11 ms·

I think it is rare, but isn't impossible. I remember in the 2000's watching someone do a demo of Java/JVM beating the pants off a C++ application. If I remember

I think it is rare, but isn't impossible. I remember in the 2000's watching someone do a demo of Java/JVM beating the pants off a C++ application. If I remember correctly, it was something about how the JIT was doing an optimization that you would have had to write assembly in order to optimize it to the same level.

nurettin 3y ago
There were coding competition benchmarks at the time putting javac against the underdeveloped gcc 2.95 of the time. The trick they did with java programs was to allocate a region of memory only once and reuse that whenever they needed more, simulating a stack. Then the programs were benchmarked as hot start and cold start. Hot start timings were used to bench against C++ programs. If the algorithm they used was better, this sometimes resulted in head to head or better performance.
- latchkey 3y ago
  I remember that one too, but this one was not just the hot memory trick, which seems relatively easy. It was entirely JIT based, where the JIT happened to pick a better path than gcc.
thayne 3y ago
There are at least two reasons I can think of why a JIT language with GC can outperform C/c++: 1. Memory management with a GC often has higher throughput. With the downside that you can have high latency when a garbage collection occurs. 2. The JIT compilation can potentially do a better job of optimizing, because it has information about how the code has been run so far. It is possible for c or c++ (or rust) to get get the first using alternative memory management strategies, and the second by hand optimizing, and/or using profile guided optimization.
- pjmlp 3y ago
  3. The runtime also supports C++, and one emits the same MSIL code sequence that the C++ compiler would generate. Which is why WASM isn't that great novelty for grey beards.
- monocasa 3y ago
  I've also seen GC reliant concurrent algorithms that would require a lot more synchronization to keep track of when to actually free an object. GCed languages can just forget about the object and rely on the GC later to figure out what threads have access to valid objects. C and C++ need to figure out if it's safe to free.

nurettin 3y ago

There were coding competition benchmarks at the time putting javac against the underdeveloped gcc 2.95 of the time. The trick they did with java programs was to allocate a region of memory only once and reuse that whenever they needed more, simulating a stack. Then the programs were benchmarked as hot start and cold start. Hot start timings were used to bench against C++ programs. If the algorithm they used was better, this sometimes resulted in head to head or better performance.

latchkey 3y ago
I remember that one too, but this one was not just the hot memory trick, which seems relatively easy. It was entirely JIT based, where the JIT happened to pick a better path than gcc.

thayne 3y ago

There are at least two reasons I can think of why a JIT language with GC can outperform C/c++: 1. Memory management with a GC often has higher throughput. With the downside that you can have high latency when a garbage collection occurs. 2. The JIT compilation can potentially do a better job of optimizing, because it has information about how the code has been run so far. It is possible for c or c++ (or rust) to get get the first using alternative memory management strategies, and the second by hand optimizing, and/or using profile guided optimization.

pjmlp 3y ago
3. The runtime also supports C++, and one emits the same MSIL code sequence that the C++ compiler would generate. Which is why WASM isn't that great novelty for grey beards.
monocasa 3y ago
I've also seen GC reliant concurrent algorithms that would require a lot more synchronization to keep track of when to actually free an object. GCed languages can just forget about the object and rely on the GC later to figure out what threads have access to valid objects. C and C++ need to figure out if it's safe to free.