 & 43.77 & 11.52 & 72.00 & 43.34 & 43.37 & 0.08 & 14.63 & 84 & 2.34 & 14.24 & 0.07\\
4 & 86.84 & 37.10 & 16.26 & 72.00 & 95.73 & 95.80 & 0.07 & 23.45 & 88 & 2.31 & 22.92 & 1.54\\
\bottomrule
\end{tabular}
\begin{tablenotes}
\footnotesize
\item $^1$ MIP-Gap: Relative difference between the incumbent and the current best lower bound.
\end{tablenotes}
\end{threeparttable}
\end{table}
\lipsum[4-6]
\end{document}
Another non-TeX but stylistic suggestion would be to split it into several tables, e.g., two for Compact Model
and Benders Decomposition
, or to reduce the table deleting some columns. I would try to split it into two tables (using package subcaption
) and decrease the column distance of the second table a little bit:
\documentclass{article}
\usepackage{booktabs}
\usepackage{threeparttable}
\usepackage{lipsum}
\usepackage{siunitx}
\usepackage{acro}
\usepackage{subcaption}
\begin{document}
\lipsum[1-3]
\begin{table}
\footnotesize
\caption{Computational results.}
\label{tab:initial_res}
\begin{subcaptionblock}{\textwidth}
\centering
\caption{Compact Model}
\begin{threeparttable}
\begin{tabular}{lcccc}
\toprule
Instance & LB & UB & Gap$^{1}$ & Time \\
\midrule
1 & 42.21 & 45.47 & 11.10 & 72.00 \\
2 & 41.14 & 46.88 & 12.24 & 72.00 \\
3 & 38.73 & 43.77 & 11.52 & 72.00 \\
4 & 86.84 & 37.10 & 16.26 & 72.00 \\
\bottomrule
\end{tabular}
\begin{tablenotes}
\item $^1$ MIP-Gap: Relative difference between the incumbent and the current best lower bound.
\end{tablenotes}
\end{threeparttable}
\end{subcaptionblock}
\bigskip
\begin{subcaptionblock}{\textwidth}
\setlength{\tabcolsep}{.75\tabcolsep}
\centering
\caption{Benders Decomposition}
\begin{tabular}{lcccccccc}
\toprule
Instance & LB & UB & Gap & Time& \# Iterations & Time RMP & Time SP & Time IP \\
\midrule
1 & 44.77 & 44.88 & 0.23 & 33.62 & 12 & 2.86 & 33.08 & 0.84\\
2 & 45.82 & 45.88 & 0.14 & 18.65 & 89 & 2.12 & 18.30 & 0.17\\
3 & 43.34 & 43.37 & 0.08 & 14.63 & 84 & 2.34 & 14.24 & 0.07\\
4 & 95.73 & 95.80 & 0.07 & 23.45 & 88 & 2.31 & 22.92 & 1.54\\
\bottomrule
\end{tabular}
\end{subcaptionblock}
\end{table}
\lipsum[4-6]
\end{document}
But with some reduction of the column headings and the column separation space, it would even fit as a single table:
\documentclass{article}
\usepackage{booktabs}
\usepackage{threeparttable}
\usepackage{lipsum}
\usepackage{siunitx}
\usepackage{acro}
\usepackage{caption}% because of using table headings
\begin{document}
\lipsum[1-3]
\begin{table}
\newcommand*{\thead}[1]{\multicolumn{1}{c}{#1}}
\footnotesize
\setlength{\tabcolsep}{.6\tabcolsep}
\caption{Computational results.}
\label{tab:initial_res}
\centering
\begin{threeparttable}
\begin{tabular}{l*6{S[table-format=2.2]}S[table-format=1.2]S[table-format=2.2]S[table-format=2.0]S[table-format=1.2]S[table-format=2.2]S[table-format=1.2]}
\toprule
& \multicolumn{4}{c}{Compact Model} & \multicolumn{8}{c}{Benders Decomposition}\\
\cmidrule(l){2-5}\cmidrule(l){6-13}
\thead{Instance} & \thead{LB} & \thead{UB} &
\thead{Gap\tnote{1}} & \thead{Time\tnote{2}} & \thead{LB} & \thead{UB} & \thead{Gap} & \thead{Time\tnote{2}} & \thead{\#\tnote{3}} & \thead{RMP\tnote{2}} & \thead{SP\tnote{2}} & \thead{IP\tnote{2}} \\
\midrule
1 & 42.21 & 45.47 & 11.10 & 72.00 & 44.77 & 44.88 & 0.23 & 33.62 & 12 & 2.86 & 33.08 & 0.84\\
2 & 41.14 & 46.88 & 12.24 & 72.00 & 45.82 & 45.88 & 0.14 & 18.65 & 89 & 2.12 & 18.30 & 0.17\\
3 & 38.73 & 43.77 & 11.52 & 72.00 & 43.34 & 43.37 & 0.08 & 14.63 & 84 & 2.34 & 14.24 & 0.07\\
4 & 86.84 & 37.10 & 16.26 & 72.00 & 95.73 & 95.80 & 0.07 & 23.45 & 88 & 2.31 & 22.92 & 1.54\\
\bottomrule
\end{tabular}
\begin{tablenotes}
\item[1] MIP-Gap: Relative difference between the incumbent
and the current best lower bound.
\item[2] Number of iterations.
\item[3] These are duration times in seconds.% Or \unit{\milli\second}?
\end{tablenotes}
\end{threeparttable}
\end{table}
\lipsum[4-6]
\end{document}
\multicolumn{1}{p{??}}{...}
and possibly manual hyphenation. Abreviations or roatetd titles are also possible. You may need to reduce\tabcolsep
as well.threeparttable
package, I recommend you replaceGap$^{1}$
withGap\tnote{1}
and replace\item $^1$
with\item[1]
.