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pbbslib

Contains the PBBS (Problem Based Benchmark Suite) library. This is a collection of parallel algorithms and other support for parallelism written in C++. It supports a reasonably wide variety of algorithms that run on shared memory multicores. In addition to the algorithms it supports a parallel scheduleer and a memory allocator. It only needs the c++ standard threads utilities.

The library encourages a more functional style of programming than the algorithms available in the standard template library. It borrows some ideas from Boost.

PBBS includes:

  • a library of algorithms, mostly based on sequences and ranges
  • a scheduler (based on arbitrarily nested fork-join parallelism)
  • a memory allocator (optimized for parallelism)
  • parallel random number generation

Algorithms (all parallel):

  • reduce, scan, scan_inplace
  • pack, filter, pack_index
  • merge
  • random_shuffle
  • histogram
  • integer_sort, counting_sort, sort, sort_inplace, stable_sort
  • collect_reduce
  • kth_smallest

It also includes the following, which are loosely based on the standard template library. However none of them mutate their arguments, but rather are copy based.

  • all_of, any_of, none_of, count, count_if
  • find, find_if, find_if_not, find_first_of, find_end, search
  • mismatch, adjacent_find
  • equal, lexicographical_compare,
  • unique, remove_if
  • min_element, max_element, min_max_element
  • reverse, rotate,
  • is_sorted, is_sorted_until, is_partitioned

Utilities

  • scheduler
  • parallel random number generator
  • memory allocator
  • monoid
  • timer
  • hashing

Concurrency

  • stack

Seqs and Ranges

Much of The library revolves around the concepts of Seq and Range.

Seq

A Seq is a type supporting at least a.size(), a.split(), a.split(start,end) and and a[i], where the last can return an rval. The split functions return a Seq (possibly also a Range). It must also contain a value_type. No iterator needs to be associated with a Seq. A general Seq cannot be mutated (none of its functionality supports mutation). Functions that take a Seq as an argument almost always take it as a const reference.

Range

A Range can be thought of as a pair of iterators marking the start and end of the range. It must support all the operations of Seq (it is also a Seq), and in addition, it must also support a.begin(), a.end() and must have a type iterator. Importantly Range's should not have any memory associated with them for their underlining container. They are meant to reference a range (perhaps the full range) of an underlining container. This is different from the concept of Range in boost.

sequence, range and delayed_sequence

The library supports three specific types of Seq and Range.

sequence

A sequence is similar to a vector in that it is associated with the underlying memory for its contents. Unlike vector it is generally meant to be immutable, although it does support mutation by first extracting a range. It is designed so all its internal operations are parallel---including initialization of elements, destruction of elements, copy assignment and copy construction. It supports the following functionality:

typename value_type (shorthand T below)
sequence<T>(size_t n, IntegerFunc f) :
    applies f to i : [0,n) creating a sequence of length n
sequence<T>() : creates a zero length sequence
sequence<T>(size_t n) : creates a sequence of length n
sequence<T>(size_t n, T v) :
    creates an sequence of length n initializing with v
sequence<T>(Range r) :
    creates a sequence from the range r
a.size() -> size_t : size of a
a.slice() -> range<T*> : a Range encompasing full range of a
a.slice(size_t s, size_t e) -> range<T*> :
    a Range encompasing [s,e) of a.
a.begin() : shorthand for a.slice().begin()
a.end() : shorthand for a.slice().end()
a[size_t i] -> T& : reference to i-th value of a
a.swap(sequence<T> b) -> void : swaps contents of a and b
a.clear() -> clears the contents setting length to zero.

If passed by rvalue reference it is moved clearing the rvalue. If passed by value, it is copied.

A sequence is a Seq but not a Range.

range

A range suppors random access into range, and slicing into subranges.

typename value_type (shorthand T below)
typename iterator, where iterator::value_type = value_type
   it must be a random access iterator
range<I>(I begin, I end) : the range from begin to end
a.size() -> size_t : size of the range
a.slice() -> range<I> : returns a 
a.slice(size_t s, size_t e) -> range<I> :
    the subrange from a.begin()+s to a.begin()+e, 
a.begin() -> I : an iterator to the begining of the range
a.end() -> I : an iterator to the end of the range
a[size_t i] -> value_type& : reference to i-th value of a

A range is both a Seq and a Range.

delayed_sequence<T, IntegerFunc>

A delayed_sequence<T, IntegerFunc> is associated with a function that emits the i-th element. It is hence immutable, and there is no notion of a reference to its elements. It supports:

typename value_type (shorthand T below)
delayed_sequence(size_t n, IntegerFunc f) :
  creates a delayed sequence of length n, where the i-th element is f(i)
  the function is applied on demand, not when the delayed sequence is created
delayed_sequence(size_t n, T v) :
  the function is the constant function returning v for every i
a[size_t i] -> value_type : f(i)
a.slice() -> delayed_sequence<T, IntegerFunc> : a
a.slice(size_t s, size_t e) -> delayed_sequence<T, IntegerFunc> :
    the range from [f(s), f(e))

A delayed_sequence is a Seq but not a Range