[uecker]

"breaks completely"

I rather would say it works nicely in auto-generating the complex indexing operation for n-dimensional arrays which makes it a lot more convenient and less error-prone to write such code. The compiler may also flatten a loop.

The array of pointer hack used previously to similate 2d arrays using an array to pointers to arrays should not be used outside of special algorithms, as it is error prone and slow.

[fooker]

> The compiler may also flatten a loop.

http://c2.com/cgi/wiki?SufficientlySmartCompiler

In practice, C compilers are still notoriously bad at loop optimizations.

Polyhedral optimizations provided some hope, but no compiler managed to adopt it in production.

[uecker]

Maybe, but also irrelevant to the discussion because whether you write mat[b * A + a] by hand or mat[b][a] and let the compiler frontend expand then makes no difference to the optimizer.

[fooker]

You missed the point.

Those two representations are equivalent, yes. But that's not what flattening loops mean.

[uecker]

You are telling me what my point was?