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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() function (see qsort(3) for a description of the arguments).  On multi-processor multiprocessor
     processor machines, multiple threads may be created to simultaneously perform the sort calculations,
     resulting in an overall faster sort result.  Overhead in managing the threads limits the maximum speed
     improvement 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'').

Mac OS X                         Nov 25, 2008                         Mac OS X