Replace linked-list insert-sort with merge-sort

Original code from eglib, modified for reuse with multiple linked-list implementations.

Adds sort functions: BLI_linklist_sort, BLI_linklist_sort_r

source/blender/blenlib/BLI_linklist.h

@@ -74,6 +74,8 @@ void    BLI_linklist_free(struct LinkNode *list, LinkNodeFreeFP freefunc);
 void    BLI_linklist_freeN(struct LinkNode *list);
 void    BLI_linklist_free_pool(LinkNode *list, LinkNodeFreeFP freefunc, struct BLI_mempool *mempool);
 void    BLI_linklist_apply(struct LinkNode *list, LinkNodeApplyFP applyfunc, void *userdata);
+struct LinkNode *BLI_linklist_sort(LinkNode *list, int (*cmp)(const void *, const void *));
+struct LinkNode *BLI_linklist_sort_r(LinkNode *list, int (*cmp)(void *, const void *, const void *), void *thunk);
 
 #define BLI_linklist_prepend_alloca(listp, ptr) \
 	BLI_linklist_prepend_nlink(listp, ptr, alloca(sizeof(LinkNode)))

source/blender/blenlib/CMakeLists.txt

@@ -72,6 +72,7 @@ set(SRC
 	intern/hash_mm2a.c
 	intern/jitter.c
 	intern/lasso.c
+	intern/list_sort_impl.h
 	intern/listbase.c
 	intern/math_base.c
 	intern/math_base_inline.c

source/blender/blenlib/intern/BLI_linklist.c

@@ -38,6 +38,8 @@
 #include "BLI_memarena.h"
 #include "BLI_mempool.h"
 
+#include "BLI_strict_flags.h"
+
 int BLI_linklist_length(LinkNode *list)
 {
 	int len;
@@ -308,3 +310,40 @@ void BLI_linklist_apply(LinkNode *list, LinkNodeApplyFP applyfunc, void *userdat
 	for (; list; list = list->next)
 		applyfunc(list->link, userdata);
 }
+
+/* -------------------------------------------------------------------- */
+/* Sort */
+#define SORT_IMPL_LINKTYPE LinkNode
+#define SORT_IMPL_LINKTYPE_DATA link
+
+/* regular call */
+#define SORT_IMPL_FUNC linklist_sort_fn
+#include "list_sort_impl.h"
+#undef SORT_IMPL_FUNC
+
+/* reentrant call */
+#define SORT_IMPL_USE_THUNK
+#define SORT_IMPL_FUNC linklist_sort_fn_r
+#include "list_sort_impl.h"
+#undef SORT_IMPL_FUNC
+#undef SORT_IMPL_USE_THUNK
+
+#undef SORT_IMPL_LINKTYPE
+#undef SORT_IMPL_LINKTYPE_DATA
+
+
+LinkNode *BLI_linklist_sort(LinkNode *list, int (*cmp)(const void *, const void *))
+{
+	if (list && list->next) {
+		list = linklist_sort_fn(list, cmp);
+	}
+	return list;
+}
+
+LinkNode *BLI_linklist_sort_r(LinkNode *list, int (*cmp)(void *, const void *, const void *), void *thunk)
+{
+	if (list && list->next) {
+		list = linklist_sort_fn_r(list, cmp, thunk);
+	}
+	return list;
+}

source/blender/blenlib/intern/list_sort_impl.h

@@ -0,0 +1,341 @@
+/*
+ * ***** BEGIN GPL LICENSE BLOCK *****
+ *
+ * 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ */
+
+/** \file blender/blenlib/intern/list_sort_impl.h
+ *  \ingroup bli
+ *
+ * Common implementation of linked-list a non-recursive mergesort.
+ *
+ * Originally from Mono's eglib, adapted for portable inclusion.
+ * This file is to be directly included in C-source,
+ * with defines to control its use.
+ *
+ * This code requires a typedef named `SORT_IMPL_LINKTYPE` for the list node.
+ * It is assumed that the list type is the type of a pointer to a list
+ * node, and that the node has a field named 'next' that implements to
+ * the linked list.  No additional invariant is maintained
+ * (e.g. the `prev` pointer of a doubly-linked list node is _not_ updated).
+ * Any invariant would require a post-processing pass to update `prev`.
+ *
+ * Source file including this must define:
+ * - `SORT_IMPL_LINKTYPE`:
+ *   Struct type for sorting.
+ * - `SORT_IMPL_LINKTYPE_DATA`:
+ *   Data pointer or leave undefined to pass the link its self.
+ * - `SORT_IMPL_FUNC`:
+ *   Function name of the sort function.
+ *
+ * Optionally:
+ * - `SORT_IMPL_USE_THUNK`:
+ *   Takes an argument for the sort function (like `qsort_r`).
+ */
+
+/* -------------------------------------------------------------------- */
+/* Handle External Defines */
+
+/* check we're not building directly */
+#if !defined(SORT_IMPL_LINKTYPE) || !defined(SORT_IMPL_FUNC)
+#  error "This file can't be compiled directly, include in another source file"
+#endif
+
+#define list_node SORT_IMPL_LINKTYPE
+#define list_sort_do SORT_IMPL_FUNC
+
+#ifdef SORT_IMPL_LINKTYPE_DATA
+#  define SORT_ARG(n) ((n)->SORT_IMPL_LINKTYPE_DATA)
+#else
+#  define SORT_ARG(n) (n)
+#endif
+
+#ifdef SORT_IMPL_USE_THUNK
+#  define THUNK_APPEND1(a, thunk) a, thunk
+#  define THUNK_PREPEND2(thunk, a, b) thunk, a, b
+#else
+#  define THUNK_APPEND1(a, thunk) a
+#  define THUNK_PREPEND2(thunk, a, b) a, b
+#endif
+
+#define _CONCAT_AUX(MACRO_ARG1, MACRO_ARG2) MACRO_ARG1 ## MACRO_ARG2
+#define _CONCAT(MACRO_ARG1, MACRO_ARG2) _CONCAT_AUX(MACRO_ARG1, MACRO_ARG2)
+#define _SORT_PREFIX(id) _CONCAT(SORT_IMPL_FUNC, _##id)
+
+/* local identifiers */
+#define SortInfo		_SORT_PREFIX(SortInfo)
+#define CompareFn		_SORT_PREFIX(CompareFn)
+#define init_sort_info	_SORT_PREFIX(init_sort_info)
+#define merge_lists		_SORT_PREFIX(merge_lists)
+#define sweep_up		_SORT_PREFIX(sweep_up)
+#define insert_list		_SORT_PREFIX(insert_list)
+
+typedef int (* CompareFn)(
+#ifdef SORT_IMPL_USE_THUNK
+        void *thunk,
+#endif
+        const void *,
+        const void *);
+
+
+/* -------------------------------------------------------------------- */
+/* MIT license from original source */
+
+/*
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Author:
+ *   Raja R Harinath (rharinath@novell.com)
+ */
+
+/**
+ * The maximum possible depth of the merge tree
+ * - `ceiling(log2(maximum number of list nodes))`
+ * - `ceiling(log2(maximum possible memory size/size of each list node))`
+ * - number of bits in `'size_t' - floor(log2(sizeof(list_node *)))`
+ *
+ * Also, each list in #SortInfo is at least 2 nodes long:
+ * we can reduce the depth by 1.
+ */
+#define FLOOR_LOG2(x) \
+	(((x) >= 2) + ((x) >= 4) + ((x) >= 8) + ((x) >= 16) + ((x) >= 32) + ((x) >= 64) + ((x) >= 128))
+#define MAX_RANKS \
+	((sizeof(size_t) * 8) - FLOOR_LOG2(sizeof(list_node)) - 1)
+
+struct SortInfo {
+	unsigned int min_rank, n_ranks;
+	CompareFn func;
+
+#ifdef SORT_IMPL_USE_THUNK
+	void *thunk;
+#endif
+
+	/**
+	 * Invariant: `ranks[i] == NULL || length(ranks[i]) >= 2**(i+1)`.
+	 *
+	 * ~ 128 bytes on 32bit, ~ 512 bytes on 64bit */
+	list_node *ranks[MAX_RANKS];
+};
+
+BLI_INLINE void init_sort_info(
+        struct SortInfo *si,
+        CompareFn func
+#ifdef SORT_IMPL_USE_THUNK
+        ,
+        void *thunk
+#endif
+        )
+{
+	si->min_rank = si->n_ranks = 0;
+	si->func = func;
+	/* we don't need to initialize si->ranks,
+	 * since we never lookup past si->n_ranks. */
+
+#ifdef SORT_IMPL_USE_THUNK
+	si->thunk = thunk;
+#endif
+}
+
+BLI_INLINE list_node *merge_lists(
+        list_node *first, list_node *second,
+        CompareFn func
+#ifdef SORT_IMPL_USE_THUNK
+        ,
+        void *thunk
+#endif
+        )
+{
+	/* merge the two lists */
+	list_node *list = NULL;
+	list_node **pos = &list;
+	while (first && second) {
+		if (func(THUNK_PREPEND2(thunk, SORT_ARG(first), SORT_ARG(second))) > 0) {
+			*pos = second;
+			second = second->next;
+		}
+		else {
+			*pos = first;
+			first = first->next;
+		}
+		pos = &((*pos)->next);
+	}
+	*pos = first ? first : second;
+	return list;
+}
+
+/**
+ * Pre-condition:
+ * `upto <= si->n_ranks, list == NULL || length(list) == 1`
+ */
+BLI_INLINE list_node *sweep_up(struct SortInfo *si, list_node *list, unsigned int upto)
+{
+	unsigned int i;
+	for (i = si->min_rank; i < upto; i++) {
+		list = merge_lists(si->ranks[i], list, THUNK_APPEND1(si->func, si->thunk));
+		si->ranks[i] = NULL;
+	}
+	return list;
+}
+
+/**
+ * The 'ranks' array essentially captures the recursion stack of a mergesort.
+ * The merge tree is built in a bottom-up manner.  The control loop for
+ * updating the 'ranks' array is analogous to incrementing a binary integer,
+ * and the `O(n)` time for counting upto n translates to `O(n)` merges when
+ * inserting `rank-0` lists.
+ * When we plug in the sizes of the lists involved in those merges,
+ * we get the `O(n log n)` time for the sort.
+ *
+ * Inserting higher-ranked lists reduce the height of the merge tree,
+ * and also eliminate a lot of redundant comparisons when merging two lists
+ * that would've been part of the same run.
+ * Adding a `rank-i` list is analogous to incrementing a binary integer by
+ * `2**i` in one operation, thus sharing a similar speedup.
+ *
+ * When inserting higher-ranked lists, we choose to clear out the lower ranks
+ * in the interests of keeping the sort stable, but this makes analysis harder.
+ * Note that clearing the lower-ranked lists is `O(length(list))--` thus it
+ * shouldn't affect the `O(n log n)` behaviour.
+ * In other words, inserting one `rank-i` list is equivalent to inserting
+ * `2**i` `rank-0` lists, thus even if we do `i` additional merges
+ * in the clearing-out (taking at most `2**i` time) we are still fine.
+ */
+
+/**
+ * Pre-condition:
+ * `2**(rank+1) <= length(list) < 2**(rank+2)`
+ * (therefore: `length(list) >= 2`)
+ */
+BLI_INLINE void insert_list(
+        struct SortInfo *si,
+        list_node *list,
+        unsigned int rank)
+{
+	unsigned int i;
+
+	if (rank > si->n_ranks) {
+		if (UNLIKELY(rank > MAX_RANKS)) {
+			// printf("Rank '%d' should not exceed " STRINGIFY(MAX_RANKS), rank);
+			rank = MAX_RANKS;
+		}
+		list = merge_lists(sweep_up(si, NULL, si->n_ranks), list, THUNK_APPEND1(si->func, si->thunk));
+		for (i = si->n_ranks; i < rank; ++i) {
+			si->ranks[i] = NULL;
+		}
+	}
+	else {
+		if (rank) {
+			list = merge_lists(sweep_up(si, NULL, rank), list, THUNK_APPEND1(si->func, si->thunk));
+		}
+		for (i = rank; i < si->n_ranks && si->ranks[i]; ++i) {
+			list = merge_lists(si->ranks[i], list, THUNK_APPEND1(si->func, si->thunk));
+			si->ranks[i] = NULL;
+		}
+	}
+
+	/* Will _never_ happen: so we can just devolve into quadratic ;-) */
+	if (UNLIKELY(i == MAX_RANKS)) {
+		i--;
+	}
+
+	if (i >= si->n_ranks) {
+		si->n_ranks = i + 1;
+	}
+
+	si->min_rank = i;
+	si->ranks[i] = list;
+}
+
+#undef MAX_RANKS
+#undef FLOOR_LOG2
+
+/**
+ * Main sort function.
+ */
+BLI_INLINE list_node *list_sort_do(
+        list_node *list,
+        CompareFn func
+#ifdef SORT_IMPL_USE_THUNK
+        ,
+        void *thunk
+#endif
+        )
+{
+	struct SortInfo si;
+
+	init_sort_info(
+	        &si,
+	        func
+#ifdef SORT_IMPL_USE_THUNK
+	        ,
+	        thunk
+#endif
+	        );
+
+	while (list && list->next) {
+		list_node *next = list->next;
+		list_node *tail = next->next;
+
+		if (func(THUNK_PREPEND2(thunk, SORT_ARG(list), SORT_ARG(next))) > 0) {
+			next->next = list;
+			next = list;
+			list = list->next;
+		}
+		next->next = NULL;
+
+		insert_list(&si, list, 0);
+
+		list = tail;
+	}
+
+	return sweep_up(&si, list, si.n_ranks);
+}
+
+#undef _CONCAT_AUX
+#undef _CONCAT
+#undef _SORT_PREFIX
+
+#undef SortInfo
+#undef CompareFn
+#undef init_sort_info
+#undef merge_lists
+#undef sweep_up
+#undef insert_list
+
+#undef list_node
+#undef list_sort_do
+
+#undef THUNK_APPEND1
+#undef THUNK_PREPEND2
+#undef SORT_ARG

source/blender/blenlib/intern/listbase.c

@@ -42,6 +42,8 @@
 
 #include "BLI_listbase.h"
 
+#include "BLI_strict_flags.h"
+
 /* implementation */
 
 /**
@@ -205,6 +207,35 @@ void BLI_freelinkN(ListBase *listbase, void *vlink)
 	MEM_freeN(link);
 }
 
+/**
+ * Assigns all #Link.prev pointers from #Link.next
+ */
+static void listbase_double_from_single(Link *iter, ListBase *listbase)
+{
+	Link *prev = NULL;
+	listbase->first = iter;
+	do {
+		iter->prev = prev;
+		prev = iter;
+	} while ((iter = iter->next));
+	listbase->last = prev;
+}
+
+#define SORT_IMPL_LINKTYPE Link
+
+/* regular call */
+#define SORT_IMPL_FUNC listbase_sort_fn
+#include "list_sort_impl.h"
+#undef SORT_IMPL_FUNC
+
+/* reentrant call */
+#define SORT_IMPL_USE_THUNK
+#define SORT_IMPL_FUNC listbase_sort_fn_r
+#include "list_sort_impl.h"
+#undef SORT_IMPL_FUNC
+#undef SORT_IMPL_USE_THUNK
+
+#undef SORT_IMPL_LINKTYPE
 
 /**
  * Sorts the elements of listbase into the order defined by cmp
@@ -213,45 +244,19 @@ void BLI_freelinkN(ListBase *listbase, void *vlink)
  */
 void BLI_listbase_sort(ListBase *listbase, int (*cmp)(const void *, const void *))
 {
-	Link *current = NULL;
-	Link *previous = NULL;
-	Link *next = NULL;
-
 	if (listbase->first != listbase->last) {
-		for (previous = listbase->first, current = previous->next; current; current = next) {
-			next = current->next;
-			previous = current->prev;
-			
-			BLI_remlink(listbase, current);
-			
-			while (previous && cmp(previous, current) == 1) {
-				previous = previous->prev;
-			}
-			
-			BLI_insertlinkafter(listbase, previous, current);
-		}
+		Link *head = listbase->first;
+		head = listbase_sort_fn(head, cmp);
+		listbase_double_from_single(head, listbase);
 	}
 }
 
 void BLI_listbase_sort_r(ListBase *listbase, int (*cmp)(void *, const void *, const void *), void *thunk)
 {
-	Link *current = NULL;
-	Link *previous = NULL;
-	Link *next = NULL;
-
 	if (listbase->first != listbase->last) {
-		for (previous = listbase->first, current = previous->next; current; current = next) {
-			next = current->next;
-			previous = current->prev;
-
-			BLI_remlink(listbase, current);
-
-			while (previous && cmp(thunk, previous, current) == 1) {
-				previous = previous->prev;
-			}
-
-			BLI_insertlinkafter(listbase, previous, current);
-		}
+		Link *head = listbase->first;
+		head = listbase_sort_fn_r(head, cmp, thunk);
+		listbase_double_from_single(head, listbase);
 	}
 }