stxxl::generate

Author

Roman Dementiev (2006)

The semantics of the algorithm are equivalent to the STL std::generate.

Prototype

template < typename ExtIterator, typename Generator >
void generate ( ExtIterator first,
                ExtIterator last,
                Generator   generator,
                int_type    nbuffers
              )

Description

Generate assigns the result of invoking generator, a function object that takes no arguments, to each element in the range [first, last). To overlap I/O and computation nbuffers are used (a value at least D is recommended). The size of the buffers is derived from the container that is pointed by the iterators.

Remarks

The implementation exploits STXXL buffered streams (computation and I/O overlapped).

Parameters

begin	object of model of ext_random_access_iterator concept
end	object of model of ext_random_access_iterator concept
generator	function object of model of std::generator concept
nbuffers	number of buffers (blocks) for internal use (should be at least 2*D, or zero for automaticl 2*D)

Requirements on types

• ExtIterator is a model of External Random Access Iterator.
• ExtIterator is mutable.
• Generator is a model of a STL Generator.
• Generator's result type is convertible to ExtIterator's value type.

Preconditions

[first, last) is a valid range.

Complexity

• Internal work is linear.
• External work: close to I/Os (write-only).

Example

// Fill a vector with random numbers, using the
// standard C library function rand.
typedef stxxl::VECTOR_GENERATOR<int>::result vector_type;
vector_type V(some_size);
// use 20 buffer blocks
stxxl::generate(V.begin(), V.end(), rand, 20);