}
/*
- * The rest of this file was derived from source code contributed
- * by Tom Horsley.
+ * The mergesort implementation is by Peter M. Mcilroy <pmcilroy@lucent.com>.
+ *
+ * The original code was written in conjunction with BSD Computer Software
+ * Research Group at University of California, Berkeley.
+ *
+ * See also: "Optimistic Merge Sort" (SODA '92)
+ *
+ * The integration to Perl is by John P. Linderman <jpl@rearch.att.com>.
+ *
+ * The code can be distributed under the same terms as Perl itself.
*
- * NOTE: this code was derived from Tom Horsley's qsort replacement
- * and should not be confused with the original code.
*/
-/* Copyright (C) Tom Horsley, 1997. All rights reserved.
-
- Permission granted to distribute under the same terms as perl which are
- (briefly):
-
- This program is free software; you can redistribute it and/or modify
- it under the terms of either:
-
- a) the GNU General Public License as published by the Free
- Software Foundation; either version 1, or (at your option) any
- later version, or
-
- b) the "Artistic License" which comes with this Kit.
-
- Details on the perl license can be found in the perl source code which
- may be located via the www.perl.com web page.
-
- This is the most wonderfulest possible qsort I can come up with (and
- still be mostly portable) My (limited) tests indicate it consistently
- does about 20% fewer calls to compare than does the qsort in the Visual
- C++ library, other vendors may vary.
+#ifdef TESTHARNESS
+#include <sys/types.h>
+typedef void SV;
+#define pTHXo_
+#define pTHX_
+#define STATIC
+#define New(ID,VAR,N,TYPE) VAR=(TYPE *)malloc((N)*sizeof(TYPE))
+#define Safefree(VAR) free(VAR)
+typedef int (*SVCOMPARE_t) (pTHXo_ SV*, SV*);
+#endif /* TESTHARNESS */
+
+typedef char * aptr; /* pointer for arithmetic on sizes */
+typedef SV * gptr; /* pointers in our lists */
+
+/* Binary merge internal sort, with a few special mods
+** for the special perl environment it now finds itself in.
+**
+** Things that were once options have been hotwired
+** to values suitable for this use. In particular, we'll always
+** initialize looking for natural runs, we'll always produce stable
+** output, and we'll always do Peter McIlroy's binary merge.
+*/
- Some of the ideas in here can be found in "Algorithms" by Sedgewick,
- others I invented myself (or more likely re-invented since they seemed
- pretty obvious once I watched the algorithm operate for a while).
+/* Pointer types for arithmetic and storage and convenience casts */
- Most of this code was written while watching the Marlins sweep the Giants
- in the 1997 National League Playoffs - no Braves fans allowed to use this
- code (just kidding :-).
+#define APTR(P) ((aptr)(P))
+#define GPTP(P) ((gptr *)(P))
+#define GPPP(P) ((gptr **)(P))
- I realize that if I wanted to be true to the perl tradition, the only
- comment in this file would be something like:
- ...they shuffled back towards the rear of the line. 'No, not at the
- rear!' the slave-driver shouted. 'Three files up. And stay there...
+/* byte offset from pointer P to (larger) pointer Q */
+#define BYTEOFF(P, Q) (APTR(Q) - APTR(P))
- However, I really needed to violate that tradition just so I could keep
- track of what happens myself, not to mention some poor fool trying to
- understand this years from now :-).
-*/
+#define PSIZE sizeof(gptr)
-/* ********************************************************** Configuration */
+/* If PSIZE is power of 2, make PSHIFT that power, if that helps */
-#ifndef QSORT_ORDER_GUESS
-#define QSORT_ORDER_GUESS 2 /* Select doubling version of the netBSD trick */
+#ifdef PSHIFT
+#define PNELEM(P, Q) (BYTEOFF(P,Q) >> (PSHIFT))
+#define PNBYTE(N) ((N) << (PSHIFT))
+#define PINDEX(P, N) (GPTP(APTR(P) + PNBYTE(N)))
+#else
+/* Leave optimization to compiler */
+#define PNELEM(P, Q) (GPTP(Q) - GPTP(P))
+#define PNBYTE(N) ((N) * (PSIZE))
+#define PINDEX(P, N) (GPTP(P) + (N))
#endif
-/* QSORT_MAX_STACK is the largest number of partitions that can be stacked up for
- future processing - a good max upper bound is log base 2 of memory size
- (32 on 32 bit machines, 64 on 64 bit machines, etc). In reality can
- safely be smaller than that since the program is taking up some space and
- most operating systems only let you grab some subset of contiguous
- memory (not to mention that you are normally sorting data larger than
- 1 byte element size :-).
-*/
-#ifndef QSORT_MAX_STACK
-#define QSORT_MAX_STACK 32
-#endif
+/* Pointer into other corresponding to pointer into this */
+#define POTHER(P, THIS, OTHER) GPTP(APTR(OTHER) + BYTEOFF(THIS,P))
-/* QSORT_BREAK_EVEN is the size of the largest partition we should insertion sort.
- Anything bigger and we use qsort. If you make this too small, the qsort
- will probably break (or become less efficient), because it doesn't expect
- the middle element of a partition to be the same as the right or left -
- you have been warned).
-*/
-#ifndef QSORT_BREAK_EVEN
-#define QSORT_BREAK_EVEN 6
-#endif
+#define FROMTOUPTO(src, dst, lim) do *dst++ = *src++; while(src<lim)
-/* ************************************************************* Data Types */
-/* hold left and right index values of a partition waiting to be sorted (the
- partition includes both left and right - right is NOT one past the end or
- anything like that).
+/* Runs are identified by a pointer in the auxilliary list.
+** The pointer is at the start of the list,
+** and it points to the start of the next list.
+** NEXT is used as an lvalue, too.
*/
-struct partition_stack_entry {
- int left;
- int right;
-#ifdef QSORT_ORDER_GUESS
- int qsort_break_even;
-#endif
-};
-/* ******************************************************* Shorthand Macros */
+#define NEXT(P) (*GPPP(P))
-/* Note that these macros will be used from inside the qsort function where
- we happen to know that the variable 'elt_size' contains the size of an
- array element and the variable 'temp' points to enough space to hold a
- temp element and the variable 'array' points to the array being sorted
- and 'compare' is the pointer to the compare routine.
- Also note that there are very many highly architecture specific ways
- these might be sped up, but this is simply the most generally portable
- code I could think of.
+/* PTHRESH is the minimum number of pairs with the same sense to justify
+** checking for a run and extending it. Note that PTHRESH counts PAIRS,
+** not just elements, so PTHRESH == 8 means a run of 16.
*/
-/* Return < 0 == 0 or > 0 as the value of elt1 is < elt2, == elt2, > elt2
-*/
-#define qsort_cmp(elt1, elt2) \
- ((*compare)(aTHXo_ array[elt1], array[elt2]))
-
-#ifdef QSORT_ORDER_GUESS
-#define QSORT_NOTICE_SWAP swapped++;
-#else
-#define QSORT_NOTICE_SWAP
-#endif
+#define PTHRESH (8)
-/* swaps contents of array elements elt1, elt2.
-*/
-#define qsort_swap(elt1, elt2) \
- STMT_START { \
- QSORT_NOTICE_SWAP \
- temp = array[elt1]; \
- array[elt1] = array[elt2]; \
- array[elt2] = temp; \
- } STMT_END
-
-/* rotate contents of elt1, elt2, elt3 such that elt1 gets elt2, elt2 gets
- elt3 and elt3 gets elt1.
+/* RTHRESH is the number of elements in a run that must compare low
+** to the low element from the opposing run before we justify
+** doing a binary rampup instead of single stepping.
+** In random input, N in a row low should only happen with
+** probability 2^(1-N), so we can risk that we are dealing
+** with orderly input without paying much when we aren't.
*/
-#define qsort_rotate(elt1, elt2, elt3) \
- STMT_START { \
- QSORT_NOTICE_SWAP \
- temp = array[elt1]; \
- array[elt1] = array[elt2]; \
- array[elt2] = array[elt3]; \
- array[elt3] = temp; \
- } STMT_END
-/* ************************************************************ Debug stuff */
+#define RTHRESH (6)
-#ifdef QSORT_DEBUG
-static void
-break_here()
-{
- return; /* good place to set a breakpoint */
-}
+/*
+** Overview of algorithm and variables.
+** The array of elements at list1 will be organized into runs of length 2,
+** or runs of length >= 2 * PTHRESH. We only try to form long runs when
+** PTHRESH adjacent pairs compare in the same way, suggesting overall order.
+**
+** Unless otherwise specified, pair pointers address the first of two elements.
+**
+** b and b+1 are a pair that compare with sense ``sense''.
+** b is the ``bottom'' of adjacent pairs that might form a longer run.
+**
+** p2 parallels b in the list2 array, where runs are defined by
+** a pointer chain.
+**
+** t represents the ``top'' of the adjacent pairs that might extend
+** the run beginning at b. Usually, t addresses a pair
+** that compares with opposite sense from (b,b+1).
+** However, it may also address a singleton element at the end of list1,
+** or it may be equal to ``last'', the first element beyond list1.
+**
+** r addresses the Nth pair following b. If this would be beyond t,
+** we back it off to t. Only when r is less than t do we consider the
+** run long enough to consider checking.
+**
+** q addresses a pair such that the pairs at b through q already form a run.
+** Often, q will equal b, indicating we only are sure of the pair itself.
+** However, a search on the previous cycle may have revealed a longer run,
+** so q may be greater than b.
+**
+** p is used to work back from a candidate r, trying to reach q,
+** which would mean b through r would be a run. If we discover such a run,
+** we start q at r and try to push it further towards t.
+** If b through r is NOT a run, we detect the wrong order at (p-1,p).
+** In any event, after the check (if any), we have two main cases.
+**
+** 1) Short run. b <= q < p <= r <= t.
+** b through q is a run (perhaps trivial)
+** q through p are uninteresting pairs
+** p through r is a run
+**
+** 2) Long run. b < r <= q < t.
+** b through q is a run (of length >= 2 * PTHRESH)
+**
+** Note that degenerate cases are not only possible, but likely.
+** For example, if the pair following b compares with opposite sense,
+** then b == q < p == r == t.
+*/
-#define qsort_assert(t) (void)( (t) || (break_here(), 0) )
static void
-doqsort_all_asserts(
- void * array,
- size_t num_elts,
- size_t elt_size,
- int (*compare)(const void * elt1, const void * elt2),
- int pc_left, int pc_right, int u_left, int u_right)
+dynprep(pTHX_ gptr *list1, gptr *list2, size_t nmemb, SVCOMPARE_t cmp)
{
- int i;
-
- qsort_assert(pc_left <= pc_right);
- qsort_assert(u_right < pc_left);
- qsort_assert(pc_right < u_left);
- for (i = u_right + 1; i < pc_left; ++i) {
- qsort_assert(qsort_cmp(i, pc_left) < 0);
- }
- for (i = pc_left; i < pc_right; ++i) {
- qsort_assert(qsort_cmp(i, pc_right) == 0);
- }
- for (i = pc_right + 1; i < u_left; ++i) {
- qsort_assert(qsort_cmp(pc_right, i) < 0);
- }
+ int sense;
+ register gptr *b, *p, *q, *t, *p2;
+ register gptr c, *last, *r;
+ gptr *savep;
+
+ b = list1;
+ last = PINDEX(b, nmemb);
+ sense = (cmp(aTHX_ *b, *(b+1)) > 0);
+ for (p2 = list2; b < last; ) {
+ /* We just started, or just reversed sense.
+ ** Set t at end of pairs with the prevailing sense.
+ */
+ for (p = b+2, t = p; ++p < last; t = ++p) {
+ if ((cmp(aTHX_ *t, *p) > 0) != sense) break;
+ }
+ q = b;
+ /* Having laid out the playing field, look for long runs */
+ do {
+ p = r = b + (2 * PTHRESH);
+ if (r >= t) p = r = t; /* too short to care about */
+ else {
+ while (((cmp(aTHX_ *(p-1), *p) > 0) == sense) &&
+ ((p -= 2) > q));
+ if (p <= q) {
+ /* b through r is a (long) run.
+ ** Extend it as far as possible.
+ */
+ p = q = r;
+ while (((p += 2) < t) &&
+ ((cmp(aTHX_ *(p-1), *p) > 0) == sense)) q = p;
+ r = p = q + 2; /* no simple pairs, no after-run */
+ }
+ }
+ if (q > b) { /* run of greater than 2 at b */
+ savep = p;
+ p = q += 2;
+ /* pick up singleton, if possible */
+ if ((p == t) &&
+ ((t + 1) == last) &&
+ ((cmp(aTHX_ *(p-1), *p) > 0) == sense))
+ savep = r = p = q = last;
+ p2 = NEXT(p2) = p2 + (p - b);
+ if (sense) while (b < --p) {
+ c = *b;
+ *b++ = *p;
+ *p = c;
+ }
+ p = savep;
+ }
+ while (q < p) { /* simple pairs */
+ p2 = NEXT(p2) = p2 + 2;
+ if (sense) {
+ c = *q++;
+ *(q-1) = *q;
+ *q++ = c;
+ } else q += 2;
+ }
+ if (((b = p) == t) && ((t+1) == last)) {
+ NEXT(p2) = p2 + 1;
+ b++;
+ }
+ q = r;
+ } while (b < t);
+ sense = !sense;
+ }
+ return;
}
-#define qsort_all_asserts(PC_LEFT, PC_RIGHT, U_LEFT, U_RIGHT) \
- doqsort_all_asserts(array, num_elts, elt_size, compare, \
- PC_LEFT, PC_RIGHT, U_LEFT, U_RIGHT)
-#else
-
-#define qsort_assert(t) ((void)0)
+/* Overview of bmerge variables:
+**
+** list1 and list2 address the main and auxiliary arrays.
+** They swap identities after each merge pass.
+** Base points to the original list1, so we can tell if
+** the pointers ended up where they belonged (or must be copied).
+**
+** When we are merging two lists, f1 and f2 are the next elements
+** on the respective lists. l1 and l2 mark the end of the lists.
+** tp2 is the current location in the merged list.
+**
+** p1 records where f1 started.
+** After the merge, a new descriptor is built there.
+**
+** p2 is a ``parallel'' pointer in (what starts as) descriptor space.
+** It is used to identify and delimit the runs.
+**
+** In the heat of determining where q, the greater of the f1/f2 elements,
+** belongs in the other list, b, t and p, represent bottom, top and probe
+** locations, respectively, in the other list.
+** They make convenient temporary pointers in other places.
+*/
-#define qsort_all_asserts(PC_LEFT, PC_RIGHT, U_LEFT, U_RIGHT) ((void)0)
+STATIC void
+S_qsortsv(pTHX_ gptr *list1, size_t nmemb, SVCOMPARE_t cmp)
+{
+ int i, run;
+ int sense;
+ register gptr *f1, *f2, *t, *b, *p, *tp2, *l1, *l2, *q;
+ gptr *aux, *list2, *p2, *last;
+ gptr *base = list1;
+ gptr *p1;
+
+ if (nmemb <= 1) return; /* sorted trivially */
+ New(799,list2,nmemb,gptr); /* allocate auxilliary array */
+ aux = list2;
+ dynprep(aTHX_ list1, list2, nmemb, cmp);
+ last = PINDEX(list2, nmemb);
+ while (NEXT(list2) != last) {
+ /* More than one run remains. Do some merging to reduce runs. */
+ l2 = p1 = list1;
+ for (tp2 = p2 = list2; p2 != last;) {
+ /* The new first run begins where the old second list ended.
+ ** Use the p2 ``parallel'' pointer to identify the end of the run.
+ */
+ f1 = l2;
+ t = NEXT(p2);
+ f2 = l1 = POTHER(t, list2, list1);
+ if (t != last) t = NEXT(t);
+ l2 = POTHER(t, list2, list1);
+ p2 = t;
+ while (f1 < l1 && f2 < l2) {
+ /* If head 1 is larger than head 2, find ALL the elements
+ ** in list 2 strictly less than head1, write them all,
+ ** then head 1. Then compare the new heads, and repeat,
+ ** until one or both lists are exhausted.
+ **
+ ** In all comparisons (after establishing
+ ** which head to merge) the item to merge
+ ** (at pointer q) is the first operand of
+ ** the comparison. When we want to know
+ ** if ``q is strictly less than the other'',
+ ** we can't just do
+ ** cmp(q, other) < 0
+ ** because stability demands that we treat equality
+ ** as high when q comes from l2, and as low when
+ ** q was from l1. So we ask the question by doing
+ ** cmp(q, other) <= sense
+ ** and make sense == 0 when equality should look low,
+ ** and -1 when equality should look high.
+ */
+
+
+ if (cmp(aTHX_ *f1, *f2) <= 0) {
+ q = f2; b = f1; t = l1;
+ sense = -1;
+ } else {
+ q = f1; b = f2; t = l2;
+ sense = 0;
+ }
-#endif
-/* ****************************************************************** qsort */
+ /* ramp up
+ **
+ ** Leave t at something strictly
+ ** greater than q (or at the end of the list),
+ ** and b at something strictly less than q.
+ */
+ for (i = 1, run = 0 ;;) {
+ if ((p = PINDEX(b, i)) >= t) {
+ /* off the end */
+ if (((p = PINDEX(t, -1)) > b) &&
+ (cmp(aTHX_ *q, *p) <= sense))
+ t = p;
+ else b = p;
+ break;
+ } else if (cmp(aTHX_ *q, *p) <= sense) {
+ t = p;
+ break;
+ } else b = p;
+ if (++run >= RTHRESH) i += i;
+ }
-STATIC void
-S_qsortsv(pTHX_ SV ** array, size_t num_elts, SVCOMPARE_t compare)
-{
- register SV * temp;
- struct partition_stack_entry partition_stack[QSORT_MAX_STACK];
- int next_stack_entry = 0;
+ /* q is known to follow b and must be inserted before t.
+ ** Increment b, so the range of possibilities is [b,t).
+ ** Round binary split down, to favor early appearance.
+ ** Adjust b and t until q belongs just before t.
+ */
- int part_left;
- int part_right;
-#ifdef QSORT_ORDER_GUESS
- int qsort_break_even;
- int swapped;
-#endif
+ b++;
+ while (b < t) {
+ p = PINDEX(b, (PNELEM(b, t) - 1) / 2);
+ if (cmp(aTHX_ *q, *p) <= sense) {
+ t = p;
+ } else b = p + 1;
+ }
- /* Make sure we actually have work to do.
- */
- if (num_elts <= 1) {
- return;
- }
-
- /* Setup the initial partition definition and fall into the sorting loop
- */
- part_left = 0;
- part_right = (int)(num_elts - 1);
-#ifdef QSORT_ORDER_GUESS
- qsort_break_even = QSORT_BREAK_EVEN;
-#else
-#define qsort_break_even QSORT_BREAK_EVEN
-#endif
- for ( ; ; ) {
- if ((part_right - part_left) >= qsort_break_even) {
- /* OK, this is gonna get hairy, so lets try to document all the
- concepts and abbreviations and variables and what they keep
- track of:
-
- pc: pivot chunk - the set of array elements we accumulate in the
- middle of the partition, all equal in value to the original
- pivot element selected. The pc is defined by:
-
- pc_left - the leftmost array index of the pc
- pc_right - the rightmost array index of the pc
-
- we start with pc_left == pc_right and only one element
- in the pivot chunk (but it can grow during the scan).
-
- u: uncompared elements - the set of elements in the partition
- we have not yet compared to the pivot value. There are two
- uncompared sets during the scan - one to the left of the pc
- and one to the right.
-
- u_right - the rightmost index of the left side's uncompared set
- u_left - the leftmost index of the right side's uncompared set
-
- The leftmost index of the left sides's uncompared set
- doesn't need its own variable because it is always defined
- by the leftmost edge of the whole partition (part_left). The
- same goes for the rightmost edge of the right partition
- (part_right).
-
- We know there are no uncompared elements on the left once we
- get u_right < part_left and no uncompared elements on the
- right once u_left > part_right. When both these conditions
- are met, we have completed the scan of the partition.
-
- Any elements which are between the pivot chunk and the
- uncompared elements should be less than the pivot value on
- the left side and greater than the pivot value on the right
- side (in fact, the goal of the whole algorithm is to arrange
- for that to be true and make the groups of less-than and
- greater-then elements into new partitions to sort again).
-
- As you marvel at the complexity of the code and wonder why it
- has to be so confusing. Consider some of the things this level
- of confusion brings:
-
- Once I do a compare, I squeeze every ounce of juice out of it. I
- never do compare calls I don't have to do, and I certainly never
- do redundant calls.
-
- I also never swap any elements unless I can prove there is a
- good reason. Many sort algorithms will swap a known value with
- an uncompared value just to get things in the right place (or
- avoid complexity :-), but that uncompared value, once it gets
- compared, may then have to be swapped again. A lot of the
- complexity of this code is due to the fact that it never swaps
- anything except compared values, and it only swaps them when the
- compare shows they are out of position.
- */
- int pc_left, pc_right;
- int u_right, u_left;
-
- int s;
-
- pc_left = ((part_left + part_right) / 2);
- pc_right = pc_left;
- u_right = pc_left - 1;
- u_left = pc_right + 1;
-
- /* Qsort works best when the pivot value is also the median value
- in the partition (unfortunately you can't find the median value
- without first sorting :-), so to give the algorithm a helping
- hand, we pick 3 elements and sort them and use the median value
- of that tiny set as the pivot value.
-
- Some versions of qsort like to use the left middle and right as
- the 3 elements to sort so they can insure the ends of the
- partition will contain values which will stop the scan in the
- compare loop, but when you have to call an arbitrarily complex
- routine to do a compare, its really better to just keep track of
- array index values to know when you hit the edge of the
- partition and avoid the extra compare. An even better reason to
- avoid using a compare call is the fact that you can drop off the
- edge of the array if someone foolishly provides you with an
- unstable compare function that doesn't always provide consistent
- results.
-
- So, since it is simpler for us to compare the three adjacent
- elements in the middle of the partition, those are the ones we
- pick here (conveniently pointed at by u_right, pc_left, and
- u_left). The values of the left, center, and right elements
- are refered to as l c and r in the following comments.
- */
-
-#ifdef QSORT_ORDER_GUESS
- swapped = 0;
-#endif
- s = qsort_cmp(u_right, pc_left);
- if (s < 0) {
- /* l < c */
- s = qsort_cmp(pc_left, u_left);
- /* if l < c, c < r - already in order - nothing to do */
- if (s == 0) {
- /* l < c, c == r - already in order, pc grows */
- ++pc_right;
- qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1);
- } else if (s > 0) {
- /* l < c, c > r - need to know more */
- s = qsort_cmp(u_right, u_left);
- if (s < 0) {
- /* l < c, c > r, l < r - swap c & r to get ordered */
- qsort_swap(pc_left, u_left);
- qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1);
- } else if (s == 0) {
- /* l < c, c > r, l == r - swap c&r, grow pc */
- qsort_swap(pc_left, u_left);
- --pc_left;
- qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1);
- } else {
- /* l < c, c > r, l > r - make lcr into rlc to get ordered */
- qsort_rotate(pc_left, u_right, u_left);
- qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1);
- }
- }
- } else if (s == 0) {
- /* l == c */
- s = qsort_cmp(pc_left, u_left);
- if (s < 0) {
- /* l == c, c < r - already in order, grow pc */
- --pc_left;
- qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1);
- } else if (s == 0) {
- /* l == c, c == r - already in order, grow pc both ways */
- --pc_left;
- ++pc_right;
- qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1);
- } else {
- /* l == c, c > r - swap l & r, grow pc */
- qsort_swap(u_right, u_left);
- ++pc_right;
- qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1);
- }
- } else {
- /* l > c */
- s = qsort_cmp(pc_left, u_left);
- if (s < 0) {
- /* l > c, c < r - need to know more */
- s = qsort_cmp(u_right, u_left);
- if (s < 0) {
- /* l > c, c < r, l < r - swap l & c to get ordered */
- qsort_swap(u_right, pc_left);
- qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1);
- } else if (s == 0) {
- /* l > c, c < r, l == r - swap l & c, grow pc */
- qsort_swap(u_right, pc_left);
- ++pc_right;
- qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1);
- } else {
- /* l > c, c < r, l > r - rotate lcr into crl to order */
- qsort_rotate(u_right, pc_left, u_left);
- qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1);
- }
- } else if (s == 0) {
- /* l > c, c == r - swap ends, grow pc */
- qsort_swap(u_right, u_left);
- --pc_left;
- qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1);
- } else {
- /* l > c, c > r - swap ends to get in order */
- qsort_swap(u_right, u_left);
- qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1);
- }
- }
- /* We now know the 3 middle elements have been compared and
- arranged in the desired order, so we can shrink the uncompared
- sets on both sides
- */
- --u_right;
- ++u_left;
- qsort_all_asserts(pc_left, pc_right, u_left, u_right);
-
- /* The above massive nested if was the simple part :-). We now have
- the middle 3 elements ordered and we need to scan through the
- uncompared sets on either side, swapping elements that are on
- the wrong side or simply shuffling equal elements around to get
- all equal elements into the pivot chunk.
- */
-
- for ( ; ; ) {
- int still_work_on_left;
- int still_work_on_right;
-
- /* Scan the uncompared values on the left. If I find a value
- equal to the pivot value, move it over so it is adjacent to
- the pivot chunk and expand the pivot chunk. If I find a value
- less than the pivot value, then just leave it - its already
- on the correct side of the partition. If I find a greater
- value, then stop the scan.
- */
- while ((still_work_on_left = (u_right >= part_left))) {
- s = qsort_cmp(u_right, pc_left);
- if (s < 0) {
- --u_right;
- } else if (s == 0) {
- --pc_left;
- if (pc_left != u_right) {
- qsort_swap(u_right, pc_left);
- }
- --u_right;
- } else {
- break;
- }
- qsort_assert(u_right < pc_left);
- qsort_assert(pc_left <= pc_right);
- qsort_assert(qsort_cmp(u_right + 1, pc_left) <= 0);
- qsort_assert(qsort_cmp(pc_left, pc_right) == 0);
- }
- /* Do a mirror image scan of uncompared values on the right
- */
- while ((still_work_on_right = (u_left <= part_right))) {
- s = qsort_cmp(pc_right, u_left);
- if (s < 0) {
- ++u_left;
- } else if (s == 0) {
- ++pc_right;
- if (pc_right != u_left) {
- qsort_swap(pc_right, u_left);
- }
- ++u_left;
- } else {
- break;
- }
- qsort_assert(u_left > pc_right);
- qsort_assert(pc_left <= pc_right);
- qsort_assert(qsort_cmp(pc_right, u_left - 1) <= 0);
- qsort_assert(qsort_cmp(pc_left, pc_right) == 0);
- }
+ /* Copy all the strictly low elements */
- if (still_work_on_left) {
- /* I know I have a value on the left side which needs to be
- on the right side, but I need to know more to decide
- exactly the best thing to do with it.
- */
- if (still_work_on_right) {
- /* I know I have values on both side which are out of
- position. This is a big win because I kill two birds
- with one swap (so to speak). I can advance the
- uncompared pointers on both sides after swapping both
- of them into the right place.
- */
- qsort_swap(u_right, u_left);
- --u_right;
- ++u_left;
- qsort_all_asserts(pc_left, pc_right, u_left, u_right);
- } else {
- /* I have an out of position value on the left, but the
- right is fully scanned, so I "slide" the pivot chunk
- and any less-than values left one to make room for the
- greater value over on the right. If the out of position
- value is immediately adjacent to the pivot chunk (there
- are no less-than values), I can do that with a swap,
- otherwise, I have to rotate one of the less than values
- into the former position of the out of position value
- and the right end of the pivot chunk into the left end
- (got all that?).
- */
- --pc_left;
- if (pc_left == u_right) {
- qsort_swap(u_right, pc_right);
- qsort_all_asserts(pc_left, pc_right-1, u_left, u_right-1);
- } else {
- qsort_rotate(u_right, pc_left, pc_right);
- qsort_all_asserts(pc_left, pc_right-1, u_left, u_right-1);
- }
- --pc_right;
- --u_right;
- }
- } else if (still_work_on_right) {
- /* Mirror image of complex case above: I have an out of
- position value on the right, but the left is fully
- scanned, so I need to shuffle things around to make room
- for the right value on the left.
- */
- ++pc_right;
- if (pc_right == u_left) {
- qsort_swap(u_left, pc_left);
- qsort_all_asserts(pc_left+1, pc_right, u_left+1, u_right);
- } else {
- qsort_rotate(pc_right, pc_left, u_left);
- qsort_all_asserts(pc_left+1, pc_right, u_left+1, u_right);
- }
- ++pc_left;
- ++u_left;
- } else {
- /* No more scanning required on either side of partition,
- break out of loop and figure out next set of partitions
- */
- break;
- }
- }
-
- /* The elements in the pivot chunk are now in the right place. They
- will never move or be compared again. All I have to do is decide
- what to do with the stuff to the left and right of the pivot
- chunk.
-
- Notes on the QSORT_ORDER_GUESS ifdef code:
-
- 1. If I just built these partitions without swapping any (or
- very many) elements, there is a chance that the elements are
- already ordered properly (being properly ordered will
- certainly result in no swapping, but the converse can't be
- proved :-).
-
- 2. A (properly written) insertion sort will run faster on
- already ordered data than qsort will.
-
- 3. Perhaps there is some way to make a good guess about
- switching to an insertion sort earlier than partition size 6
- (for instance - we could save the partition size on the stack
- and increase the size each time we find we didn't swap, thus
- switching to insertion sort earlier for partitions with a
- history of not swapping).
-
- 4. Naturally, if I just switch right away, it will make
- artificial benchmarks with pure ascending (or descending)
- data look really good, but is that a good reason in general?
- Hard to say...
- */
-
-#ifdef QSORT_ORDER_GUESS
- if (swapped < 3) {
-#if QSORT_ORDER_GUESS == 1
- qsort_break_even = (part_right - part_left) + 1;
-#endif
-#if QSORT_ORDER_GUESS == 2
- qsort_break_even *= 2;
-#endif
-#if QSORT_ORDER_GUESS == 3
- int prev_break = qsort_break_even;
- qsort_break_even *= qsort_break_even;
- if (qsort_break_even < prev_break) {
- qsort_break_even = (part_right - part_left) + 1;
- }
-#endif
- } else {
- qsort_break_even = QSORT_BREAK_EVEN;
- }
-#endif
+ if (q == f1) {
+ FROMTOUPTO(f2, tp2, t);
+ *tp2++ = *f1++;
+ } else {
+ FROMTOUPTO(f1, tp2, t);
+ *tp2++ = *f2++;
+ }
+ }
- if (part_left < pc_left) {
- /* There are elements on the left which need more processing.
- Check the right as well before deciding what to do.
- */
- if (pc_right < part_right) {
- /* We have two partitions to be sorted. Stack the biggest one
- and process the smallest one on the next iteration. This
- minimizes the stack height by insuring that any additional
- stack entries must come from the smallest partition which
- (because it is smallest) will have the fewest
- opportunities to generate additional stack entries.
- */
- if ((part_right - pc_right) > (pc_left - part_left)) {
- /* stack the right partition, process the left */
- partition_stack[next_stack_entry].left = pc_right + 1;
- partition_stack[next_stack_entry].right = part_right;
-#ifdef QSORT_ORDER_GUESS
- partition_stack[next_stack_entry].qsort_break_even = qsort_break_even;
-#endif
- part_right = pc_left - 1;
- } else {
- /* stack the left partition, process the right */
- partition_stack[next_stack_entry].left = part_left;
- partition_stack[next_stack_entry].right = pc_left - 1;
-#ifdef QSORT_ORDER_GUESS
- partition_stack[next_stack_entry].qsort_break_even = qsort_break_even;
-#endif
- part_left = pc_right + 1;
- }
- qsort_assert(next_stack_entry < QSORT_MAX_STACK);
- ++next_stack_entry;
- } else {
- /* The elements on the left are the only remaining elements
- that need sorting, arrange for them to be processed as the
- next partition.
- */
- part_right = pc_left - 1;
- }
- } else if (pc_right < part_right) {
- /* There is only one chunk on the right to be sorted, make it
- the new partition and loop back around.
- */
- part_left = pc_right + 1;
- } else {
- /* This whole partition wound up in the pivot chunk, so
- we need to get a new partition off the stack.
- */
- if (next_stack_entry == 0) {
- /* the stack is empty - we are done */
- break;
- }
- --next_stack_entry;
- part_left = partition_stack[next_stack_entry].left;
- part_right = partition_stack[next_stack_entry].right;
-#ifdef QSORT_ORDER_GUESS
- qsort_break_even = partition_stack[next_stack_entry].qsort_break_even;
-#endif
- }
- } else {
- /* This partition is too small to fool with qsort complexity, just
- do an ordinary insertion sort to minimize overhead.
- */
- int i;
- /* Assume 1st element is in right place already, and start checking
- at 2nd element to see where it should be inserted.
- */
- for (i = part_left + 1; i <= part_right; ++i) {
- int j;
- /* Scan (backwards - just in case 'i' is already in right place)
- through the elements already sorted to see if the ith element
- belongs ahead of one of them.
- */
- for (j = i - 1; j >= part_left; --j) {
- if (qsort_cmp(i, j) >= 0) {
- /* i belongs right after j
- */
- break;
- }
- }
- ++j;
- if (j != i) {
- /* Looks like we really need to move some things
- */
- int k;
- temp = array[i];
- for (k = i - 1; k >= j; --k)
- array[k + 1] = array[k];
- array[j] = temp;
- }
- }
-
- /* That partition is now sorted, grab the next one, or get out
- of the loop if there aren't any more.
- */
-
- if (next_stack_entry == 0) {
- /* the stack is empty - we are done */
- break;
- }
- --next_stack_entry;
- part_left = partition_stack[next_stack_entry].left;
- part_right = partition_stack[next_stack_entry].right;
-#ifdef QSORT_ORDER_GUESS
- qsort_break_even = partition_stack[next_stack_entry].qsort_break_even;
-#endif
- }
- }
- /* Believe it or not, the array is sorted at this point! */
+ /* Run out remaining list */
+ if (f1 == l1) {
+ if (f2 < l2) FROMTOUPTO(f2, tp2, l2);
+ } else FROMTOUPTO(f1, tp2, l1);
+ p1 = NEXT(p1) = POTHER(tp2, list2, list1);
+ }
+ t = list1;
+ list1 = list2;
+ list2 = t;
+ last = PINDEX(list2, nmemb);
+ }
+ if (base == list2) {
+ last = PINDEX(list1, nmemb);
+ FROMTOUPTO(list1, list2, last);
+ }
+ Safefree(aux);
+ return;
}
projects / p5sagit/p5-mst-13.2.git / commitdiff