Deleted function compiler errors using thrust::remove in C++

Question

I am currently attempting to use the thrust::remove function on a thrust::device_vector of structs in my main function as shown bellow:

#include <iostream>
#include <thrust/device_vector.h>
#include <thrust/host_vector.h>
#include <thrust/execution_policy.h>
#include <thrust/remove.h>

struct config {
    unsigned int ld, ve, rd, solution;
    config() = default;
};

int main() {
    int n = 0;

    //initialize starting configuration
    int curr_size = 1, next_size;
    thrust::device_vector<config> curr(1);
    curr[1] = {0, 0, 0, 0};
    thrust::device_vector<config> next;
    thrust::device_vector<int> sums;

    for (int level = 0; level < ceil(n/2.0); ++level) {
         sums = thrust::device_vector<int>(curr_size);
         next = thrust::device_vector<config>(curr_size * n);
         thrust::fill(next.begin(), next.end(), config{0,0,0,0});



         next_size = thrust::reduce(thrust::device, sums.begin(), sums.end());
         //erroring code
         thrust::remove(thrust::device, curr.begin(), curr.end(), 0);
         next.resize(next_size);
         curr = thrust::device_vector<config>(next);
    }
}

however compiling the program leads to 9 compiler errors indicating invalid type conversions. I have attempted common fixes to thrust::remove errors such as running as a 64-bit project and even attempted it on a device_vector of ints but keep getting the same errors. Errors Shown Bellow(reduced due to character count limitations)

FAILED: CMakeFiles/Solver.dir/main.cu.o  
/usr/local/cuda-13.0/bin/nvcc -forward-unknown-to-host-compiler   -g "--generate-code=arch=compute_89,code=[compute_89,sm_89]" -MD -MT CMakeFiles/Solver.dir/main.cu.o -MF CMakeFiles/Solver.dir/main.cu.o.d -x cu -rdc=true -c /home/aowyn/CLionProjects/Solver/main.cu -o CMakeFiles/Solver.dir/main.cu.o
/usr/local/cuda-13.0/targets/x86_64-linux/include/cccl/cub/agent/agent_select_if.cuh(407): error: function "cuda::std::__4::__not_fn_t<_Fn>::operator()(_Args &&...) & [with _Fn=thrust::THRUST_300001_SM_890_NS::detail::functional::actor<thrust::THRUST_300001_SM_890_NS::detail::functional::composite<thrust::THRUST_300001_SM_890_NS::detail::functional::operator_adaptor<cuda::std::__4::equal_to<void>>, thrust::THRUST_300001_SM_890_NS::detail::functional::actor<thrust::THRUST_300001_SM_890_NS::detail::functional::argument<0U>>, thrust::THRUST_300001_SM_890_NS::detail::functional::actor<thrust::THRUST_300001_SM_890_NS::detail::functional::value<int>>>>, _Args=<config &>, __cccl_true_=true, <unnamed>=0]" (declared at line 62 of /usr/local/cuda-13.0/targets/x86_64-linux/include/cccl/cuda/std/__functional/not_fn.h) cannot be referenced -- it is a deleted function
          selection_flags[ITEM] = static_cast<bool>(select_op(items[ITEM]));

/usr/local/cuda-13.0/targets/x86_64-linux/include/cccl/cub/agent/agent_select_if.cuh(407): error: invalid type conversion
          selection_flags[ITEM] = static_cast<bool>(select_op(items[ITEM]));

/usr/local/cuda-13.0/targets/x86_64-linux/include/cccl/cub/agent/agent_select_if.cuh(407): error: function "cuda::std::__4::__not_fn_t<_Fn>::operator()(_Args &&...) & [with _Fn=thrust::THRUST_300001_SM_890_NS::detail::functional::actor<thrust::THRUST_300001_SM_890_NS::detail::functional::composite<thrust::THRUST_300001_SM_890_NS::detail::functional::operator_adaptor<cuda::std::__4::equal_to<void>>, thrust::THRUST_300001_SM_890_NS::detail::functional::actor<thrust::THRUST_300001_SM_890_NS::detail::functional::argument<0U>>, thrust::THRUST_300001_SM_890_NS::detail::functional::actor<thrust::THRUST_300001_SM_890_NS::detail::functional::value<int>>>>, _Args=<config &>, __cccl_true_=true, <unnamed>=0]" (declared at line 62 of /usr/local/cuda-13.0/targets/x86_64-linux/include/cccl/cuda/std/__functional/not_fn.h) cannot be referenced -- it is a deleted function
          selection_flags[ITEM] = static_cast<bool>(select_op(items[ITEM]));

/usr/local/cuda-13.0/targets/x86_64-linux/include/cccl/cub/agent/agent_select_if.cuh(407): error: invalid type conversion
          selection_flags[ITEM] = static_cast<bool>(select_op(items[ITEM]));

/usr/local/cuda-13.0/targets/x86_64-linux/include/cccl/cub/agent/agent_select_if.cuh(407): error: function "cuda::std::__4::__not_fn_t<_Fn>::operator()(_Args &&...) & [with _Fn=thrust::THRUST_300001_SM_890_NS::detail::functional::actor<thrust::THRUST_300001_SM_890_NS::detail::functional::composite<thrust::THRUST_300001_SM_890_NS::detail::functional::operator_adaptor<cuda::std::__4::equal_to<void>>, thrust::THRUST_300001_SM_890_NS::detail::functional::actor<thrust::THRUST_300001_SM_890_NS::detail::functional::argument<0U>>, thrust::THRUST_300001_SM_890_NS::detail::functional::actor<thrust::THRUST_300001_SM_890_NS::detail::functional::value<int>>>>, _Args=<config &>, __cccl_true_=true, <unnamed>=0]" (declared at line 62 of /usr/local/cuda-13.0/targets/x86_64-linux/include/cccl/cuda/std/__functional/not_fn.h) cannot be referenced -- it is a deleted function
          selection_flags[ITEM] = static_cast<bool>(select_op(items[ITEM]));

/usr/local/cuda-13.0/targets/x86_64-linux/include/cccl/cub/agent/agent_select_if.cuh(407): error: invalid type conversion
          selection_flags[ITEM] = static_cast<bool>(select_op(items[ITEM]));

/usr/local/cuda-13.0/targets/x86_64-linux/include/cccl/cub/agent/agent_select_if.cuh(407): error: function "cuda::std::__4::__not_fn_t<_Fn>::operator()(_Args &&...) & [with _Fn=thrust::THRUST_300001_SM_890_NS::detail::functional::actor<thrust::THRUST_300001_SM_890_NS::detail::functional::composite<thrust::THRUST_300001_SM_890_NS::detail::functional::operator_adaptor<cuda::std::__4::equal_to<void>>, thrust::THRUST_300001_SM_890_NS::detail::functional::actor<thrust::THRUST_300001_SM_890_NS::detail::functional::argument<0U>>, thrust::THRUST_300001_SM_890_NS::detail::functional::actor<thrust::THRUST_300001_SM_890_NS::detail::functional::value<int>>>>, _Args=<config &>, __cccl_true_=true, <unnamed>=0]" (declared at line 62 of /usr/local/cuda-13.0/targets/x86_64-linux/include/cccl/cuda/std/__functional/not_fn.h) cannot be referenced -- it is a deleted function
          selection_flags[ITEM] = static_cast<bool>(select_op(items[ITEM]));

/usr/local/cuda-13.0/targets/x86_64-linux/include/cccl/cub/agent/agent_select_if.cuh(407): error: invalid type conversion
          selection_flags[ITEM] = static_cast<bool>(select_op(items[ITEM]));

/usr/local/cuda-13.0/targets/x86_64-linux/include/cccl/thrust/detail/function.h(44): error: no instance of function template "thrust::THRUST_300001_SM_890_NS::detail::functional::actor<Eval>::operator() [with Eval=thrust::THRUST_300001_SM_890_NS::detail::functional::composite<thrust::THRUST_300001_SM_890_NS::detail::functional::operator_adaptor<cuda::std::__4::equal_to<void>>, thrust::THRUST_300001_SM_890_NS::detail::functional::actor<thrust::THRUST_300001_SM_890_NS::detail::functional::argument<0U>>, thrust::THRUST_300001_SM_890_NS::detail::functional::actor<thrust::THRUST_300001_SM_890_NS::detail::functional::value<int>>>]" matches the argument list
            argument types are: (config)
            object type is: thrust::THRUST_300001_SM_890_NS::detail::functional::actor<thrust::THRUST_300001_SM_890_NS::detail::functional::composite<thrust::THRUST_300001_SM_890_NS::detail::functional::operator_adaptor<cuda::std::__4::equal_to<void>>, thrust::THRUST_300001_SM_890_NS::detail::functional::actor<thrust::THRUST_300001_SM_890_NS::detail::functional::argument<0U>>, thrust::THRUST_300001_SM_890_NS::detail::functional::actor<thrust::THRUST_300001_SM_890_NS::detail::functional::value<int>>>>
      return static_cast<Result>(m_f(thrust::raw_reference_cast(::cuda::std::forward<Ts>(args))...));
                                 ^
/usr/local/cuda-13.0/targets/x86_64-linux/include/cccl/thrust/detail/functional/actor.h(59): note #3327-D: candidate function template "thrust::THRUST_300001_SM_890_NS::detail::functional::actor<Eval>::operator() [with Eval=thrust::THRUST_300001_SM_890_NS::detail::functional::composite<thrust::THRUST_300001_SM_890_NS::detail::functional::operator_adaptor<cuda::std::__4::equal_to<void>>, thrust::THRUST_300001_SM_890_NS::detail::functional::actor<thrust::THRUST_300001_SM_890_NS::detail::functional::argument<0U>>, thrust::THRUST_300001_SM_890_NS::detail::functional::actor<thrust::THRUST_300001_SM_890_NS::detail::functional::value<int>>>]" failed deduction
                     auto operator()(Ts&&... ts) const -> decltype(Eval::eval(::cuda::std::forward<decltype(ts)>(ts)...))

9 errors detected in the compilation of "/home/aowyn/CLionProjects/Solver/main.cu".
ninja: build stopped: subcommand failed.

Any suggestions on how to fix this would be greatly appreciated, thank you.

curr[1] = {0, 0, 0, 0}; is an off-by-one error. Given that vector elements (i.e. curr[0]) are already default constructed, the whole access is unnecessary. Same goes for the fill. — paleonix
– paleonix, Commented Nov 11 at 17:22
While some critical information about the actual code was probably lost when creating the MRE, the usage of vector-constructors in the loop seems very inefficient to me. Allocation of device memory is not cheap. I suggest working more with either views (cuda::std::span is backported to C++17), swap()/move() or resize() (it is unclear if sizes are going up or down in later iterations). — paleonix
– paleonix, Commented Nov 11 at 17:32

pptaszni · Accepted Answer · 2025-11-11 14:40:46Z

5

Signature of remove is

template<typename DerivedPolicy, typename ForwardIterator, typename T>
ForwardIterator thrust::remove(
const thrust::detail::execution_policy_base<DerivedPolicy> &exec,
ForwardIterator first,
ForwardIterator last,
const T &value,
)

The last argument should be of type T (or something implicitly convertible to T), but you used 0. If you mean to remove the config element that is {0, 0, 0, 0}, the quick fix could be:

struct config {
    unsigned int ld, ve, rd, solution;
    // default possible since c++20, otherwise you need to implement it
    bool operator==(const config&) const = default;
};

and then

thrust::remove(thrust::device, curr.begin(), curr.end(), config{0, 0, 0, 0});

Note the defaulted comparison operator. You don't need to explicitly declare default constructor.

edited Nov 11 at 14:40

answered Nov 11 at 10:13

pptaszni

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2 Comments

AowynB Nov 11 at 14:20

Thank you very much! notably when i used the suggested line my I got an error saying that the extra = default is not supported in my language dialect. but once i removed it and just used bool operator==(const config&) const; it compiled fine.

pptaszni Nov 11 at 14:39

A yes, forgot to mention that defaulted comparison operators are supported since C++20 en.cppreference.com/w/cpp/language/default_comparisons.html

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