I am using tiled_range with a sort_by_key() in cuda and the keys are not getting re-ordered during the sort_by_key, just the values...
For example: I have one vector representing the keys:
Keys 0 1 2 3 4 5
Later with the tiled_range, I have the new vector with the values duplicated.
Keys 0 1 2 3 4 5 0 1 2 3 4 5
And another vector representing the values:
values 0 3382 1863 470 311 2017 3382 0 251 1394 5651 257
I was expecting with sort_by_keys to re-order the keys like this:
Keys 0 0 1 1 2 2 3 3 4 4 5 5
Values 0 3382 3382 0 1863 251 470 1394 311 5651 2017 257
My code re-orders the keys in this way...
Keys 3 3 4 4 5 5 3 3 4 4 5 5
Values 0 3382 3382 0 1863 251 470 1394 311 5651 2017 257
I was wondering, what could be the reason is re-ordering in this way and what can I do to get the right order?
Here is the code:
#include <iterator>
#include <thrust/device_vector.h>
#include <thrust/host_vector.h>
#include <thrust/sort.h>
using namespace thrust::placeholders;
template<typename Iterator>
class tiled_range
//Code of tiled_range....
//
int main(void)
{
thrust::device_vector<int> data(6);
data[0] = 0; data[1] = 1; data[2] = 2; data[3] = 3; data[4] = 4; data[5] = 5;
thrust::device_vector<float> values(12);
values[0] = 0; values[6] = 3382;
values[1] = 3382; values[7] = 0;
values[2] = 1863; values[8] = 251;
values[3] = 470; values[9] = 1394;
values[4] = 311; values[10] = 5651;
values[5] = 2017; values[11] = 257;
tiled_range<thrust::device_vector<int>::iterator> keys(data.begin(), data.end(), 2);
std::cout << "Keys: " << std::endl;
thrust::copy(keys.begin(), keys.end(), std::ostream_iterator<int>(std::cout, " "));
std::cout << std::endl;
thrust::sort_by_key(keys.begin(), keys.end(), values.begin());
std::cout << "Keys: " << std::endl;
thrust::copy(keys.begin(), keys.end(), std::ostream_iterator<int>(std::cout, " "));
std::cout << std::endl;
std::cout << "Values: " << std::endl;
thrust::copy(values.begin(), values.end(), std::ostream_iterator<int> (std::cout, " "));
std::cout << std::endl;
return 0;
}
Problem solved! I was checking some code from: https://groups.google.com/forum/#!msg/thrust-users/GqufHKoaizc/qx9cv-6xCg4J
and I noticed that they were copy the values of the tiled_range into another vector, after copying this new vector and put it in the sort_by_keys, it was sorting the keys and values perfectly. I still do not understand why by putting the iterator of the tiled_range as input for the sort_by_keys it was causing such mess above...
Here is the code:
#include <iterator>
#include <thrust/device_vector.h>
#include <thrust/host_vector.h>
#include <thrust/sort.h>
using namespace thrust::placeholders;
template<typename Iterator>
class tiled_range
//Code of tiled_range....
//
int main(void)
{
thrust::device_vector<int> data(6);
data[0] = 0; data[1] = 1; data[2] = 2; data[3] = 3; data[4] = 4; data[5] = 5;
thrust::device_vector<float> values(12);
values[0] = 0; values[6] = 3382;
values[1] = 3382; values[7] = 0;
values[2] = 1863; values[8] = 251;
values[3] = 470; values[9] = 1394;
values[4] = 311; values[10] = 5651;
values[5] = 2017; values[11] = 257;
tiled_range<thrust::device_vector<int>::iterator> keys(data.begin(), data.end(), 2);
thrust::device_vector<int> keysN(keys.begin(), keys.end());
std::cout << "Keys: " << std::endl;
thrust::copy(keysN.begin(), keysN.end(), std::ostream_iterator<int>(std::cout, " "));
std::cout << std::endl;
thrust::sort_by_key(keysN.begin(), keysN.end(), values.begin());
std::cout << "Keys: " << std::endl;
thrust::copy(keys.begin(), keys.end(), std::ostream_iterator<int>(std::cout, " "));
std::cout << std::endl;
std::cout << "Values: " << std::endl;
thrust::copy(values.begin(), values.end(), std::ostream_iterator<int> (std::cout, " "));
std::cout << std::endl;
return 0;
}