Template Function thrust::inclusive_scan(InputIterator, InputIterator, OutputIterator, AssociativeOperator)

Function Documentation

template<typename InputIterator, typename OutputIterator, typename AssociativeOperator>
OutputIterator thrust::inclusive_scan(InputIterator first, InputIterator last, OutputIterator result, AssociativeOperator binary_op)

inclusive_scan computes an inclusive prefix sum operation. The term ‘inclusive’ means that each result includes the corresponding input operand in the partial sum. When the input and output sequences are the same, the scan is performed in-place.

inclusive_scan is similar to std::partial_sum in the STL. The primary difference between the two functions is that std::partial_sum guarantees a serial summation order, while inclusive_scan requires associativity of the binary operation to parallelize the prefix sum.

The following code snippet demonstrates how to use

inclusive_scan
Return

The end of the output sequence.

Pre

first may equal result but the range [first, last) and the range [result, result + (last - first)) shall not overlap otherwise.

Parameters

  • first: The beginning of the input sequence.

  • last: The end of the input sequence.

  • result: The beginning of the output sequence.

  • binary_op: The associatve operator used to ‘sum’ values.

Template Parameters

  • InputIterator: is a model of Input Iterator and InputIterator's value_type is convertible to OutputIterator's value_type.

  • OutputIterator: is a model of Output Iterator and OutputIterator's value_type is convertible to both AssociativeOperator's first_argument_type and second_argument_type.

  • AssociativeOperator: is a model of Binary Function and AssociativeOperator's result_type is convertible to OutputIterator's value_type.

int data[10] = {-5, 0, 2, -3, 2, 4, 0, -1, 2, 8};

thrust::maximum<int> binary_op;

thrust::inclusive_scan(data, data + 10, data, binary_op); // in-place scan

// data is now {-5, 0, 2, 2, 2, 4, 4, 4, 4, 8}

See

http://www.sgi.com/tech/stl/partial_sum.html