4 ms·

This is most probably more linked to Java/Kotlin vs Objective-C/Swift. Want an array of 1000 objects in Java ? You'll endup with 1001 allocations and 1000 point

This is most probably more linked to Java/Kotlin vs Objective-C/Swift. Want an array of 1000 objects in Java ? You'll endup with 1001 allocations and 1000 pointers.

BillinghamJ 6y ago
Pretty sure you'll end up with exactly the same in an NSArray? ObjC is excellent but it's not doing anything fundamentally magic there
- dwaite 6y ago
  In Swift you can add value types to the heap-backed array directly, in ObjC you can use stack allocated arrays (since you have all of C) and there are optimizations such as NSNumber using tagged pointers.
  - deleted 6y ago
    [deleted]
- mantap 6y ago
  Theoretically Java should be more memory efficient because it makes fewer guarantees and can move memory around. The advantage of Swift/ARC is not that it uses less memory per se but that it has a lower high water mark because memory is freed much sooner.
  - kllrnohj 6y ago
    > Theoretically Java should be more memory efficient because it makes fewer guarantees and can move memory around. Java makes a lot of memory guarantees that are hard to make efficient. Specifically in that it becomes extremely hard to have a scoped allocation. Escape analysis helps, but the nature of Java's GC'd + no value types means it's basically never good at memory efficiency. Memory performance can be theoretically good, but efficiency not really. That's just part of the tradeoff it's making. And nearly everything is behind a reference, making everything far larger than it could be. Compaction helps reduce fragmentation, but it comes at the cost of necessarily doubling the size of everything being compacted. Only temporarily, but those high-water spikes are what kicks things to swap, too.
- socialdemocrat 6y ago
  Big difference is that Objective-C is a superset of C. Any Objective-C developer worth his/her salt will drop down to C code when you need to optimize. The object-oriented parts of Objective-C are way slower than Java. But the reason Objective-C programs can still outcompete Java programs is that you have the opportunity to pick hotspots and optimize the hell out of them using C code. Object-oriented programs in Objective-C are written in a very different fashion from Java programs. Java programs tend to have very fine granularity on their objects. Objective-C programs tend to have interfaces which are bulkier, and larger objects. That is partly why you can have a high performance 3D API like Metal written in a language such as Objective-C which has very slow method dispatch. It works because the granularity of the objects have been designed with that in mind.

This is most probably more linked to Java/Kotlin vs Objective-C/Swift. Want an array of 1000 objects in Java ? You'll endup with 1001 allocations and 1000 pointers.

BillinghamJ 6y ago

Pretty sure you'll end up with exactly the same in an NSArray? ObjC is excellent but it's not doing anything fundamentally magic there

dwaite 6y ago
In Swift you can add value types to the heap-backed array directly, in ObjC you can use stack allocated arrays (since you have all of C) and there are optimizations such as NSNumber using tagged pointers.
- deleted 6y ago
  [deleted]
mantap 6y ago
Theoretically Java should be more memory efficient because it makes fewer guarantees and can move memory around. The advantage of Swift/ARC is not that it uses less memory per se but that it has a lower high water mark because memory is freed much sooner.
- kllrnohj 6y ago
  > Theoretically Java should be more memory efficient because it makes fewer guarantees and can move memory around. Java makes a lot of memory guarantees that are hard to make efficient. Specifically in that it becomes extremely hard to have a scoped allocation. Escape analysis helps, but the nature of Java's GC'd + no value types means it's basically never good at memory efficiency. Memory performance can be theoretically good, but efficiency not really. That's just part of the tradeoff it's making. And nearly everything is behind a reference, making everything far larger than it could be. Compaction helps reduce fragmentation, but it comes at the cost of necessarily doubling the size of everything being compacted. Only temporarily, but those high-water spikes are what kicks things to swap, too.
socialdemocrat 6y ago
Big difference is that Objective-C is a superset of C. Any Objective-C developer worth his/her salt will drop down to C code when you need to optimize. The object-oriented parts of Objective-C are way slower than Java. But the reason Objective-C programs can still outcompete Java programs is that you have the opportunity to pick hotspots and optimize the hell out of them using C code. Object-oriented programs in Objective-C are written in a very different fashion from Java programs. Java programs tend to have very fine granularity on their objects. Objective-C programs tend to have interfaces which are bulkier, and larger objects. That is partly why you can have a high performance 3D API like Metal written in a language such as Objective-C which has very slow method dispatch. It works because the granularity of the objects have been designed with that in mind.