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Mike Pall wrote:
Alexander Gladysh wrote:To be able to embed LJ2 into a 64-bit application would really help us. Also, can you elaborate a bit more on what effect we should expect if LJ2 would use 64-bit-specific features? Would it run noticeably faster, for example? (Sorry, that was, probably, already discussed; a link would do.)There probably won't be a significant speed difference. Having more registers is helpful in some cases. But it won't affect most benchmarks.
actually it's the number of registers that matters for tex (i did several tests on our fast servers and it really matters)
interesting is that when you run tex in a virtual machine, it actually runs at native speed probably because much fileio happens on the main machine using another core; te xitselve does not use multiple cores but future versions of luatex might delegate the pdf generation part to another thread
for tex small trees also matter (and the minimals are small)in mkiv i don't use the normal kpse file searching either but all is done by lua (so we can also read from zip filea and sockets if needed)
in mk.pdf (on the website, dev history of mkiv/luatex) there are some stats ... for instance metafun (365 pages with 1700 runtime mp graphics and a bunch of subruns) takes some 40 sec per run which is not that bad given the complexity
The main reason why regular C apps run faster on x64 than on x86 is due to better C calling conventions and RIP-relative addressing (esp. helpful for -fPIC). But LJ2 code generation doesn't depend on these for internal linkage. The main reason why regular C apps run slower on x64 than on x86 is due to the bigger pointer size which reduces the available memory bandwidth. But LJ2 uses 32 bit pointers for its GC objects on both platforms.
you mean luajit? luatex has no lj2 built in (because it is stil quite beta and because it is not available on all architectures)
Hans
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