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in reply to Unbelievably slow..
i slightly modified the c++ version to run it in c, declaring variables and changing cout to printf. it ran compiled (with TURBOC :) ) in 3 secs. i still can't believe there would be such a vast difference between perl and c++...so i fiddled a bit, doing extra printf, and found that for the c/c++ version the value of shift didn't seem to change, ie printf("%d",shift); prints 0's. this wasn't the case in the perl version. maybe i'm doing something wrong, but couldn't figure out why. maybe some other monk (with a C++ compiler -- i'm missing header files in my cygwin gcc) can check this. if my results were correct, then no wonder the c/c++ version ran so fast (turning the shift<<=1; into a no-op) |
Re^2: Believably slow..
by Aristotle (Chancellor) on Jun 30, 2003 at 21:20 UTC
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Even if it didn't turn that into a no-op, it won't make a whole lot of difference. A shift operation, even with loading and saving a variable from memory and then even with stack frame related overhead, will take maybe two dozen clock cycles on a bad day (cache misses et al) on modern CPUs. In comparison, even the simplest single operation in Perl will probably take a few hundred cycles (if not thousands).
If reports are to be believed though, Perl6 will be much faster at this, and native Parrot code should be on a par with C.
Makeshifts last the longest.
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