4 ms·

It got me thinking as well, so I ventured and did some experiments on this, and found that the main difference is the algorithm used for the RNG; C's std lib us

by niofis 7y ago

It got me thinking as well, so I ventured and did some experiments on this, and found that the main difference is the algorithm used for the RNG; C's std lib uses a slower one (which also is thread safe, and butchered OpenMP performance). You can take a look at a more apples to apples comparison in the latest update for crb.c which uses a xor128 rng; rust is still a little faster (especially when going multithreaded), but not quite the difference in the README file, still need to get some time to update it.

bjourne 7y ago
Have you tried passing everything by value? That is, instead of: bool hit_sphere(const struct sphere* sp, const struct ray* ray, struct hit* hit) you write: static bool hit_sphere(struct sphere sp, struct ray ray, struct hit hit) IME, clang is insanely good at optimizing pass by value calls.
- hackerpacker 7y ago
  fwiw, I took a stab at replacing a bunch of => with . and ran it: time ./crb-vec-omp real 0m0.764s which is more than twice as fast as the rust example, but it didn't create the right output... if you get bored would you mind taking a stab at adding parallel and modifying crb-vec.c https://github.com/niofis/raybench https://github.com/niofis/raybench , I definitely think you might be on to something here.
deleted 7y ago
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hackerpacker 7y ago
fwiw, I looked at some of the quicker c/rust examples, without too much other analysis crb-vec-omp //I added some #pragma omp to crb-vec executable size: 18k time: real 0m3.630s valgrind: ==17703== HEAP SUMMARY: ==17703== in use at exit: 7,408 bytes in 15 blocks ==17703== total heap usage: 20 allocs, 5 frees, 14,790,856 bytes allocated rsrb_alt_mt.rs executable size: 426k time: real 0m1.630s valgrind: ==7221== HEAP SUMMARY: ==7221== in use at exit: 43,120 bytes in 216 blocks ==7221== total heap usage: 256 allocs, 40 frees, 11,113,784 bytes allocated and because we have a number of tiny single cpu vm's out there (which would also benefit from a performant language) I gave it a shot there: :~# time ./rsrb_alt_mt ./rsrb_alt_mt: /lib64/libc.so.6: version `GLIBC_2.18' not found (required by ./rsrb_alt_mt) real 0m0.002s user 0m0.002s sys 0m0.000s :~# time ./crb-vec-omp real 0m24.234s user 0m24.160s sys 0m0.035s so rust appears broken on centos 7.5 (no, I'm not going to edit the binary). But that is an insta-deal breaker for us.

by niofis 7y ago

bjourne 7y ago

Have you tried passing everything by value? That is, instead of: bool hit_sphere(const struct sphere* sp, const struct ray* ray, struct hit* hit) you write: static bool hit_sphere(struct sphere sp, struct ray ray, struct hit hit) IME, clang is insanely good at optimizing pass by value calls.

hackerpacker 7y ago
fwiw, I took a stab at replacing a bunch of => with . and ran it: time ./crb-vec-omp real 0m0.764s which is more than twice as fast as the rust example, but it didn't create the right output... if you get bored would you mind taking a stab at adding parallel and modifying crb-vec.c https://github.com/niofis/raybench https://github.com/niofis/raybench , I definitely think you might be on to something here.

deleted 7y ago

[deleted]

hackerpacker 7y ago

fwiw, I looked at some of the quicker c/rust examples, without too much other analysis crb-vec-omp //I added some #pragma omp to crb-vec executable size: 18k time: real 0m3.630s valgrind: ==17703== HEAP SUMMARY: ==17703== in use at exit: 7,408 bytes in 15 blocks ==17703== total heap usage: 20 allocs, 5 frees, 14,790,856 bytes allocated rsrb_alt_mt.rs executable size: 426k time: real 0m1.630s valgrind: ==7221== HEAP SUMMARY: ==7221== in use at exit: 43,120 bytes in 216 blocks ==7221== total heap usage: 256 allocs, 40 frees, 11,113,784 bytes allocated and because we have a number of tiny single cpu vm's out there (which would also benefit from a performant language) I gave it a shot there: :~# time ./rsrb_alt_mt ./rsrb_alt_mt: /lib64/libc.so.6: version `GLIBC_2.18' not found (required by ./rsrb_alt_mt) real 0m0.002s user 0m0.002s sys 0m0.000s :~# time ./crb-vec-omp real 0m24.234s user 0m24.160s sys 0m0.035s so rust appears broken on centos 7.5 (no, I'm not going to edit the binary). But that is an insta-deal breaker for us.