Page MenuHome
Differential D6807 Diff 21646 extern/opennurbs/opennurbs_quacksort_template.h

Changeset View

Standalone View

View Options

extern/opennurbs/opennurbs_quacksort_template.h

  • This file was added.
/* $NoKeywords: $ */
/*
//
// Copyright (c) 1993-2011 Robert McNeel & Associates. All rights reserved.
// OpenNURBS, Rhinoceros, and Rhino3D are registered trademarks of Robert
// McNeel & Assoicates.
//
// THIS SOFTWARE IS PROVIDED "AS IS" WITHOUT EXPRESS OR IMPLIED WARRANTY.
// ALL IMPLIED WARRANTIES OF FITNESS FOR ANY PARTICULAR PURPOSE AND OF
// MERCHANTABILITY ARE HEREBY DISCLAIMED.
//
// For complete openNURBS copyright information see <http://www.opennurbs.org>.
//
////////////////////////////////////////////////////////////////
*/
/*
See opennurbs_sort.cpp for examples showing how to use
opennurbs_quacksort_template.h to define type specific
sorting functions.
*/
#if !defined(ON_QSORT_FNAME)
#error Define ON_QSORT_FNAME macro before including opennurbs_quacksort_template.h
#endif
// ON_SORT_TEMPLATE_TYPE -> double, int, ....
#if !defined(ON_SORT_TEMPLATE_TYPE)
#define BASETYPE void *
#define DATATYPE unsigned char
#define DATAWIDTH m_width
#define Swap(a,b) m_swapfunc(a,b,m_width)
#if defined(ON_SORT_TEMPLATE_USE_CONTEXT)
// use a compare function with context parameter
#define GreaterThan(A,B) m_compare(m_context,A,B) > 0
#else
// use a compare function without context parameter
#define GreaterThan(A,B) m_compare(A,B) > 0
#endif
#else
#define BASETYPE ON_SORT_TEMPLATE_TYPE *
#define DATATYPE ON_SORT_TEMPLATE_TYPE
#define DATAWIDTH 1
#if defined(ON_SORT_TEMPLATE_USE_SWAP)
#define Swap(a,b) m_swapfunc(a,b,m_width)
#else
// use intrinsic assigment
#define Swap(a,b) ON_SORT_TEMPLATE_TYPE tmp = *a; *a = *b; *b = tmp
#endif
#if defined(ON_SORT_TEMPLATE_COMPARE)
// use a compare function like strcmp for char* strings
#define GreaterThan(A,B) ON_SORT_TEMPLATE_COMPARE(A,B) > 0
#else
// use intrinsic type compares
#define GreaterThan(A,B) *A > *B
#endif
#endif
#if !defined(ON_QUACKSORT_SWAP_FUNCS_DEFINED)
#if !defined(ON_SORT_TEMPLATE_TYPE) || defined(ON_SORT_TEMPLATE_USE_SWAP)
// In some files this template is used multiple times.
// The ON_QUACKSORT_SWAP_FUNCS_DEFINED define prevents
// multiple definitions of the static Swap*() functions.
#define ON_QUACKSORT_SWAP_FUNCS_DEFINED
static void SwapChars( unsigned char* a, unsigned char* b, size_t width)
{
do
{
unsigned char x = *a;
*a++ = *b;
*b++ = x;
}
while( --width);
}
static void SwapInts( unsigned char* a, unsigned char* b, size_t width)
{
ON__UINT32* ai = (ON__UINT32*)a;
ON__UINT32* bi = (ON__UINT32*)b;
do
{
ON__UINT32 x = *ai;
*ai++ = *bi;
*bi++ = x;
width -= sizeof(x);
}
while( width);
}
static void SwapBigInts( unsigned char* a, unsigned char* b, size_t width)
{
ON__UINT64* ai = (ON__UINT64*)a;
ON__UINT64* bi = (ON__UINT64*)b;
do
{
ON__UINT64 x = *ai;
*ai++ = *bi;
*bi++ = x;
width -= sizeof(x);
}
while( width);
}
#endif
#endif
// implementation of quick sort with minimum swaps for partition sizes 4 and less
void ON_quacksort(
BASETYPE *base
,size_t nel
#if !defined(ON_SORT_TEMPLATE_TYPE)
,size_t width
#if defined(ON_SORT_TEMPLATE_USE_CONTEXT)
,int (*compar)(void*, const void *, const void *)
,void* context
#else
,int (*compar)(const void *, const void *)
#endif
#endif
)
{
class CSorter
{
public:
DATATYPE *m_base;
size_t m_nel;
const size_t m_width;
int (*m_compar)(const void *, const void *);
void (*m_swapfunc)(unsigned char *, unsigned char *, size_t width);
unsigned int m_rnd;
//#if defined(ON_SORT_TEMPLATE_TYPE) && !defined(ON_SORT_TEMPLATE_USE_SWAP)
// ON_SORT_TEMPLATE_TYPE m_tmp;
//#endif
CSorter(
DATATYPE *base
, size_t nel
, size_t width
, int (*compar)(const void *, const void *)
)
: m_base((DATATYPE*)base)
, m_nel(nel)
, m_width(width)
, m_compar(compar)
, m_rnd(62538161)
{
// When width is a multiple of 8 or 4 (with most arrays it probably is),
// use faster integer swappers instead of byte swapper
if ( 0 == width%sizeof(ON__UINT64))
m_swapfunc = SwapBigInts;
else if ( 0 == width%sizeof(ON__UINT32))
m_swapfunc = SwapInts;
else
m_swapfunc = SwapChars;
};
~CSorter() {};
DATATYPE* Pivot( DATATYPE* base, size_t count)
{
// Uses local quick and dirty pseudorandom number generator to
// give a fuzzy answer to avoid having the data be arranged in
// a way that mechanically always picking the pivot the same way
// affects the speed. Mostly affects chevron etc. patterns.
//
// Totally random pivot would guarantee O(nlogn) worst case, but
// does not perform as well on sorted or nearly sorted sets.
m_rnd *= 1664525;
m_rnd += 1013904223;
unsigned int dice = (m_rnd>>16)&7;
size_t p=count>>1; // 1/2
if ( dice&4)
p += count>>3; // +1/8
if ( dice&2)
p -= count>>4; // -1/16
if ( dice&1)
p -= count>>5; // -1/32
return base + p*DATAWIDTH;
}
void SortSmallRange( DATATYPE* p0, size_t count)
{
// use minimum compares and swaps for 2 to 4 items
switch (count)
{
case 2:
{
DATATYPE* p1 = p0 + DATAWIDTH;
if ( GreaterThan( p0, p1)) { Swap( p0, p1);}
return;
}
case 3:
{
DATATYPE* p1 = p0 + DATAWIDTH;
DATATYPE* p2 = p1 + DATAWIDTH;
bool b = false;
if ( GreaterThan( p0, p1)) { Swap( p0, p1); b = true;}
if ( GreaterThan( p1, p2)) { Swap( p1, p2); b = true;}
if ( b && GreaterThan( p0, p1)) { Swap( p0, p1);}
return;
}
case 4:
{
DATATYPE* p1 = p0 + DATAWIDTH;
DATATYPE* p2 = p1 + DATAWIDTH;
DATATYPE* p3 = p2 + DATAWIDTH;
if ( GreaterThan( p0, p3)) { Swap( p0, p3);}
if ( GreaterThan( p1, p2)) { Swap( p1, p2);}
bool b = false;
if ( GreaterThan( p2, p3)) { Swap( p2, p3); b = true;}
if ( GreaterThan( p0, p1)) { Swap( p0, p1); b = true;}
if ( b && GreaterThan( p1, p2)) { Swap( p1, p2);}
return;
}
}
}
void SortRange( DATATYPE* left, DATATYPE* right)
{
while ( left<right)
{
size_t count = (right-left)/DATAWIDTH+1;
if ( count < 5)
return SortSmallRange( left, count);
DATATYPE* pivotleft;
DATATYPE* pivotright;
// partition range
{
pivotleft = Pivot( left, count);
// move pivot to left end
Swap( left, pivotleft);
pivotleft = left;
pivotright = right + DATAWIDTH;
// move =< pivot to left, and > pivot to right
for(;;)
{
// find next first item > pivot
pivotleft += DATAWIDTH;
if ( pivotleft >= pivotright)
break;
if ( !GreaterThan( pivotleft, left))
continue;
// find next last item =< pivot
do
{
pivotright -= DATAWIDTH;
if ( pivotleft >= pivotright)
goto END; // to quickly exit a nested loop
}
while( GreaterThan( pivotright, left));
Swap( pivotleft, pivotright);
}
END:
pivotright -= DATAWIDTH;
// move pivot to final place
Swap( left, pivotright);
pivotleft = pivotright;
// avoid overhead when not likely that there are multiple items == pivot
if ( pivotright >= right)
{
// the whole range is less or equal than pivot
// check if there are values == pivot left of it. Speeds up sorting arrays with all or lots of equal items.
for ( pivotleft -= DATAWIDTH; pivotleft > left; pivotleft -= DATAWIDTH)
{
if ( GreaterThan( pivotright, pivotleft))
break;
}
pivotleft += DATAWIDTH;
}
}
// limit max recursion depth to log(nel) by only recursing shorter part
if ( pivotleft-left < right-pivotright)
{
// lower part is shorter
SortRange( left, pivotleft-DATAWIDTH);
left = pivotright+DATAWIDTH;
}
else
{
// upper part is shorter
SortRange( pivotright+DATAWIDTH, right);
right = pivotleft-DATAWIDTH;
}
}
}
void Sort()
{
SortRange( m_base, m_base + (m_nel-1)*DATAWIDTH);
}
};
if ( !base || nel < 2 )
return;
#if !defined(ON_SORT_TEMPLATE_TYPE)
if ( width < 1 || !compar)
return;
#endif
CSorter sorter( base, nel, width, compar);
sorter.Sort();
}
#undef Swap
#undef GreaterThan
#undef DATAWIDTH
#undef DATATYPE