Ramine
2/16/2015 10:18:00 PM
Hello,
A guy called Grinder on usenet have presented me the results of my
benchamrk of my parallel sort library, here it is on a 12 cores and read
my explanation bellow:
---
Number of cores is: 12
Scalability with parallel mergesort on 12 cores is: 2.38
Time of parallel mergesort on one core is: 323286 microseconds
Time of parallel mergesort on 12 cores is: 135606 microseconds
Number of cores is: 12
Scalability with parallel quicksort on 12 cores is: 2.33
Time of parallel quicksort on one core is: 330408 microseconds
Time of parallel quicksort on 12 cores is: 141813 microseconds
Number of cores is: 12
Scalability with parallel heapsort on 12 cores is: 4.41
Time of parallel heapsort on one core is: 730261 microseconds
Time of parallel heapsort on 12 cores is: 165588 microseconds
--
I have took a look at the results, and i think the explanation is the
following: Since i am sorting strings, the compare's function in my
parallel sorts algorithms that compares two strings is less expensive on
your CPU, so from the Amdahl's law, since the compare's function
constitutes the parallel part of the Amdahl's law, and the memory
transfers from the memory to the L2 caches constitutes the serial part,
so since the parallel part is less expensive on your CPU than on other
CPUs , so from the Amdahl's law this is why it scales less on your CPU
than on other CPUs.
But i have to be more precise as does a scientist: the compare's
function of two strings takes less CPU time on your CPU than other CPUs,
so it scales less on more cores, but the compare's function of two
strings on your CPU is faster than on other CPUs, so even if
it scales less on more cores , the two algorithms, the serial and the
parallel, are faster on your CPU than on other CPUs, since the compare's
function of two strings is faster on your CPU than on other
CPUs, that's a good news.
Thnk you,
Amine Moulay Ramdane.