On Mon, Jan 18, 2010 at 7:49 AM, Yue Li <xyly781@gmail.com> wrote:
I'm a user of OpenAxiom computer algebra system. Today I used ECL cvs
version (10.1.1) with multithreads enabled to build OpenAxiom.[...]
It seems that by enabling multhreads gave a big slow down ;-(

Yes, multithreading costs a huge factor because of several factors: binding of special variables, keeping an environment local to each thread, etc. For instance the lisp environment has to be stored in a thread-local storage and that costs _a lot_ to make in multiple systems -- it is absurd, but it is at least a function call for _every_ use of that storage in _every_ C function. Since we do not have the liberty to reserve a register for that purpose or having a hard-coded address for the translation table  (why the hell doesn't the ELF loaded do this?) the overal result is a slowdown of every function that uses resources such as the multiple values return array, the lisp stack, special variable bindings...

Juanjo

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