[apple/libc.git] / stdlib / psort.3

.\" 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.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 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 1.15 2004/07/02 23:52:12 ru 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
Commit	Line	Data
34e8f829 A	1	.\" Copyright (c) 1990, 1991, 1993
	2	.\" The Regents of the University of California. All rights reserved.
	3	.\"
	4	.\" This code is derived from software contributed to Berkeley by
	5	.\" the American National Standards Committee X3, on Information
	6	.\" Processing Systems.
	7	.\"
	8	.\" Redistribution and use in source and binary forms, with or without
	9	.\" modification, are permitted provided that the following conditions
	10	.\" are met:
	11	.\" 1. Redistributions of source code must retain the above copyright
	12	.\" notice, this list of conditions and the following disclaimer.
	13	.\" 2. Redistributions in binary form must reproduce the above copyright
	14	.\" notice, this list of conditions and the following disclaimer in the
	15	.\" documentation and/or other materials provided with the distribution.
	16	.\" 3. All advertising materials mentioning features or use of this software
	17	.\" must display the following acknowledgement:
	18	.\" This product includes software developed by the University of
	19	.\" California, Berkeley and its contributors.
	20	.\" 4. Neither the name of the University nor the names of its contributors
	21	.\" may be used to endorse or promote products derived from this software
	22	.\" without specific prior written permission.
	23	.\"
	24	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	25	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	26	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	27	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	28	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	29	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	30	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	31	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	32	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	33	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	34	.\" SUCH DAMAGE.
	35	.\"
	36	.\" @(#)qsort.3 8.1 (Berkeley) 6/4/93
	37	.\" $FreeBSD: src/lib/libc/stdlib/qsort.3,v 1.15 2004/07/02 23:52:12 ru Exp $
	38	.\"
	39	.Dd Nov 25, 2008
	40	.Dt PSORT 3
	41	.Os "Mac OS X"
	42	.Sh NAME
	43	.Nm psort ,
	44	#ifdef UNIFDEF_BLOCKS
	45	.Nm psort_b ,
	46	#endif
	47	.Nm psort_r
	48	.Nd parallel sort functions
	49	.Sh SYNOPSIS
	50	.In stdlib.h
	51	.Ft void
	52	.Fo psort
	53	.Fa "void *base"
	54	.Fa "size_t nel"
	55	.Fa "size_t width"
	56	.Fa "int \[lp]compar\[rp]\[lp]const void , const void \*[rp]"
	57	.Fc
	58	#ifdef UNIFDEF_BLOCKS
	59	.Ft void
	60	.Fo psort_b
	61	.Fa "void *base"
	62	.Fa "size_t nel"
	63	.Fa "size_t width"
	64	.Fa "int \[lp]^compar\[rp]\[lp]const void , const void \[rp]"
65	.Fc
66	#endif
67	.Ft void
68	.Fo psort_r
69	.Fa "void *base"
70	.Fa "size_t nel"
71	.Fa "size_t width"
72	.Fa "void *thunk"
73	.Fa "int \[lp]compar\[rp]\[lp]void , const void , const void \[rp]"
74	.Fc
75	.Sh DESCRIPTION
76	The
77	#ifdef UNIFDEF_BLOCKS
78	.Fn psort ,
79	.Fn psort_b ,
80	#else
81	.Fn psort
82	#endif
83	and
84	.Fn psort_r
85	functions are parallel sort routines that are drop-in compatible with the
86	corresponding
87	.Fn qsort
88	function (see
89	.Xr qsort 3
90	for a description of the arguments).
91	On multiprocessor machines, multiple threads may be created to simultaneously
92	perform the sort calculations, resulting in an overall faster sort result.
93	Overhead in managing the threads limits the maximum speed improvement to
94	somewhat less that the number of processors available.
95	For example, on a 4-processor machine, a typical sort on a large array might
96	result in 3.2 times faster sorting than a regular
97	.Fn qsort .
98	.Sh RESTRICTIONS
99	Because of the multi-threaded nature of the sort, the comparison function
100	is expected to perform its own synchronization that might be required for
101	data physically
102	.Em outside
103	the two objects passed to the comparison function.
104	However, no synchronization is required for the two
105	object themselves, unless some third party is also accessing those objects.
106	.Pp
107	Additional memory is temporary allocated to deal with the parallel nature
108	of the computation.
109	.Pp
110	Because of the overhead of maintaining multiple threads, the
111	.Fn psort
112	family of routines may choose to just call
113	.Xr qsort 3
114	when there is no advantage to parallelizing (for example, when the number of
115	objects in the array is too small, or only one processor is available).
116	.Pp
117	Like
118	.Xr qsort 3 ,
119	the sort is not stable.
120	.Sh RETURN VALUES
121	The
122	#ifdef UNIFDEF_BLOCKS
123	.Fn psort ,
124	.Fn psort_b
125	#else
126	.Fn psort
127	#endif
128	and
129	.Fn psort_r
130	functions
131	return no value.
132	.Sh SEE ALSO
133	.Xr qsort 3