Guillaume Melquiond <guillaume.melquiond@ens-lyon.fr> writes:
I agree the documentation should be clearer. As long as the variable of type I::traits_type::rounding is alive, then we are in a scope that is protected.
Now you're changing terms again. I thought it was "unprotected!"
The interval types are unprotected. So they have to be used in a scope that is protected.
I now understand what you mean, but find the terminology quite confusable. The docs need a better explanation.
Otherwise computations with them would lead to wrong results.
Default interval types are protected against an unadapted environment: some code modifies the environment and restores it later on, so that the library computes a correct result. But this protection is costly performance-wise. So you unprotect these types to speed up the computations that involves them. But as a consequence, you can safely do these computations only in a manually protected block.
In such a scope, floating-point computations will have strange behaviors, but computations involving unprotected intervals (they run a lot faster than computations involving correct intervals) are able to give correct results.
Because rounding for ordinary numbers is supposed to be "round-to-nearest" rather than "round up" or "round down" (at least one of which is needed for interval arithmetic)?
Right. The floating-point environment is set up at the start of the program by the C runtime, and compilers generate code that expects this environment to be untouched.
Okay, I think I understand it all, thanks. Are you planning to do something to the docs in response to all this? -- Dave Abrahams Boost Consulting www.boost-consulting.com