PSORT(3)						   BSD Library Functions Manual 						  PSORT(3)

NAME

     psort, psort_b, psort_r -- parallel sort functions

SYNOPSIS

     #include <stdlib.h>

     void
     psort(void *base, size_t nel, size_t width, int (*compar)(const void *, const void *));

     void
     psort_b(void *base, size_t nel, size_t width, int (^compar)(const void *, const void *));

     void
     psort_r(void *base, size_t nel, size_t width, void *thunk, int (*compar)(void *, const void *, const void *));

DESCRIPTION

     The psort(), psort_b(), and psort_r() functions are parallel sort routines that are drop-in compatible with the corresponding qsort() func-
     tion (see qsort(3) for a description of the arguments).  On multiprocessor machines, multiple threads may be created to simultaneously per-
     form the sort calculations, resulting in an overall faster sort result.  Overhead in managing the threads limits the maximum speed improve-
     ment to somewhat less that the number of processors available.  For example, on a 4-processor machine, a typical sort on a large array might
     result in 3.2 times faster sorting than a regular qsort().

RESTRICTIONS

     Because of the multi-threaded nature of the sort, the comparison function is expected to perform its own synchronization that might be
     required for data physically outside the two objects passed to the comparison function.  However, no synchronization is required for the two
     object themselves, unless some third party is also accessing those objects.

     Additional memory is temporary allocated to deal with the parallel nature of the computation.

     Because of the overhead of maintaining multiple threads, the psort() family of routines may choose to just call qsort(3) when there is no
     advantage to parallelizing (for example, when the number of objects in the array is too small, or only one processor is available).

     Like qsort(3), the sort is not stable.

RETURN VALUES

     The psort(), psort_b() and psort_r() functions return no value.

SEE ALSO

     qsort(3)

SEE ALSO

     sort(1), radixsort(3)

     Hoare, C.A.R., "Quicksort", The Computer Journal, 5:1, pp. 10-15, 1962.

     Williams, J.W.J, "Heapsort", Communications of the ACM, 7:1, pp. 347-348, 1964.

     Knuth, D.E., "Sorting and Searching", The Art of Computer Programming, Vol. 3, pp. 114-123, 145-149, 1968.

     McIlroy, P.M., "Optimistic Sorting and Information Theoretic Complexity", Fourth Annual ACM-SIAM Symposium on Discrete Algorithms, January
     1992.

     Bentley, J.L.  and McIlroy, M.D., "Engineering a Sort Function", Software--Practice and Experience, Vol. 23(11), pp. 1249-1265,
     November 1993.

STANDARDS

     The qsort() function conforms to ISO/IEC 9899:1990 (``ISO C90'').

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