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parallel_sort syntax

Hello peoples!

So basically I have a int vector called primes:

[bash]vector primes;[/bash]

It is filled up with parallely generated primes. Now, I need to sort them. I tried using parallel_sort, but it screwed up. I've tried using pointers, iterators, pointers to iterators, etc.

Can anyone help?

Thanks!

0 Kudos
6 Replies
RafSchietekat
Black Belt
116 Views

Last time I checked, "parallely" was not a word. :-)

As for the programming issue, please ask a real question with usable information (and preferably without assigning blame to others).

(Added after #4) Smiley, parentheses.
116 Views

Oops, double post. Use the post after this.

116 Views

Oops.

Well, here's what I've tried:

[bash]
vector::iterator b = primes.begin(), e = primes.end();
parallel_sort(b,e);
==============
parallel_sort(primes.begin(), primes.end());
==============
// I know this doesn't work
parallel_sort(primes.front(), primes.back());
==============
// I know this doesn't work
vector::iterator b = primes.begin(), e = primes.end();
int *be = &(*b), *en = &(*e);
parallel_sort(*be,*en);
==============
vector::iterator b = primes.begin(), e = primes.end();
parallel_sort(*b,*e);
==============
// Parallel qsort fail
parallel_for(0, 3, [=](int z) { qsort((void *)(primes.front() + z * ((primes.size())/4)), (primes.size())/4, sizeof(int), compare); }); parallel_for(0, 1, [=](int y) { qsort((void *)(primes.front() + y * ((primes.size())/2)), (primes.size())/2, sizeof(int), compare); }); qsort((void *)primes.front(), primes.size(), sizeof(int), compare); [/bash]

Thanks!

RafSchietekat
Black Belt
116 Views

What does "fail" mean: doesn't compile/link, wrong outcome, ...? Does anything change if you use tbb::parallel_sort instead of the parallel_sort by itself? front() and back() wouldn't work, nor would *begin() and *last(). I think I'll skip the parallel_for ones... Does "compare" provide "<" to qsort() or did you want something else? Have you tried the example in the Reference, and what happened?
ARCH_R_Intel
Employee
116 Views

You should be able to use tbb::parallel_sort just like std::sort as long as the operations on the type are thread-safe. Here's a transcript of a complete example on Linux.


[cpp]$ cat primes.cpp 
#include "tbb/tbb.h"
#include 
#include 

int main() {
    std::vector primes;
    primes.push_back(3);
    primes.push_back(7);
    primes.push_back(5);
    primes.push_back(2);
    tbb::parallel_sort( primes.begin(), primes.end() );
    for( size_t i=0; i << std::endl;
    return 0;
}
$ gcc primes.cpp -ltbb
$ a.out
2
3
5
7
[/cpp]
116 Views

Oops, it turned out that my cout was in the wrong place, thus outputting the wrong results. Thanks everyone!
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