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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 Jav

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.

pjmlp 13y ago
Being discussed for Java 9 and already available on IBM J9 JVM. http://www.slideshare.net/mmitran/ibm-java-packed-objects-mmit-20121120 http://www.slideshare.net/mmitran/ibm-java-packed-objects-mm...
danieldk 13y ago
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.
- cageface 13y ago
  For sure. Mixed value/reference semantics add a lot of complexity to C++.
- n3rd 13y ago
  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. http://www.slideshare.net/mmitran/ibm-java-packed-objects-mmit-20121120 http://www.slideshare.net/mmitran/ibm-java-packed-objects-mm... and http://www.slideshare.net/ZeroTurnaround/ryan-sciampaconeruntimeinnovationnextgenninjahackingofthejvm-24613149 http://www.slideshare.net/ZeroTurnaround/ryan-sciampaconerun...
swah 13y ago
I do miss those in Go.
judk 13y ago
Why can't Java new() use a plank to allocate objects in an array, just like C++ new() can?

pjmlp 13y ago

Being discussed for Java 9 and already available on IBM J9 JVM. http://www.slideshare.net/mmitran/ibm-java-packed-objects-mmit-20121120 http://www.slideshare.net/mmitran/ibm-java-packed-objects-mm...

danieldk 13y ago

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.

cageface 13y ago
For sure. Mixed value/reference semantics add a lot of complexity to C++.
n3rd 13y ago
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. http://www.slideshare.net/mmitran/ibm-java-packed-objects-mmit-20121120 http://www.slideshare.net/mmitran/ibm-java-packed-objects-mm... and http://www.slideshare.net/ZeroTurnaround/ryan-sciampaconeruntimeinnovationnextgenninjahackingofthejvm-24613149 http://www.slideshare.net/ZeroTurnaround/ryan-sciampaconerun...

swah 13y ago

I do miss those in Go.

judk 13y ago

Why can't Java new() use a plank to allocate objects in an array, just like C++ new() can?