Object-oriented Scientific Computing Library: Version 0.910
Public Member Functions | Protected Attributes
search_vec< vec_t > Class Template Reference

Searching class for monotonic data with caching. More...

#include <search_vec.h>

Inheritance diagram for search_vec< vec_t >:
search_vec_ext< vec_t >

Detailed Description

template<class vec_t>
class search_vec< vec_t >

A searching class for monotonic vectors. A caching system similar to gsl_interp_accel is used.

To find the interval containing a value, use find(). If you happen to know in advance that the vector is increasing or decreasing, then you can use find_inc() or find_dec() instead. To ignore the caching and just use straight binary search, you can use the functions in vector.h .

Alternatively, if you just want to find the index with the element closest to a specified value, use ordered_lookup(). Note that ordered_lookup() is slightly different than ovector_tlate::lookup(), since the latter does not assume the data is monotonic.

The functions find_inc(), find_dec() and find() are designed to return the lower index of an interval containing the desired point, and as a result will never return the last index of a vector, e.g. for a vector of size n they always return a number between 0 and n-2 inclusive. See search_vec_ext for an alternative.

Note:
The behavior of these functions is undefined if some of the user-specified data is not finite or not strictly monotonic. Two adjacent data points should not be equal. This class does not verify that the user-specified data has these properties.
This class does not store a copy of the data, but only a pointer to it. This means that one can safely modify the data after the constructor is called, so long as one does not make the vector smaller (as the cache might then point to a value outside the new vector) and so long as the new vector is still monotonic.
Idea for Future:
Consider a sanity check to ensure that the cache is never larger than the vector length.

Definition at line 77 of file search_vec.h.

Public Member Functions

 search_vec (size_t nn, const vec_t &x)
 Create a searching object with vector x of size nn.
size_t find (const double x0) const
 Search an increasing or decreasing vector for the interval containing x0
size_t find_inc (const double x0) const
 Search an increasing vector for the interval containing x0
size_t find_dec (const double x0) const
 Search a decreasing vector for the interval containing x0
size_t ordered_lookup (const double x0) const
 Find the index of x0 in the ordered array x.

Protected Attributes

size_t cache
 Storage for the most recent index.
const vec_t * v
 The vector to be searched.
const size_t n
 The vector size.

Member Function Documentation

template<class vec_t>
size_t search_vec< vec_t >::find ( const double  x0) const [inline]

This function is identical to find_inc() if the data is increasing, and find_dec() if the data is decreasing.

Reimplemented in search_vec_ext< vec_t >.

Definition at line 116 of file search_vec.h.

template<class vec_t>
size_t search_vec< vec_t >::find_inc ( const double  x0) const [inline]

This function is a cached version of vector_bsearch_inc() , analogous to gsl_interp_accel_find(), except that it does not internally record cache hits and misses.

Reimplemented in search_vec_ext< vec_t >.

Definition at line 130 of file search_vec.h.

template<class vec_t>
size_t search_vec< vec_t >::find_dec ( const double  x0) const [inline]

This function is a cached version of vector_bsearch_dec() . The operation of this function is undefined if the data is not strictly monotonic, i.e. if some of the data elements are equal.

Reimplemented in search_vec_ext< vec_t >.

Definition at line 147 of file search_vec.h.

template<class vec_t>
size_t search_vec< vec_t >::ordered_lookup ( const double  x0) const [inline]

This returns the index i for which x[i] is as close as possible to x0 if x[i] is either increasing or decreasing.

If you have a non-monotonic vector, you can use vector_lookup() instead, or if you a non-monotonic ovector or uvector object, consider using ovector_view_tlate::lookup() or uvector_view_tlate::lookup() instead of this function.

Generally, if there are two adjacent entries with the same value, this function will return the entry with the smaller index. (This is the same as the convention in ovector_view_tlate::lookup() and uvector_view_tlate::lookup() ).

Idea for Future:
This function just uses the find functions and then adjusts the answer at the end if necessary. It might be possible to improve the speed by rewriting this from scratch.

Definition at line 178 of file search_vec.h.


Field Documentation

template<class vec_t>
size_t search_vec< vec_t >::cache [mutable, protected]
Note:
This is marked mutable to ensure const-correctness is straightforward.

Definition at line 88 of file search_vec.h.


The documentation for this class was generated from the following file:
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Documentation generated with Doxygen. Provided under the GNU Free Documentation License (see License Information).

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