This is fast, READABLE, and accurate:
bool is_leap_year(uint32_t y) { // Works for Gregorian years in range [0, 65535] return ((!(y & 3)) && ((y % 25 != 0) || !(y & 15))); }
This impl is mentioned in TFA.. It's much slower and includes branches.
I'd expect even without optimizations on, there wouldn't be branches in the output for that code.
There are, even with optimizations on. You could have checked: https://godbolt.org/#g:!((g:!((g:!((h:codeEditor,i:(filename...
I didn't find any way to get a compiler to generate a branchless version. I tried clang and GCC, both for amd64, with -O0, -O5, -Os, and for clang, -Oz.
>READABLE
Great. It will be useful for the exhaustive tests of the faster version.
You commented out your entire function body and the closing }. Also, on 32-bit platforms, it doesn't stop working at 65535.
just a formatting issue on my side, there were \n.
This website eats newlines, unless you double them (one of the annoying features of markdown). You can use codeblocks by putting 4 spaces before each line:
int main() {
// this should be properly formatted
return 0;
};If you fix it, other people can test your code without having to fix the syntax themselves first.