.\" Copyright (c) 1990, 1991, 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" This code is derived from software contributed to Berkeley by .\" the American National Standards Committee X3, on Information .\" Processing Systems. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 4. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)qsort.3 8.1 (Berkeley) 6/4/93 .\" $FreeBSD: src/lib/libc/stdlib/qsort.3,v 1.17 2007/01/09 00:28:10 imp Exp $ .\" .Dd Nov 25, 2008 .Dt PSORT 3 .Os "Mac OS X" .Sh NAME .Nm psort , #ifdef UNIFDEF_BLOCKS .Nm psort_b , #endif .Nm psort_r .Nd parallel sort functions .Sh SYNOPSIS .In stdlib.h .Ft void .Fo psort .Fa "void *base" .Fa "size_t nel" .Fa "size_t width" .Fa "int \*[lp]*compar\*[rp]\*[lp]const void *, const void *\*[rp]" .Fc #ifdef UNIFDEF_BLOCKS .Ft void .Fo psort_b .Fa "void *base" .Fa "size_t nel" .Fa "size_t width" .Fa "int \*[lp]^compar\*[rp]\*[lp]const void *, const void *\*[rp]" .Fc #endif .Ft void .Fo psort_r .Fa "void *base" .Fa "size_t nel" .Fa "size_t width" .Fa "void *thunk" .Fa "int \*[lp]*compar\*[rp]\*[lp]void *, const void *, const void *\*[rp]" .Fc .Sh DESCRIPTION The #ifdef UNIFDEF_BLOCKS .Fn psort , .Fn psort_b , #else .Fn psort #endif and .Fn psort_r functions are parallel sort routines that are drop-in compatible with the corresponding .Fn qsort function (see .Xr qsort 3 for a description of the arguments). On multiprocessor 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 .Fn qsort . .Sh 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 .Em 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. .Pp Additional memory is temporary allocated to deal with the parallel nature of the computation. .Pp Because of the overhead of maintaining multiple threads, the .Fn psort family of routines may choose to just call .Xr 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). .Pp Like .Xr qsort 3 , the sort is not stable. .Sh RETURN VALUES The #ifdef UNIFDEF_BLOCKS .Fn psort , .Fn psort_b #else .Fn psort #endif and .Fn psort_r functions return no value. .Sh SEE ALSO .Xr qsort 3 .Sh SEE ALSO .Xr sort 1 , .Xr radixsort 3 .Rs .%A Hoare, C.A.R. .%D 1962 .%T "Quicksort" .%J "The Computer Journal" .%V 5:1 .%P pp. 10-15 .Re .Rs .%A Williams, J.W.J .%D 1964 .%T "Heapsort" .%J "Communications of the ACM" .%V 7:1 .%P pp. 347-348 .Re .Rs .%A Knuth, D.E. .%D 1968 .%B "The Art of Computer Programming" .%V Vol. 3 .%T "Sorting and Searching" .%P pp. 114-123, 145-149 .Re .Rs .%A McIlroy, P.M. .%T "Optimistic Sorting and Information Theoretic Complexity" .%J "Fourth Annual ACM-SIAM Symposium on Discrete Algorithms" .%V January 1992 .Re .Rs .%A Bentley, J.L. .%A McIlroy, M.D. .%T "Engineering a Sort Function" .%J "Software--Practice and Experience" .%V Vol. 23(11) .%P pp. 1249-1265 .%D November\ 1993 .Re .Sh STANDARDS The .Fn qsort function conforms to .St -isoC .