Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

This is the documentation for a snapshot of the master branch, built from commit f8cf94d544.
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Function reduce

boost::compute::reduce

Synopsis

// In header: <boost/compute/algorithm/reduce.hpp>


template<typename InputIterator, typename OutputIterator, 
         typename BinaryFunction> 
  void reduce(InputIterator first, InputIterator last, OutputIterator result, 
              BinaryFunction function, 
              command_queue & queue = system::default_queue());
template<typename InputIterator, typename OutputIterator> 
  void reduce(InputIterator first, InputIterator last, OutputIterator result, 
              command_queue & queue = system::default_queue());

Description

Returns the result of applying function to the elements in the range [first, last).

If no function is specified, plus will be used.

The reduce() algorithm assumes that the binary reduction function is associative. When used with non-associative functions the result may be non-deterministic and vary in precision. Notably this affects the plus<float>() function as floating-point addition is not associative and may produce slightly different results than a serial algorithm.

This algorithm supports both host and device iterators for the result argument. This allows for values to be reduced and copied to the host all with a single function call.

For example, to calculate the sum of the values in a device vector and copy the result to a value on the host:


Note that while the the reduce() algorithm is conceptually identical to the accumulate() algorithm, its implementation is substantially more efficient on parallel hardware. For more information, see the documentation on the accumulate() algorithm.

Space complexity on GPUs: \Omega(n)
Space complexity on CPUs: \Omega(1)

See Also:

accumulate()

Parameters:

first

first element in the input range

function

binary reduction function

last

last element in the input range

queue

command queue to perform the operation

result

iterator pointing to the output


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