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Re: Extremely poor performance crunching random numbers under PIV-FC5

BankHacker wrote:

    1.- Andy told me to make my own bankhacker_random_r() function and
avoid glibc's (libc.so.6). I am going to work on it, but it is not
easy, I think.

What I meant by this was to make an empty implementation of random_r() in a tiny dynamic lib. In this way you isolate if the problems come from something glibc random_r() does, or if there is some terrible problem with dynamic libs for that processor/compiler/compile environment.

    2.- Jakub told that "On PIV, atomic instructions are horribly
expensive. Either you have preloaded some library that called
pthread_create, or your CPU is unable to do the jump around lock
prefix trick quickly." It sounds very interesting but I donĀ“t know how
to handle this ... any further explanation would be a great hint.

I didn't really understand what Jakub was telling with this (it seems that the compiler would react to expecting needing threadsafety in an expensive way?) but as I understood it the random_r() test was intended to test around this case.


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