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openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize > Class Template Reference

Concurrent, page-based, dynamically-sized linear data structure with O(1) random access and STL-compliant iterators. It is primarily intended for applications that concurrently insert (a possibly unkown number of) elements into a dynamically growing linear array, and fast random access to said elements. More...

#include <PagedArray.h>

Classes

class  ConstIterator
 
class  Iterator
 
class  Page
 
class  ValueBuffer
 

Public Types

using ValueType = ValueT
 
using Ptr = SharedPtr< PagedArray >
 

Public Member Functions

 PagedArray ()
 Default constructor. More...
 
 ~PagedArray ()
 Destructor removed all allocated pages. More...
 
 PagedArray (const PagedArray &)=delete
 
PagedArray & operator= (const PagedArray &)=delete
 
ValueBuffer getBuffer ()
 
size_t push_back_unsafe (const ValueType &value)
 
void shrink_to_fit ()
 Reduce the page table to fix the current size. More...
 
ValueType & operator[] (size_t i)
 Return a reference to the value at the specified offset. More...
 
const ValueType & operator[] (size_t i) const
 Return a const-reference to the value at the specified offset. More...
 
void fill (const ValueType &v)
 Set all elements in the page table to the specified value. More...
 
bool copy (ValueType *p, size_t count) const
 Copy the first count values in this PageArray into a raw c-style array, assuming it to be at least count elements long. More...
 
void copy (ValueType *p) const
 
void resize (size_t size)
 Resize this array to the specified size. More...
 
void resize (size_t size, const ValueType &v)
 Resize this array to the specified size and initialize all values to v. More...
 
size_t size () const
 Return the number of elements in this array. More...
 
size_t capacity () const
 Return the maximum number of elements that this array can contain without allocating more memory pages. More...
 
size_t freeCount () const
 Return the number of additional elements that can be added to this array without allocating more memory pages. More...
 
size_t pageCount () const
 Return the number of allocated memory pages. More...
 
size_t memUsage () const
 Return the memory footprint of this array in bytes. More...
 
bool isEmpty () const
 Return true if the container contains no elements. More...
 
bool isPartiallyFull () const
 Return true if the page table is partially full, i.e. the last non-empty page contains less than pageSize() elements. More...
 
void clear ()
 Removes all elements from the array and delete all pages. More...
 
Iterator begin ()
 Return a non-const iterator pointing to the first element. More...
 
Iterator end ()
 Return a non-const iterator pointing to the past-the-last element. More...
 
void sort ()
 Parallel sort of all the elements in ascending order. More...
 
void invSort ()
 Parallel sort of all the elements in descending order. More...
 
void merge (PagedArray &other)
 Transfer all the elements (and pages) from the other array to this array. More...
 
void print (std::ostream &os=std::cout) const
 Print information for debugging. More...
 
ConstIterator cbegin () const
 Return a const iterator pointing to the first element. More...
 
ConstIterator begin () const
 Return a const iterator pointing to the first element. More...
 
ConstIterator cend () const
 Return a const iterator pointing to the past-the-last element. More...
 
ConstIterator end () const
 Return a const iterator pointing to the past-the-last element. More...
 
template<typename Functor >
void sort (Functor func)
 Parallel sort of all the elements based on a custom functor with the api: More...
 

Static Public Member Functions

static Ptr create ()
 Return a shared pointer to a new instance of this class. More...
 
static size_t pageSize ()
 Return the number of elements per memory page. More...
 
static size_t log2PageSize ()
 Return log2 of the number of elements per memory page. More...
 

Friends

class ValueBuffer
 

Detailed Description

template<typename ValueT, size_t Log2PageSize = 10UL>
class openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >

Concurrent, page-based, dynamically-sized linear data structure with O(1) random access and STL-compliant iterators. It is primarily intended for applications that concurrently insert (a possibly unkown number of) elements into a dynamically growing linear array, and fast random access to said elements.

Note
Multiple threads can grow the page-table and push_back new elements concurrently. A ValueBuffer provides accelerated and threadsafe push_back at the cost of potentially re-ordering elements (when multiple instances are used).

This data structure employes contiguous pages of elements (a std::deque) which avoids moving data when the capacity is out-grown and new pages are allocated. The size of the pages can be controlled with the Log2PageSize template parameter (defaults to 1024 elements of type ValueT).

There are three fundamentally different ways to insert elements to this container - each with different advanteges and disadvanteges.

The simplest way to insert elements is to use PagedArray::push_back_unsafe which is not thread-safe:

PagedArray<size_t> array;
for (size_t i=0; i<100000; ++i) array.push_back_unsafe(i);

The fastest way (by far) to insert elements is by means of a PagedArray::ValueBuffer:

PagedArray<size_t> array;
auto buffer = array.getBuffer();
for (size_t i=0; i<100000; ++i) buffer.push_back(i);
buffer.flush();

or

PagedArray<size_t> array;
{
//local scope of a single thread
auto buffer = array.getBuffer();
for (size_t i=0; i<100000; ++i) buffer.push_back(i);
}

or with TBB task-based multi-threading:

PagedArray<size_t> array;
tbb::parallel_for(
tbb::blocked_range<size_t>(0, 10000, array.pageSize()),
[&array](const tbb::blocked_range<size_t>& range) {
auto buffer = array.getBuffer();
for (size_t i=range.begin(); i!=range.end(); ++i) buffer.push_back(i);
}
);

or with TBB thread-local storage for even better performance (due to fewer concurrent instantiations of partially full ValueBuffers)

PagedArray<size_t> array;
auto exemplar = array.getBuffer();//dummy used for initialization
tbb::enumerable_thread_specific<PagedArray<size_t>::ValueBuffer>
pool(exemplar);//thread local storage pool of ValueBuffers
tbb::parallel_for(
tbb::blocked_range<size_t>(0, 10000, array.pageSize()),
[&pool](const tbb::blocked_range<size_t>& range) {
auto &buffer = pool.local();
for (size_t i=range.begin(); i!=range.end(); ++i) buffer.push_back(i);
}
);
for (auto i=pool.begin(); i!=pool.end(); ++i) i->flush();

This technique generally outperforms PagedArray::push_back_unsafe, std::vector::push_back, std::deque::push_back and even tbb::concurrent_vector::push_back. Additionally it is thread-safe as long as each thread has it's own instance of a PagedArray::ValueBuffer. The only disadvantage is the ordering of the elements is undefined if multiple instance of a PagedArray::ValueBuffer are employed. This is typically the case in the context of multi-threading, where the ordering of inserts are undefined anyway. Note that a local scope can be used to guarentee that the ValueBuffer has inserted all its elements by the time the scope ends. Alternatively the ValueBuffer can be explicitly flushed by calling ValueBuffer::flush.

The third way to insert elements is to resize the container and use random access, e.g.

PagedArray<int> array;
array.resize(100000);
for (int i=0; i<100000; ++i) array[i] = i;

or in terms of the random access iterator

PagedArray<int> array;
array.resize(100000);
for (auto i=array.begin(); i!=array.end(); ++i) *i = i.pos();

While this approach is both fast and thread-safe it suffers from the major disadvantage that the problem size, i.e. number of elements, needs to be known in advance. If that's the case you might as well consider using std::vector or a raw c-style array! In other words the PagedArray is most useful in the context of applications that involve multi-threading of dynamically growing linear arrays that require fast random access.

Definition at line 143 of file PagedArray.h.

Member Typedef Documentation

template<typename ValueT , size_t Log2PageSize = 10UL>
using openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::Ptr = SharedPtr<PagedArray>

Definition at line 154 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
using openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::ValueType = ValueT

Definition at line 153 of file PagedArray.h.

Constructor & Destructor Documentation

template<typename ValueT , size_t Log2PageSize = 10UL>
openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::PagedArray ( )
inline

Default constructor.

Definition at line 157 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::~PagedArray ( )
inline

Destructor removed all allocated pages.

Definition at line 160 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::PagedArray ( const PagedArray< ValueT, Log2PageSize > &  )
delete

Member Function Documentation

template<typename ValueT , size_t Log2PageSize = 10UL>
Iterator openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::begin ( void  )
inline

Return a non-const iterator pointing to the first element.

Definition at line 368 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
ConstIterator openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::begin ( void  ) const
inline

Return a const iterator pointing to the first element.

Definition at line 380 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
size_t openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::capacity ( ) const
inline

Return the maximum number of elements that this array can contain without allocating more memory pages.

Definition at line 324 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
ConstIterator openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::cbegin ( ) const
inline

Return a const iterator pointing to the first element.

Definition at line 379 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
ConstIterator openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::cend ( ) const
inline

Return a const iterator pointing to the past-the-last element.

Warning
Iterator does not point to a valid element and should not be dereferenced!

Definition at line 389 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
void openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::clear ( void  )
inline

Removes all elements from the array and delete all pages.

Warning
Not thread-safe!

Definition at line 359 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
bool openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::copy ( ValueType *  p,
size_t  count 
) const
inline

Copy the first count values in this PageArray into a raw c-style array, assuming it to be at least count elements long.

Parameters
ppointer to an array that will used as the destination of the copy.
countnumber of elements to be copied.

Definition at line 255 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
void openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::copy ( ValueType *  p) const
inline

Definition at line 272 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
static Ptr openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::create ( )
inlinestatic

Return a shared pointer to a new instance of this class.

Definition at line 167 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
Iterator openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::end ( void  )
inline

Return a non-const iterator pointing to the past-the-last element.

Warning
Iterator does not point to a valid element and should not be dereferenced!

Definition at line 375 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
ConstIterator openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::end ( void  ) const
inline

Return a const iterator pointing to the past-the-last element.

Warning
Iterator does not point to a valid element and should not be dereferenced!

Definition at line 390 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
void openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::fill ( const ValueType &  v)
inline

Set all elements in the page table to the specified value.

Parameters
vvalue to be filled in all the existing pages of this PagedArray.
Note
Multi-threaded

Definition at line 240 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
size_t openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::freeCount ( ) const
inline

Return the number of additional elements that can be added to this array without allocating more memory pages.

Definition at line 328 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
ValueBuffer openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::getBuffer ( )
inline
Returns
a new instance of a ValueBuffer which supports thread-safe push_back!

Definition at line 180 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
void openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::invSort ( )
inline

Parallel sort of all the elements in descending order.

Definition at line 397 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
bool openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::isEmpty ( ) const
inline

Return true if the container contains no elements.

Definition at line 346 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
bool openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::isPartiallyFull ( ) const
inline

Return true if the page table is partially full, i.e. the last non-empty page contains less than pageSize() elements.

When the page table is partially full calling merge() or using a ValueBuffer will rearrange the ordering of existing elements.

Definition at line 354 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
static size_t openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::log2PageSize ( )
inlinestatic

Return log2 of the number of elements per memory page.

Definition at line 337 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
size_t openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::memUsage ( ) const
inline

Return the memory footprint of this array in bytes.

Definition at line 340 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize>
void openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::merge ( PagedArray< ValueT, Log2PageSize > &  other)

Transfer all the elements (and pages) from the other array to this array.

Parameters
othernon-const reference to the PagedArray that will be merged into this PagedArray.
Note
The other PagedArray is empty on return.
Warning
The ordering of elements is undefined if this page table is partially full!

Definition at line 476 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
PagedArray& openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::operator= ( const PagedArray< ValueT, Log2PageSize > &  )
delete
template<typename ValueT , size_t Log2PageSize = 10UL>
ValueType& openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::operator[] ( size_t  i)
inline

Return a reference to the value at the specified offset.

Parameters
ilinear offset of the value to be accessed.
Note
This random access has constant time complexity.
Warning
It is assumed that the i'th element is already allocated!

Definition at line 216 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
const ValueType& openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::operator[] ( size_t  i) const
inline

Return a const-reference to the value at the specified offset.

Parameters
ilinear offset of the value to be accessed.
Note
This random access has constant time complexity.
Warning
It is assumed that the i'th element is already allocated!

Definition at line 229 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
size_t openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::pageCount ( ) const
inline

Return the number of allocated memory pages.

Definition at line 331 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
static size_t openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::pageSize ( )
inlinestatic

Return the number of elements per memory page.

Definition at line 334 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
void openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::print ( std::ostream &  os = std::cout) const
inline

Print information for debugging.

Definition at line 418 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
size_t openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::push_back_unsafe ( const ValueType &  value)
inline
Parameters
valuevalue to be added to this PagedArray
Note
For best performance consider using the ValueBuffer!
Warning
Not thread-safe and mostly intended for debugging!

Definition at line 193 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
void openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::resize ( size_t  size)
inline

Resize this array to the specified size.

Parameters
sizenumber of elements that this PageArray will contain.

Will grow or shrink the page table to contain the specified number of elements. It will affect the size(), iteration will go over all those elements, push_back will insert after them and operator[] can be used directly access them.

Note
No reserve method is implemented due to efficiency concerns (especially for the ValueBuffer) from having to deal with empty pages.
Warning
Not thread-safe!

Definition at line 288 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
void openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::resize ( size_t  size,
const ValueType &  v 
)
inline

Resize this array to the specified size and initialize all values to v.

Parameters
sizenumber of elements that this PageArray will contain.
vvalue of all the size values.

Will grow or shrink the page table to contain the specified number of elements. It will affect the size(), iteration will go over all those elements, push_back will insert after them and operator[] can be used directly access them.

Note
No reserve method is implemented due to efficiency concerns (especially for the ValueBuffer) from having to deal with empty pages.
Warning
Not thread-safe!

Definition at line 313 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize>
void openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::shrink_to_fit ( )

Reduce the page table to fix the current size.

Warning
Not thread-safe!

Definition at line 462 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
size_t openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::size ( void  ) const
inline

Return the number of elements in this array.

Definition at line 320 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
void openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::sort ( )
inline

Parallel sort of all the elements in ascending order.

Definition at line 394 of file PagedArray.h.

template<typename ValueT , size_t Log2PageSize = 10UL>
template<typename Functor >
void openvdb::OPENVDB_VERSION_NAME::util::PagedArray< ValueT, Log2PageSize >::sort ( Functor  func)
inline

Parallel sort of all the elements based on a custom functor with the api:

bool operator()(const ValueT& a, const ValueT& b)

which returns true if a comes before b.

Definition at line 405 of file PagedArray.h.

Friends And Related Function Documentation

template<typename ValueT , size_t Log2PageSize = 10UL>
friend class ValueBuffer
friend

Definition at line 430 of file PagedArray.h.

The documentation for this class was generated from the following file: