# CUDA Standard Algorithms » Single Task

Taskflow provides a standard template method for running a callable using a single GPU thread.

## Include the Header

You need to include the header file, `taskflow/cuda/algorithm/for_each.hpp`, for creating a single-threaded task.

    #include <taskflow/cuda/algorithm/for_each.hpp>

## Run a Task with a Single Thread

You can launch a kernel with only one GPU thread running it, which is handy when you want to set up a single or a few variables that do not need multiple threads. The following example creates a single-task kernel that sets a device variable to `1`.

    tf::cudaStream stream;
    tf::cudaDefaultExecutionPolicy policy(stream);

    // launch the single-task kernel asynchronously through the policy
    tf::cuda_single_task(policy, [gpu_variable] __device__ () {
      *gpu_Variable = 1;
    });

    // wait for the kernel completes
    stream.synchronize();

Since the callable runs on GPU, it must be declared with a `__device__` specifier.

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