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coveb

NAME

coveb - cache oblivious high speed 32-bit priority queue for large data sets

SYNOPSIS

coveb : library for space and time efficient manipulation of unsigned 32-bit integers.

DESCRIPTION

please see coveb-tree.h or the included README for details.

#include <coveb.h>

Instantiation:

struct coveb_bq *q;

q = coveb_bq_new();

This allocates a new cache-oblivious bitwise priority queue. To free, use:

Deallocation:

coveb_bq_free(q);

Insertion of 32-bit unsigned integer values:

void coveb_bq_insert(struct coveb_bq *q, uint32_t x);

places a new value into the queue, or does nothing if it's already there.

Removal of values:

uint32_t coveb_bq_extractmin(struct coveb_bq *q);

removes the smallest value (min) from the queue and returns it. It is illegal to try to remove a value from an empty (size = 0) queue. This is the fastest way to remove elements.

uint32_t coveb_bq_remove(struct coveb_bq *q, uint32_t x);

This generic function removes any specific value from the queue. It returns 0 if the object was already in the queue, and 1 if not.

Queue status monitoring:

When the queue is completely full (containing four 'binary' gigasamples), it consumes about one gigabyte of memory. This means that it uses about 2 bits per sample on average when full. This is only about twice as big as the literal storage cost of a typical queue state. Because this size is not reportable as a 32-bit integer, the following function is available to detect the full queue condition:

uint32_t coveb_bq_addresses_full(const struct coveb_bq *q);

Returns 1 if all 2 ** 32 elements are in the queue, or 0 otherwise. When the queue is not full, the normal size function is exactly accurate:

uint32_t coveb_bq_size(const struct coveb_bq *q);

returns the count of integers currently stored in the queue. This can be used to see if an element can be extracted safely (size > 0). Note that in the special case where the queue is completely full and therefore the number of elements in the queue is one greater than the maximum value of an unsigned 32-bit integer, the size function will return instead one less than the actual number of elements. To detect this uncommon condition use coveb_bq_addresses_full.

Extrema functions

uint32_t coveb_bq_max(const struct coveb_bq *q);

 returns the largest integer stored in the queue without removal.

uint32_t coveb_bq_min(const struct coveb_bq *q);

 returns the smallest integer stored in the queue without removal.

Rangefinding functions

void coveb_bq_locate_smallest_not_less_than(const struct coveb_bq *q, uint32_t incl_lower_bound, uint32_t *result_x, uint32_t *gotresult);

searches for an integer stored in the queue that is not less than incl_lower_bound. If there is more than one such integer, the smallest is returned. If an integer is found, *gotresult will be set to 1 and *result_x will hold the integer that was found. If no such integer is found in the queue, then *gotresult with be set to 0 and *result_x will be untouched. The queue is not modified in any case.

void coveb_bq_successor(const struct coveb_bq *q, uint32_t excl_lower_bound, uint32_t *result_x, uint32_t *gotresult);

This function scans upward for an integer that is greater than excl_lower_bound. It is otherwise the same as the coveb_bq_locate_smallest_not_less_than function.

This library uses a data structure inspired by Peter van Emde Boas.

ENVIRONMENT

none

DIAGNOSTICS

The failout(msg) macro may be redefined using #define FAILOUT_FUNC(msg)

SEE ALSO