Add glibc's sorts

Also rename musl's sort function for more consistency.

6 files changed, 566 insertions, 4 deletions

diff --git a/bench.c b/bench.c
index fb46b94..a51ee99 100644
--- a/bench.c
+++ b/bench.c
@@ -28,7 +28,7 @@ static int compare(const void *a, const void *b)
 
 #define CMP_WIDTH  12
 #define MS_WIDTH   6
-#define SORT_WIDTH 10
+#define SORT_WIDTH 16
 #define GEN_WIDTH  (CMP_WIDTH + MS_WIDTH + 1)
 #define SIZE_WIDTH 10
 
diff --git a/glibc_msort.c b/glibc_msort.c
new file mode 100644
index 0000000..e35f477
--- /dev/null
+++ b/glibc_msort.c
@@ -0,0 +1,309 @@
+/* An alternative to qsort, with an identical interface.
+   This file is part of the GNU C Library.
+   Copyright (C) 1992-2014 Free Software Foundation, Inc.
+   Written by Mike Haertel, September 1988.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* minor modifications made to compile in the qsort_bench tree rather than the glibc tree */
+
+#include <alloca.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+
+#include "sorters.h"
+
+#define __alloca(n)            alloca(n)
+#define __sysconf(n)           sysconf(n)
+#define atomic_write_barrier() do {              } while(0)
+#define __set_errno(e)         do { errno = (e); } while(0)
+
+static inline void *__mempcpy(void * restrict dest, const void * restrict src, size_t n)
+{
+	memcpy(dest, src, n);
+	return ((char *) dest) + n;
+}
+
+struct msort_param
+{
+  size_t s;
+  size_t var;
+  cmpfun cmp;
+  char *t;
+};
+
+static void
+msort_with_tmp (const struct msort_param *p, void *b, size_t n)
+{
+  char *b1, *b2;
+  size_t n1, n2;
+
+  if (n <= 1)
+    return;
+
+  n1 = n / 2;
+  n2 = n - n1;
+  b1 = b;
+  b2 = (char *) b + (n1 * p->s);
+
+  msort_with_tmp (p, b1, n1);
+  msort_with_tmp (p, b2, n2);
+
+  char *tmp = p->t;
+  const size_t s = p->s;
+  cmpfun cmp = p->cmp;
+  switch (p->var)
+    {
+    case 0:
+      while (n1 > 0 && n2 > 0)
+	{
+	  if ((*cmp) (b1, b2) <= 0)
+	    {
+	      *(uint32_t *) tmp = *(uint32_t *) b1;
+	      b1 += sizeof (uint32_t);
+	      --n1;
+	    }
+	  else
+	    {
+	      *(uint32_t *) tmp = *(uint32_t *) b2;
+	      b2 += sizeof (uint32_t);
+	      --n2;
+	    }
+	  tmp += sizeof (uint32_t);
+	}
+      break;
+    case 1:
+      while (n1 > 0 && n2 > 0)
+	{
+	  if ((*cmp) (b1, b2) <= 0)
+	    {
+	      *(uint64_t *) tmp = *(uint64_t *) b1;
+	      b1 += sizeof (uint64_t);
+	      --n1;
+	    }
+	  else
+	    {
+	      *(uint64_t *) tmp = *(uint64_t *) b2;
+	      b2 += sizeof (uint64_t);
+	      --n2;
+	    }
+	  tmp += sizeof (uint64_t);
+	}
+      break;
+    case 2:
+      while (n1 > 0 && n2 > 0)
+	{
+	  unsigned long *tmpl = (unsigned long *) tmp;
+	  unsigned long *bl;
+
+	  tmp += s;
+	  if ((*cmp) (b1, b2) <= 0)
+	    {
+	      bl = (unsigned long *) b1;
+	      b1 += s;
+	      --n1;
+	    }
+	  else
+	    {
+	      bl = (unsigned long *) b2;
+	      b2 += s;
+	      --n2;
+	    }
+	  while (tmpl < (unsigned long *) tmp)
+	    *tmpl++ = *bl++;
+	}
+      break;
+    case 3:
+      while (n1 > 0 && n2 > 0)
+	{
+	  if ((*cmp) (*(const void **) b1, *(const void **) b2) <= 0)
+	    {
+	      *(void **) tmp = *(void **) b1;
+	      b1 += sizeof (void *);
+	      --n1;
+	    }
+	  else
+	    {
+	      *(void **) tmp = *(void **) b2;
+	      b2 += sizeof (void *);
+	      --n2;
+	    }
+	  tmp += sizeof (void *);
+	}
+      break;
+    default:
+      while (n1 > 0 && n2 > 0)
+	{
+	  if ((*cmp) (b1, b2) <= 0)
+	    {
+	      tmp = (char *) __mempcpy (tmp, b1, s);
+	      b1 += s;
+	      --n1;
+	    }
+	  else
+	    {
+	      tmp = (char *) __mempcpy (tmp, b2, s);
+	      b2 += s;
+	      --n2;
+	    }
+	}
+      break;
+    }
+
+  if (n1 > 0)
+    memcpy (tmp, b1, n1 * s);
+  memcpy (b, p->t, (n - n2) * s);
+}
+
+
+void
+glibc_mergesort (void *b, size_t n, size_t s, cmpfun cmp)
+{
+  size_t size = n * s;
+  char *tmp = NULL;
+  struct msort_param p;
+
+  /* For large object sizes use indirect sorting.  */
+  if (s > 32)
+    size = 2 * n * sizeof (void *) + s;
+
+  if (size < 1024)
+    /* The temporary array is small, so put it on the stack.  */
+    p.t = __alloca (size);
+  else
+    {
+      /* We should avoid allocating too much memory since this might
+	 have to be backed up by swap space.  */
+      static long int phys_pages;
+      static int pagesize;
+
+      if (pagesize == 0)
+	{
+	  phys_pages = __sysconf (_SC_PHYS_PAGES);
+
+	  if (phys_pages == -1)
+	    /* Error while determining the memory size.  So let's
+	       assume there is enough memory.  Otherwise the
+	       implementer should provide a complete implementation of
+	       the `sysconf' function.  */
+	    phys_pages = (long int) (~0ul >> 1);
+
+	  /* The following determines that we will never use more than
+	     a quarter of the physical memory.  */
+	  phys_pages /= 4;
+
+	  /* Make sure phys_pages is written to memory.  */
+	  atomic_write_barrier ();
+
+	  pagesize = __sysconf (_SC_PAGESIZE);
+	}
+
+      /* Just a comment here.  We cannot compute
+	   phys_pages * pagesize
+	   and compare the needed amount of memory against this value.
+	   The problem is that some systems might have more physical
+	   memory then can be represented with a `size_t' value (when
+	   measured in bytes.  */
+
+      /* If the memory requirements are too high don't allocate memory.  */
+      if (size / pagesize > (size_t) phys_pages)
+	{
+	  glibc_quicksort (b, n, s, cmp);
+	  return;
+	}
+
+      /* It's somewhat large, so malloc it.  */
+      int save = errno;
+      tmp = malloc (size);
+      __set_errno (save);
+      if (tmp == NULL)
+	{
+	  /* Couldn't get space, so use the slower algorithm
+	     that doesn't need a temporary array.  */
+	  glibc_quicksort (b, n, s, cmp);
+	  return;
+	}
+      p.t = tmp;
+    }
+
+  p.s = s;
+  p.var = 4;
+  p.cmp = cmp;
+
+  if (s > 32)
+    {
+      /* Indirect sorting.  */
+      char *ip = (char *) b;
+      void **tp = (void **) (p.t + n * sizeof (void *));
+      void **t = tp;
+      void *tmp_storage = (void *) (tp + n);
+
+      while ((void *) t < tmp_storage)
+	{
+	  *t++ = ip;
+	  ip += s;
+	}
+      p.s = sizeof (void *);
+      p.var = 3;
+      msort_with_tmp (&p, p.t + n * sizeof (void *), n);
+
+      /* tp[0] .. tp[n - 1] is now sorted, copy around entries of
+	 the original array.  Knuth vol. 3 (2nd ed.) exercise 5.2-10.  */
+      char *kp;
+      size_t i;
+      for (i = 0, ip = (char *) b; i < n; i++, ip += s)
+	if ((kp = tp[i]) != ip)
+	  {
+	    size_t j = i;
+	    char *jp = ip;
+	    memcpy (tmp_storage, ip, s);
+
+	    do
+	      {
+		size_t k = (kp - (char *) b) / s;
+		tp[j] = jp;
+		memcpy (jp, kp, s);
+		j = k;
+		jp = kp;
+		kp = tp[k];
+	      }
+	    while (kp != ip);
+
+	    tp[j] = jp;
+	    memcpy (jp, tmp_storage, s);
+	  }
+    }
+  else
+    {
+      if ((s & (sizeof (uint32_t) - 1)) == 0
+	  && ((char *) b - (char *) 0) % __alignof__ (uint32_t) == 0)
+	{
+	  if (s == sizeof (uint32_t))
+	    p.var = 0;
+	  else if (s == sizeof (uint64_t)
+		   && ((char *) b - (char *) 0) % __alignof__ (uint64_t) == 0)
+	    p.var = 1;
+	  else if ((s & (sizeof (unsigned long) - 1)) == 0
+		   && ((char *) b - (char *) 0)
+		      % __alignof__ (unsigned long) == 0)
+	    p.var = 2;
+	}
+      msort_with_tmp (&p, b, n);
+    }
+  free (tmp);
+}
diff --git a/glibc_qsort.c b/glibc_qsort.c
new file mode 100644
index 0000000..ed7baf7
--- /dev/null
+++ b/glibc_qsort.c
@@ -0,0 +1,249 @@
+/* Copyright (C) 1991-2014 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Written by Douglas C. Schmidt (schmidt@ics.uci.edu).
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+/* If you consider tuning this algorithm, you should consult first:
+   Engineering a sort function; Jon Bentley and M. Douglas McIlroy;
+   Software - Practice and Experience; Vol. 23 (11), 1249-1265, 1993.  */
+
+#include <limits.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "sorters.h"
+
+/* Byte-wise swap two items of size SIZE. */
+#define SWAP(a, b, size)						      \
+  do									      \
+    {									      \
+      size_t __size = (size);						      \
+      char *__a = (a), *__b = (b);					      \
+      do								      \
+	{								      \
+	  char __tmp = *__a;						      \
+	  *__a++ = *__b;						      \
+	  *__b++ = __tmp;						      \
+	} while (--__size > 0);						      \
+    } while (0)
+
+/* 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;
+
+/* The next 4 #defines implement a very fast in-line stack abstraction. */
+/* The stack needs log (total_elements) entries (we could even subtract
+   log(MAX_THRESH)).  Since total_elements has type size_t, we get as
+   upper bound for log (total_elements):
+   bits per byte (CHAR_BIT) * sizeof(size_t).  */
+#define STACK_SIZE	(CHAR_BIT * sizeof(size_t))
+#define PUSH(low, high)	((void) ((top->lo = (low)), (top->hi = (high)), ++top))
+#define	POP(low, high)	((void) (--top, (low = top->lo), (high = top->hi)))
+#define	STACK_NOT_EMPTY	(stack < top)
+
+
+/* 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 SIZE_MAX is allocated on the
+      stack.  Assuming a 32-bit (64 bit) integer for size_t, this needs
+      only 32 * sizeof(stack_node) == 256 bytes (for 64 bit: 1024 bytes).
+      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 (total_elems)
+      stack size is needed (actually O(1) in this case)!  */
+
+void
+glibc_quicksort (void *pbase, size_t total_elems, size_t size, cmpfun cmp)
+{
+  char *base_ptr = (char *) pbase;
+
+  const size_t max_thresh = MAX_THRESH * size;
+
+  if (total_elems == 0)
+    /* Avoid lossage with unsigned arithmetic below.  */
+    return;
+
+  if (total_elems > MAX_THRESH)
+    {
+      char *lo = base_ptr;
+      char *hi = &lo[size * (total_elems - 1)];
+      stack_node stack[STACK_SIZE];
+      stack_node *top = stack;
+
+      PUSH (NULL, NULL);
+
+      while (STACK_NOT_EMPTY)
+        {
+          char *left_ptr;
+          char *right_ptr;
+
+	  /* 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 in
+	     the while loops. */
+
+	  char *mid = lo + size * ((hi - lo) / size >> 1);
+
+	  if ((*cmp) ((void *) mid, (void *) lo) < 0)
+	    SWAP (mid, lo, size);
+	  if ((*cmp) ((void *) hi, (void *) mid) < 0)
+	    SWAP (mid, hi, size);
+	  else
+	    goto jump_over;
+	  if ((*cmp) ((void *) mid, (void *) lo) < 0)
+	    SWAP (mid, lo, size);
+	jump_over:;
+
+	  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) ((void *) left_ptr, (void *) mid) < 0)
+		left_ptr += size;
+
+	      while ((*cmp) ((void *) mid, (void *) right_ptr) < 0)
+		right_ptr -= size;
+
+	      if (left_ptr < right_ptr)
+		{
+		  SWAP (left_ptr, right_ptr, size);
+		  if (mid == left_ptr)
+		    mid = right_ptr;
+		  else if (mid == right_ptr)
+		    mid = left_ptr;
+		  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 ((size_t) (right_ptr - lo) <= max_thresh)
+            {
+              if ((size_t) (hi - left_ptr) <= max_thresh)
+		/* Ignore both small partitions. */
+                POP (lo, hi);
+              else
+		/* Ignore small left partition. */
+                lo = left_ptr;
+            }
+          else if ((size_t) (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 *const end_ptr = &base_ptr[size * (total_elems - 1)];
+    char *tmp_ptr = base_ptr;
+    char *thresh = min(end_ptr, base_ptr + max_thresh);
+    char *run_ptr;
+
+    /* 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) ((void *) run_ptr, (void *) 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.  */
+
+    run_ptr = base_ptr + size;
+    while ((run_ptr += size) <= end_ptr)
+      {
+	tmp_ptr = run_ptr - size;
+	while ((*cmp) ((void *) run_ptr, (void *) tmp_ptr) < 0)
+	  tmp_ptr -= size;
+
+	tmp_ptr += size;
+        if (tmp_ptr != run_ptr)
+          {
+            char *trav;
+
+	    trav = run_ptr + size;
+	    while (--trav >= run_ptr)
+              {
+                char c = *trav;
+                char *hi, *lo;
+
+                for (hi = lo = trav; (lo -= size) >= tmp_ptr; hi = lo)
+                  *hi = *lo;
+                *hi = c;
+              }
+          }
+      }
+  }
+}
diff --git a/musl_qsort.c b/musl_qsort.c
index 21a39bd..3792aa1 100644
--- a/musl_qsort.c
+++ b/musl_qsort.c
@@ -154,7 +154,7 @@ static void trinkle(unsigned char *head, size_t width, cmpfun cmp, size_t pp[2],
 	}
 }
 
-void qsort_musl(void *base, size_t nel, size_t width, cmpfun cmp)
+void musl_qsort(void *base, size_t nel, size_t width, cmpfun cmp)
 {
 	size_t lp[12*sizeof(size_t)];
 	size_t i, size = width * nel;
diff --git a/sorters.c b/sorters.c
index a630136..5150272 100644
--- a/sorters.c
+++ b/sorters.c
@@ -1,6 +1,8 @@
 #include "sorters.h"
 
 const struct sorter sorters[] = {
-	{ .name = "musl", .func = qsort_musl },
+	{ .name = "glibc quicksort", .func = glibc_quicksort },
+	{ .name = "glibc mergesort", .func = glibc_mergesort },
+	{ .name = "musl",            .func = musl_qsort      },
 	{ 0 }
 };
diff --git a/sorters.h b/sorters.h
index 1a2397a..c6850d2 100644
--- a/sorters.h
+++ b/sorters.h
@@ -3,7 +3,9 @@
 typedef int  (*cmpfun)(const void *, const void *);
 typedef void (*sorter)(void *, size_t, size_t, cmpfun);
 
-void qsort_musl(void *, size_t, size_t, cmpfun);
+void musl_qsort(void *, size_t, size_t, cmpfun);
+void glibc_quicksort(void *, size_t, size_t, cmpfun);
+void glibc_mergesort(void *, size_t, size_t, cmpfun);
 
 extern const struct sorter {
 	const char *name;