ViennaCL - The Vienna Computing Library  1.5.2
Public Types | Public Member Functions | Protected Attributes
const_vector_iterator< SCALARTYPE, ALIGNMENT > Class Template Reference

A STL-type const-iterator for vector elements. Elements can be accessed, but cannot be manipulated. VERY SLOW!! More...

#include <forwards.h>

Inheritance diagram for const_vector_iterator< SCALARTYPE, ALIGNMENT >:
vector_iterator< SCALARTYPE, ALIGNMENT >

Public Types

typedef scalar< SCALARTYPE > value_type
 
typedef vcl_ptrdiff_t difference_type
 
typedef
viennacl::backend::mem_handle 
handle_type
 

Public Member Functions

 const_vector_iterator (vector_base< SCALARTYPE > const &vec, vcl_size_t index, vcl_size_t start=0, vcl_ptrdiff_t stride=1)
 Constructor. More...
 
 const_vector_iterator (handle_type const &elements, vcl_size_t index, vcl_size_t start=0, vcl_ptrdiff_t stride=1)
 Constructor for vector-like treatment of arbitrary buffers. More...
 
value_type operator* (void) const
 Dereferences the iterator and returns the value of the element. For convenience only, performance is poor due to OpenCL overhead! More...
 
self_type operator++ (void)
 
self_type operator++ (int)
 
bool operator== (self_type const &other) const
 
bool operator!= (self_type const &other) const
 
difference_type operator- (self_type const &other) const
 
self_type operator+ (difference_type diff) const
 
vcl_size_t offset () const
 Offset of the current element index with respect to the beginning of the buffer. More...
 
vcl_size_t stride () const
 Index increment in the underlying buffer when incrementing the iterator to the next element. More...
 
handle_type const & handle () const
 

Protected Attributes

handle_type const & elements_
 The index of the entry the iterator is currently pointing to. More...
 
vcl_size_t index_
 
vcl_size_t start_
 
vcl_ptrdiff_t stride_
 

Detailed Description

template<class SCALARTYPE, unsigned int ALIGNMENT>
class viennacl::const_vector_iterator< SCALARTYPE, ALIGNMENT >

A STL-type const-iterator for vector elements. Elements can be accessed, but cannot be manipulated. VERY SLOW!!

Every dereference operation initiates a transfer from the GPU to the CPU. The overhead of such a transfer is around 50us, so 20.000 dereferences take one second. This is four orders of magnitude slower than similar dereferences on the CPU. However, increments and comparisons of iterators is as fast as for CPU types. If you need a fast iterator, copy the whole vector to the CPU first and iterate over the CPU object, e.g. std::vector<float> temp; copy(gpu_vector, temp); for (std::vector<float>::const_iterator iter = temp.begin(); iter != temp.end(); ++iter) { //do something } Note that you may obtain inconsistent data if entries of gpu_vector are manipulated elsewhere in the meanwhile.

Template Parameters
SCALARTYPEThe underlying floating point type (either float or double)
ALIGNMENTAlignment of the underlying vector,
See Also
vector

Member Typedef Documentation

typedef scalar<SCALARTYPE> value_type

Constructor & Destructor Documentation

const_vector_iterator ( vector_base< SCALARTYPE > const &  vec,
vcl_size_t  index,
vcl_size_t  start = 0,
vcl_ptrdiff_t  stride = 1 
)
inline

Constructor.

Parameters
vecThe vector over which to iterate
indexThe starting index of the iterator
startFirst index of the element in the vector pointed to be the iterator (for vector_range and vector_slice)
strideStride for the support of vector_slice
const_vector_iterator ( handle_type const &  elements,
vcl_size_t  index,
vcl_size_t  start = 0,
vcl_ptrdiff_t  stride = 1 
)
inline

Constructor for vector-like treatment of arbitrary buffers.

Parameters
elementsThe buffer over which to iterate
indexThe starting index of the iterator
startFirst index of the element in the vector pointed to be the iterator (for vector_range and vector_slice)
strideStride for the support of vector_slice

Member Function Documentation

handle_type const& handle ( ) const
inline
vcl_size_t offset ( ) const
inline

Offset of the current element index with respect to the beginning of the buffer.

bool operator!= ( self_type const &  other) const
inline
value_type operator* ( void  ) const
inline

Dereferences the iterator and returns the value of the element. For convenience only, performance is poor due to OpenCL overhead!

self_type operator+ ( difference_type  diff) const
inline
self_type operator++ ( void  )
inline
self_type operator++ ( int  )
inline
difference_type operator- ( self_type const &  other) const
inline
bool operator== ( self_type const &  other) const
inline
vcl_size_t stride ( ) const
inline

Index increment in the underlying buffer when incrementing the iterator to the next element.

Field Documentation

handle_type const& elements_
protected

The index of the entry the iterator is currently pointing to.

vcl_size_t index_
protected
vcl_size_t start_
protected
vcl_ptrdiff_t stride_
protected

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