2 ms·

> I would expect two compiled languages [...] to perform almost exactly the same when they're doing nothing but arithmetic operations [...] Different languages

> I would expect two compiled languages [...] to perform almost exactly the same when they're doing nothing but arithmetic operations [...] Different languages are going to have different memory models which is going to result is vastly different performance. E.g. a GC vs reference counting vs linear types. If you are doing arithmetic on something that needs to be managed (e.g. an array), you'll see differences. Some language features close the door for optimizations. E.g. the ability to dynamically add or remove methods to an object/class can make method dispatch more or less expensive. Finally, some languages have undefined behavior (e.g. what happens when there's an overflow or a division by zero) while other languages want specific behavior for the edge cases. This all affects the performance of the resulting code, even for basic arithmetic operations.

supergarfield 10y ago
These are all good points. In this case though, C doesn't have garbage collection or OO features, and (I believe) has unspecified behavior for arithmetic exceptions. I assume Fortran does the same (since it's comparably fast), so I guess I still don't really see where people expect the difference to come from.
- greglindahl 10y ago
  C and Fortran both obey IEEE 754 and have well-defined arithmetic exceptions on most platforms -- but programmers usually instruct the compilers to ignore all that in the interests of faster code. As for what the differences are, try talking to a compiler engineer. The better ones love how Fortran features like the argument aliasing rule for 100% of code makes generating fast code easier. In fact that's one of my tests for compiler engineers in interviews; if they've worked on a C/C++/Fortran compiler and can't say anything good about the challenges and opportunities of Fortran optimization relative to C/C++, then they haven't really drilled down on performance issues!

supergarfield 10y ago

These are all good points. In this case though, C doesn't have garbage collection or OO features, and (I believe) has unspecified behavior for arithmetic exceptions. I assume Fortran does the same (since it's comparably fast), so I guess I still don't really see where people expect the difference to come from.

greglindahl 10y ago
C and Fortran both obey IEEE 754 and have well-defined arithmetic exceptions on most platforms -- but programmers usually instruct the compilers to ignore all that in the interests of faster code. As for what the differences are, try talking to a compiler engineer. The better ones love how Fortran features like the argument aliasing rule for 100% of code makes generating fast code easier. In fact that's one of my tests for compiler engineers in interviews; if they've worked on a C/C++/Fortran compiler and can't say anything good about the challenges and opportunities of Fortran optimization relative to C/C++, then they haven't really drilled down on performance issues!