How do I reorder a vector during a Thrust transformation?
How could i transform this simple code to thrust code?
for (i=0;i<cA-rA;i++)
sn[i]=c[n_index[i]]-sn[i];
More Info: cA and rA are const integers so we can concider as an 'n'= cA-rA sn : array of float(n) n_index : array of int(n) c : array of float(cA)
My开发者_Go百科 problem is with the n_index[i] that points to the element of the C array. thank you!
You can implement this by fusing thrust::transform
with a "gather" operation using a permutation_iterator
:
#include <thrust/device_vector.h>
#include <thrust/iterator/permutation_iterator.h>
#include <thrust/transform.h>
#include <thrust/sequence.h>
#include <thrust/functional.h>
int main()
{
size_t n = 100;
// declare storage
thrust::device_vector<int> sn(n);
thrust::device_vector<int> n_index(n);
thrust::device_vector<int> c(n);
// initialize vectors with some sequential values for demonstrative purposes
thrust::sequence(sn.begin(), sn.end());
thrust::sequence(n_index.begin(), n_index.end());
thrust::sequence(c.begin(), c.end());
// sn[i] = c[n_index[i]] - sn[i]
thrust::transform(thrust::make_permutation_iterator(c.begin(), n_index.begin()),
thrust::make_permutation_iterator(c.end(), n_index.end()),
sn.begin(),
sn.begin(),
thrust::minus<int>());
return 0;
}
I tried the first one and wasn't getting the correct results. the second permutation_iterator needs to be at the end of BOTH vectors.
Try the following correction:
// sn[i] = c[n_index[i]] - sn[i] thrust::transform(thrust::make_permutation_iterator(c.begin(), n_index.begin()), thrust::make_permutation_iterator(c.end(), n_index.end()), sn.begin(), sn.begin(), thrust::minus<int>());
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