C++ expression templates performance issues in scientific computing

Ever-increasing size and complexity of software applications and libraries in parallel scientific computing is making implementation in the programming languages traditional for this field--FORTRAN 77 and C--impractical. The major impediment to the progression to a higher-level language such as C++ is attaining FORTRAN 77 or C performance, which is considered absolutely necessary by many practitioners. The use of template metaprogramming in C++, in the form of so-called expression templates to generate custom C++ code, holds great promise for getting C performance from C++ in the context of operations on array-like objects. Several sophisticated expression template implementations of parallel array-class libraries exist, and in certain circumstances their promise of performance is realized. Unfortunately this is not uniformly the case; this paper explores the major reasons that this is so