In the last decade, Expression Templates (ET) have gained a reputation as an
efficient performance optimization tool for C++ codes. This reputation builds
on several ET-based linear algebra frameworks focused on combining both elegant
and high-performance C++ code. However, on closer examination the assumption
that ETs are a performance optimization technique cannot be maintained. In this
paper we demonstrate and explain the inability of current ET-based frameworks
to deliver high performance for dense and sparse linear algebra operations, and
introduce a new "smart" ET implementation that truly allows the combination of
high performance code with the elegance and maintainability of a
domain-specific language.Comment: 16 pages, 7 figure