Author: Miguel A. Ballicora
Date: 18:36:38 10/04/01
Go up one level in this thread
On October 04, 2001 at 19:30:34, J. Wesley Cleveland wrote: >On October 04, 2001 at 17:18:43, Robert Hyatt wrote: > >>On October 04, 2001 at 14:22:09, J. Wesley Cleveland wrote: >> >>>On October 04, 2001 at 14:03:13, Robert Hyatt wrote: >>> >>>>On October 04, 2001 at 12:40:53, J. Wesley Cleveland wrote: >>>> >>>>>Take an iterative function F(a), i.e. F1(a) = a, F2(a) = F(a), F3(a) = F(F(a)), >>>>>... Assume the function is complicated enough to use all the available registers >>>>>on your machine and requires the same number of machine cycles for each >>>>>iteration. Now find the first iteration for which F(b) > F(a). A serial >>>>>implementation will spend a significant amount of time saving and restoring >>>>>state as it goes between the two functions, while the two processor solution >>>>>will only have to spend a minimal amount of time syncronizing at the end of each >>>>>iteration (due to my second condition). >>>> >>>> >>>>Explain how you are going to do a recursive function (I assume you mean >>>>recursive and not iterative above due to the way you defined the thing) >>>>in a parallel manner. >>> >>>I wrote recursive, but it could be implemented either way. >> >> >>In the text above I see "iterative" not "recursive" >> >> >>> >>>The parallel part is that one processor calculates f1(a), f2(a), ... >>>while the other processor calculates f1(b), f2(b), ... >> >> >> >>In the text above you assume some finite number of registers. And you assume >>that on the machine you use, that is an issue. I choose to use a SPARC. >>Which means that two different functions use two different sets of registers. >>And that advantage evaporates. Or I run it on a MIPS and use 32 registers >>rather than 8. >> >[snip] > >What I am saying is that in a *real* situation, there may be significant >overhead in switching from one process to another, which will give a >super-linear speedup even though theory would predict only a linear speedup. This has not been addressed yet. Once it is admitted that time slicing is the way to go, the overhead is a theoretical obstacle to the denial of the superlinear speed up. 2.01 > 2.00. Regards, Miguel
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