I think generally the libraries in Java help programmers use data structures that make the language seem faster (trees/hashes) .
These structures exist in c++ but aren't as easy to use so aren't used as frequently.
Those processors extensions will make mathy c++ code significantly faster. When I was on an ada project all the mathy code was written in c/c++ for speed. Pretty amazing the difference.
What? C++ comes with robust trees & hashes via the STL, along with a pretty extensive library of algorithms that work on all the STL containers. And, unlike Java, C++ lets you pack value objects contiguously in memory, which can be a massive performance win due to better cache behavior/no pointer chasing.
And, unlike Java, C++ lets you pack value objects contiguously in memory, which can be a massive performance win due to better cache behavior/no pointer chasing.
Certainly, and it is one of the features that I am often missing in Java. Rather than having an array of structs, you need to make n parallel arrays, where n is the number of struct fields. And sometimes such hacks are necessary to make things compact and fast.
But I do understand why they don't provide value types. Say, that I am allocating an array of foobar_t. And foobar_t is defined in another library. If the author of the other library changes the layout of foobar_t, you get ABI breakage. This is what brought the whole PIMPL/d-pointer mess that is often necessary in C++ and to some extend C libraries.
IBM's Java 7 and 8 beta's already have this. It's called Packed Objects and it lets you have have high density data with no pointer chasing along with a much cleaner interface to off-heap languages like C/C++/C# and even languages like Fortran/COBOL etc.
