/*----------------------------------------------------------------------
SDDPACK: Software for the Semidiscrete Decomposition.
Copyright (c) 1999 Tamara G. Kolda and Dianne P. O'Leary.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA.
This next piece of code is a customized version of the GNU qsort for
the data type we are sorting here. It will be used if the -DQSORTOPT
flag is used in compliation. It should generally make the code
faster, but may be incompatible with some machine types. To
determine if this qsort will work for you, first compile without the
flag, time and test the code. Then try the same thing again with the
flag on. If you do not get the same answers or the code is slower,
than you should not use this option.
----------------------------------------------------------------------*/
#ifdef QSORTOPT
#include /* used by our optimized qsort */
/* Slightly Modified so the compare operation is in-lined. -T. Kolda */
/* Plug-compatible replacement for UNIX qsort.
Copyright (C) 1989 Free Software Foundation, Inc.
Written by Douglas C. Schmidt (schmidt@ics.uci.edu)
This file is part of GNU CC.
GNU QSORT is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
GNU QSORT is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with GNU QSORT; see the file COPYING. If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
#ifdef sparc
#include
#endif
/* Invoke the comparison function, returns either 0, < 0, or > 0. */
#define CMP(A,B) (((sdddouble_plus*)(B))->val - ((sdddouble_plus*)(A))->val)
#define size (sizeof(sdddouble_plus))
/* Byte-wise swap two items of size SIZE. */
#define SWAP(A,B,SIZE) do {int sz = (SIZE); char *a = (A); char *b = (B); \
do { char _temp = *a;*a++ = *b;*b++ = _temp;} while (--sz);} while (0)
/* Copy SIZE bytes from item B to item A. */
#define COPY(A,B,SIZE) {int sz = (SIZE); do { *(A)++ = *(B)++; } while (--sz); }
/* This should be replaced by a standard ANSI macro. */
#ifndef BYTES_PER_WORD
#define BYTES_PER_WORD (sizeof(ulong))
#endif
/* The next 4 #defines implement a very fast in-line stack abstraction. */
#define STACK_SIZE (BYTES_PER_WORD * sizeof (long))
#define PUSH(LOW,HIGH) do {top->lo = LOW;top++->hi = HIGH;} while (0)
#define POP(LOW,HIGH) do {LOW = (--top)->lo;HIGH = top->hi;} while (0)
#define STACK_NOT_EMPTY (stack < top)
/* Discontinue quicksort algorithm when partition gets below this size.
This particular magic number was chosen to work best on a Sun 4/260. */
#define MAX_THRESH 4
/* Stack node declarations used to store unfulfilled partition obligations. */
typedef struct
{
char *lo;
char *hi;
} stack_node;
/* Order size using quicksort. This implementation incorporates
four optimizations discussed in Sedgewick:
1. Non-recursive, using an explicit stack of pointer that store the
next array partition to sort. To save time, this maximum amount
of space required to store an array of MAX_INT is allocated on the
stack. Assuming a 32-bit integer, this needs only 32 *
sizeof (stack_node) == 136 bits. Pretty cheap, actually.
2. Chose the pivot element using a median-of-three decision tree.
This reduces the probability of selecting a bad pivot value and
eliminates certain extraneous comparisons.
3. Only quicksorts TOTAL_ELEMS / MAX_THRESH partitions, leaving
insertion sort to order the MAX_THRESH items within each partition.
This is a big win, since insertion sort is faster for small, mostly
sorted array segments.
4. The larger of the two sub-partitions is always pushed onto the
stack first, with the algorithm then concentrating on the
smaller partition. This *guarantees* no more than log (n)
stack size is needed (actually O(1) in this case)! */
int qsortopt (char *base_ptr, int total_elems)
{
/* Allocating SIZE bytes for a pivot buffer facilitates a better
algorithm below since we can do comparisons directly on the pivot. */
char *pivot_buffer = (char *) alloca (size);
int max_thresh = MAX_THRESH * size;
if (total_elems > MAX_THRESH)
{
char *lo = base_ptr;
char *hi = lo + size * (total_elems - 1);
stack_node stack[STACK_SIZE]; /* Largest size needed for 32-bit int!!! */
stack_node *top = stack + 1;
while (STACK_NOT_EMPTY)
{
char *left_ptr;
char *right_ptr;
{
char *pivot = pivot_buffer;
{
/* Select median value from among LO, MID, and HI. Rearrange
LO and HI so the three values are sorted. This lowers the
probability of picking a pathological pivot value and
skips a comparison for both the LEFT_PTR and RIGHT_PTR. */
char *mid = lo + size * ((hi - lo) / size >> 1);
if (CMP (mid, lo) < 0)
SWAP (mid, lo, size);
if (CMP (hi, mid) < 0)
SWAP (mid, hi, size);
else
goto jump_over;
if (CMP (mid, lo) < 0)
SWAP (mid, lo, size);
jump_over:
COPY (pivot, mid, size);
pivot = pivot_buffer;
}
left_ptr = lo + size;
right_ptr = hi - size;
/* Here's the famous ``collapse the walls'' section of quicksort.
Gotta like those tight inner loops! They are the main reason
that this algorithm runs much faster than others. */
do
{
while (CMP (left_ptr, pivot) < 0)
left_ptr += size;
while (CMP (pivot, right_ptr) < 0)
right_ptr -= size;
if (left_ptr < right_ptr)
{
SWAP (left_ptr, right_ptr, size);
left_ptr += size;
right_ptr -= size;
}
else if (left_ptr == right_ptr)
{
left_ptr += size;
right_ptr -= size;
break;
}
}
while (left_ptr <= right_ptr);
}
/* Set up pointers for next iteration. First determine whether
left and right partitions are below the threshold size. If so,
ignore one or both. Otherwise, push the larger partition's
bounds on the stack and continue sorting the smaller one. */
if ((right_ptr - lo) <= max_thresh)
{
if ((hi - left_ptr) <= max_thresh) /* Ignore both small
partitions. */
POP (lo, hi);
else /* Ignore small left partition. */
lo = left_ptr;
}
else if ((hi - left_ptr) <= max_thresh) /* Ignore small
right partition. */
hi = right_ptr;
else if ((right_ptr - lo) > (hi - left_ptr)) /* Push larger
left
partition
indices. */
{
PUSH (lo, right_ptr);
lo = left_ptr;
}
else /* Push larger right partition indices. */
{
PUSH (left_ptr, hi);
hi = right_ptr;
}
}
}
/* Once the BASE_PTR array is partially sorted by quicksort the rest
is completely sorted using insertion sort, since this is efficient
for partitions below MAX_THRESH size. BASE_PTR points to the beginning
of the array to sort, and END_PTR points at the very last element in
the array (*not* one beyond it!). */
#define MIN(X,Y) ((X) < (Y) ? (X) : (Y))
{
char *end_ptr = base_ptr + size * (total_elems - 1);
char *run_ptr;
char *tmp_ptr = base_ptr;
char *thresh = MIN (end_ptr, base_ptr + max_thresh);
/* Find smallest element in first threshold and place it at the
array's beginning. This is the smallest array element,
and the operation speeds up insertion sort's inner loop. */
for (run_ptr = tmp_ptr + size; run_ptr <= thresh; run_ptr += size)
if (CMP (run_ptr, tmp_ptr) < 0)
tmp_ptr = run_ptr;
if (tmp_ptr != base_ptr)
SWAP (tmp_ptr, base_ptr, size);
/* Insertion sort, running from left-hand-side up to `right-hand-side.'
Pretty much straight out of the original GNU qsort routine. */
for (run_ptr = base_ptr + size; (tmp_ptr = run_ptr += size) <= end_ptr; )
{
while (CMP (run_ptr, tmp_ptr -= size) < 0)
;
if ((tmp_ptr += size) != run_ptr)
{
char *trav;
for (trav = run_ptr + size; --trav >= run_ptr;)
{
char c = *trav;
char *hi, *lo;
for (hi = lo = trav; (lo -= size) >= tmp_ptr; hi = lo)
*hi = *lo;
*hi = c;
}
}
}
}
return 1;
}
#endif