Insert into host_vector using thrust

Question

I'm trying to insert one value into the third location in a host_vector using thrust.

static thrust::host_vector <int *> bins; int * p; bins.insert(3, 1, p);

But am getting errors:

error: no instance of overloaded function "thrust::host_vector<T, Alloc>::insert [with T=int *, Alloc=std::allocator<int *>]" matches the argument list argument types are: (int, int, int *) object type is: thrust::host_vector<int *, std::allocator<int *>>

Has anyone seen this before, and how can I solve this? I want to use a vector to pass information into the GPU. I was originally trying to use a vector of vectors to represent spatial cells that hold different numbers of data, but learned that wasn't possible with thrust. So instead, I'm using a vector bins that holds my data, sorted by the spatial cell (first 3 values might correspond to the first cell, the next 2 to the second cell, the next 0 to the third cell, etc.). The values held are pointers to particles, and represent the numbers of particles in the spatial cell (which is not known before runtime).

Your code doesn't work if you replace thrust::host_vector with std::vector, so I'm not sure why you think it would work with thrust. The first argument is supposed to be an iterator. So if you change bins.insert(3,1,p); to bins.insert(bins.begin()+3, 1, p); I think it should compile for you. You might want to study the standard vector insert documentation. — Robert Crovella
As an aside, I think you're going to find a vector of pointers rather difficult to work with, but that is not the question you are asking. Rather than a vector of pointers to particles, just use a vector of particles, would be my advice. — Robert Crovella

Unknown Unknown · Accepted Answer · 2017-03-07T10:06:10

As noted in comments, thrust::host_vector is modelled directly on std::vector and the operation you are trying to use requires an iterator for the position argument, which is why you get a compilation error. You can see this if you consult the relevant documentation:

http://en.cppreference.com/w/cpp/container/vector/insert https://thrust.github.io/doc/classthrust_1_1host__vector.html#a9bb7c8e26ee8c10c5721b584081ae065

A complete working example of the code snippet you showed would look like this:

#include <iostream>
#include <thrust/host_vector.h>

int main()
{
    thrust::host_vector <int *> bins(10, reinterpret_cast<int *>(0));
    int * p = reinterpret_cast<int *>(0xdeadbeef);
    bins.insert(bins.begin()+3, 1, p);

    auto it = bins.begin();
    for(int i=0; it != bins.end(); ++it, i++) {
        int* v = *it;
        std::cout << i << " " << v << std::endl;
    }
    return 0;
}

Note that this requires that C++11 language features are enabled in nvcc (so use CUDA 8.0):

~/SO$ nvcc -std=c++11 -arch=sm_52 thrust_insert.cu 
~/SO$ ./a.out 
0 0
1 0
2 0
3 0xdeadbeef
4 0
5 0
6 0
7 0
8 0
9 0
10 0

Insert into host_vector using thrust

1 Answers