[Bug] thrust::reduce_by_key triggers compilation error on thrust 1.17.2

[lilohuang]

Hi @senior-zero and @allisonvacanti ,

Using CUDA 11.8 compiler to compile below example code with thrust 1.17.2 and cub 1.17.2 produces compilation error. There is no error on thrust 1.16 with cub 1.16.

I suspect this could be a new bug introduced by #1671 code change in thrust 1.17 but didn't get a chance to triangulate the root cause.

#include <cstdint>
#include <thrust/execution_policy.h>
#include <thrust/reduce.h>
#include <thrust/device_vector.h>
#include <thrust/iterator/discard_iterator.h>
#include <thrust/iterator/transform_output_iterator.h>

int main() {

   thrust::device_vector<int32_t> key(16);
   thrust::device_vector<int32_t> value(16);

   thrust::reduce_by_key(thrust::device, key.begin(), key.end(),
      value.begin(),
      thrust::make_discard_iterator(),
      thrust::make_transform_output_iterator(
         thrust::make_discard_iterator(),
         thrust::negate<int32_t>()));

   return 0;
}

no instance of constructor "thrust::transform_output_iterator<UnaryFunction, OutputIterator>::transform_output_iterator [with UnaryFunction=thrust::negate<int32_t>, OutputIterator=thrust::discard_iterator<thrust::use_default>]" matches the argument list

Please let me know if you cannot reproduce the bug.

Thanks,
Lilo

[gevtushenko]

@lilohuang thank you for reporting this! I can reproduce the issue. Could you please verify the following fix?

[lilohuang]

@senior-zero thanks for your quick fix. No compilation error after applying #1827 fix. Please close this issue once it's merged.