[grg0]

I'd say it's being able to structure your data however suits your problem and your hardware, then being able to look at a profile and being able to map read/writes back to source. Both C and C++ excel at this.

The advantage of C++ over C is that, with care, you can write zero-cost abstractions over whatever mess your data ends up as, and make the API still look intuitive. C isn't as good here.

[uecker]

According to my experience, all the "zero-cost abstractions" from C++ most of the time make it more annoying to maintain and/or understand the code, especially with respect to resource management, introduce compatibility issues at the toolchain level, and - even when looking perfect in toy benchmarks - are often not even zero-cost (e.g. all the bloat the templates generate often hurts).

[nine_k]

Is Fortran 90 not flexible enough in defining data layout?