Typeset \chapter also in two columns when writing in twocolumn mode

Question

I use

\documentclass[twocolumn]{scrreprt}

which produces a nice layout but every chapter is set in one column mode, which leads to a new page for every chapter. How can I tell latex to set chapters also in twocolumn mode.

Minimal example:

\documentclass[twocolumn]{scrreprt}
\begin{document}
\chapter{Long one column chapter text which spans whole page}
\section{Section 1 in two column mode which breaks at some point}
\chapter{Long one column chapter text which spans whole page}
\section{Section 2 in two column mode which breaks at some point}
\end{document}

Answer 1

You can use the multicol package to create the two columns. Then they also work for the chapter headings. AFAIK it is OK to wrap the whole document in a multicols environment like shown below, but I never used it with a bigger document before.

\documentclass{scrreprt}
\usepackage{multicol}
\begin{document}
\begin{multicols}{2}
\chapter{Long one column chapter text which spans whole page}
\section{Section 1 in two column mode which breaks at some point}
\chapter{Long one column chapter text which spans whole page}
\section{Section 2 in two column mode which breaks at some point}
\end{multicols}
\end{document}

---

To avoid the page break at every chapter you still need to to set \clearpage (and maybe also \cleardoublepage) locally to \relax as shown below. However, I would simply use an article class like scrartcl instead. Then you will get basically the same format but with \section as the main level heading.

\documentclass{scrreprt}
\usepackage{multicol}
\usepackage{lipsum}% for dummy text only
\begin{document}
\begin{multicols}{2}

{\let\clearpage\relax
\chapter{Long one column chapter text which spans whole page}}
\section{Section 1 in two column mode which breaks at some point}
\lipsum

{\let\clearpage\relax
\chapter{Long one column chapter text which spans whole page}}
\section{Section 2 in two column mode which breaks at some point}
\lipsum

\end{multicols}
\end{document}

Answer 2

\documentclass[twocolumn]{scrreprt}
\makeatletter
\renewcommand\chapter{\global\@topnum\z@
                    \@afterindentfalse
                    \secdef\@chapter\@schapter}
\def\@topnewpage[#1]{#1}
\makeatother
\begin{document}
\chapter{Long one column chapter text which spans whole page}
\section{Section 1 in two column mode which breaks at some point}
\chapter{Long one column chapter text which spans whole page}
\section{Section 2 in two column mode which breaks at some point}
\end{document}