On Thu, 03 Mar 2011 19:04:44 +0000 "Phil Endecott" <spam_from_boost_dev@chezphil.org> wrote:
[...] The docs' front page has a link under "Detailed Usage Information" to "Fixed-Length Integers" - which is not really very detailed, and has examples in the notes like "integer_t<8>" that don't work. I established quickly enough that the correct syntax is integer_t<fixedlength<8>>.
Apologies, that was left over from an earlier iteration of the library and has now been corrected.
Also I noted that the conventions here don't match the built-in (u)intN_t types, i.e. int64_t vs. int63_t and the "wrap-around" behaviour. Perhaps there is some rationale for this, but I would be happier to see it consistent with the built-in types. [...]
Sorry, but the library doesn't use two's complement representation (there's no high-bit on arbitrary-length integers, so it can't), so that would only be possible with code specifically written for fixed-length integers.
[...] It seems to me that that is several hundred times faster than the Xint code (on my 1.2 GHz ARM test system). [...] This is about half the speed of the assembler, but still hundreds of times faster than the Xint code. [...]
I'll be happy to accept patches.
I don't want to write a review that says "This library doesn't do what I want, therefore it should be rejected". No doubt others will find applications where it will be useful. But I think the performance when used for fixed-size integers should be investigated.
Fixed-size integers are definitely second-class citizens right now, simply due to time and manpower constraints. As the library matures, I think you'll see serious efficiency improvements. -- Chad Nelson Oak Circle Software, Inc. * * *