Here is my late review. Apologies for the delays. What is your evaluation of the design? Boost.Multiprecision is interesting as it brings boost into area of computer science where it is not very present yet. Providing a high-level fixed/arbitrary precision integer/float type library to numerical scientist is a great move. The library is easy to use and behaves as one could expect when looking at the function name or operator. One can thus easily move any mathematical calculation from a usual POD double to a cpp_dec_float or mpf_float. A beginner will understand rapidly what a given piece of code using this library does. I especially like the wrapper around GMP which is a standard among numerical scientists. The conversions are however sometimes tricky to understand but I do not know if there is a solution to this issue which would satisfy everyone in every situation. What is your evaluation of the implementation? As already mentioned, I really like the ability to use pre-existing libraries such as GMP which are well-known and well-tested. The speed difference is really minimal and is probably worth the comfort. All functions do what you expect and the list of supported functions and constants is really comprehensive. Everyday use should be a problem. The support of numeric_limits is also a good thing for re-use in other libraries. The decomposition in front-end and back-end is particularly good for future extensions. The optional use of expression template is a great feature. The proposed improvements present on the TODO list aiming at improving the speed of the implementation will reduce the difference between cpp_int and the GMP equivalent even further. What is your evaluation of the documentation? The documentation is really comprehensive and presents interesting examples. The tricky points (conversions, ... ) are discussed and a beginner should be able to write a code without loosing his time reading an obscure documentation What is your evaluation of the potential usefulness of the library? Useful to anyone needing high precision mathematical computations. Did you try to use the library? With what compiler? Did you have any problems? Used with GCC 4.6 and ICC 12.1 to test my own library proposal (complex numbers). No problems nor warnings. The results obtained always agreed with the values given by Maple. As mentioned by others, one must still be careful with conversions. But any user of extended precision libraries should be aware of these caveats anyway. Furthermore, these are well documented. It was easy to use the cpp_dec_float or gmp_float classes in the context of complex numbers. How much effort did you put into your evaluation? A glance? A quick reading? In-depth study? Good effort at understanding and testing most of the floating point library in the context presented above. Tested the integer types for this review. Are you knowledgeable about the problem domain? Yes. See the extended complex number class proposal. Do you think the library should be accepted as a Boost library? If boost wants to move into the realm of extended precision numbers, then yes. Lastly, please consider that John and Christopher have compiled a TODO list [1] based on pre-review comments. Feel free to comment on the priority and necessity of such TODO items, and whether any might be show-stoppers or warrant conditional acceptance of the library. In my opinion, these are not show-stoppers. Adding more back-ends is always good but the main library in this field (GMP) can already be used. So this should not be a reason to reject this library. The same is true with the possible improvements to cpp_int_backend. Users wanting a really fast code can use the GMP back-end. Users in the real world may also make suggestions for other possible improvements or express their needs. Having a version of this library in the real world is a good thing to spot its possible weaknesses and will also allow the authors to work on the elements of their TODO lists. Regards, Matthieu -- Matthieu Schaller