Class search_vec (o2scl)

O2scl : Class List

template<class vec_t, class fp_t = double>
class search_vec

Searching class for monotonic data with caching.

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().

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 o2scl::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.

Note

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. Copy constructors are also private to prevent confusing situations which arise when bit-copying pointers.

Public Functions

inline search_vec()

Create a blank searching object.

inline search_vec(size_t nn, const vec_t &x)

Create a searching object with vector x of size nn.

inline void set_vec(size_t nn, const vec_t &x)

Set the vector to be searched.

inline size_t find(const fp_t x0)

Search an increasing or decreasing vector for the interval containing x0

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

inline size_t find_const(const fp_t x0, size_t &lcache) const

Const version of find()

inline size_t find_inc(const fp_t x0)

Search an increasing vector for the interval containing x0

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.

inline size_t find_inc_const(const fp_t x0, size_t &lcache) const

Const version of find_inc()

inline size_t find_dec(const fp_t x0)

Search a decreasing vector for the interval containing x0

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.

inline size_t find_dec_const(const fp_t x0, size_t &lcache) const

Const version of find_dec()

inline size_t ordered_lookup(const fp_t x0) const

Find the index of x0 in the ordered array x.

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.

Generally, if there are two adjacent entries with the same value, this function will return the entry with the smaller index.

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.

Protected Attributes

const vec_t *v

The vector to be searched.

size_t n

The vector size.

Private Functions

search_vec(const search_vec<vec_t, fp_t>&)

search_vec<vec_t, fp_t> &operator=(const search_vec<vec_t, fp_t>&)