src/include/lib/sort_template.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * sort_template.h
   4  *
   5  *        A template for a sort algorithm that supports varying degrees of
   6  *        specialization.
   7  *
   8  * Copyright (c) 2021, PostgreSQL Global Development Group
   9  * Portions Copyright (c) 1992-1994, Regents of the University of California
  10  *
  11  * Usage notes:
  12  *
  13  *        To generate functions specialized for a type, the following parameter
  14  *        macros should be #define'd before this file is included.
  15  *
  16  *        - ST_SORT - the name of a sort function to be generated
  17  *        - ST_ELEMENT_TYPE - type of the referenced elements
  18  *        - ST_DECLARE - if defined the functions and types are declared
  19  *        - ST_DEFINE - if defined the functions and types are defined
  20  *        - ST_SCOPE - scope (e.g. extern, static inline) for functions
  21  *        - ST_CHECK_FOR_INTERRUPTS - if defined the sort is interruptible
  22  *
  23  *        Instead of ST_ELEMENT_TYPE, ST_ELEMENT_TYPE_VOID can be defined.  Then
  24  *        the generated functions will automatically gain an "element_size"
  25  *        parameter.  This allows us to generate a traditional qsort function.
  26  *
  27  *        One of the following macros must be defined, to show how to compare
  28  *        elements.  The first two options are arbitrary expressions depending
  29  *        on whether an extra pass-through argument is desired, and the third
  30  *        option should be defined if the sort function should receive a
  31  *        function pointer at runtime.
  32  *
  33  *        - ST_COMPARE(a, b) - a simple comparison expression
  34  *        - ST_COMPARE(a, b, arg) - variant that takes an extra argument
  35  *        - ST_COMPARE_RUNTIME_POINTER - sort function takes a function pointer
  36  *
  37  *        To say that the comparator and therefore also sort function should
  38  *        receive an extra pass-through argument, specify the type of the
  39  *        argument.
  40  *
  41  *        - ST_COMPARE_ARG_TYPE - type of extra argument
  42  *
  43  *        The prototype of the generated sort function is:
  44  *
  45  *        void ST_SORT(ST_ELEMENT_TYPE *data, size_t n,
  46  *                                 [size_t element_size,]
  47  *                                 [ST_SORT_compare_function compare,]
  48  *                                 [ST_COMPARE_ARG_TYPE *arg]);
  49  *
  50  *        ST_SORT_compare_function is a function pointer of the following type:
  51  *
  52  *        int (*)(const ST_ELEMENT_TYPE *a, const ST_ELEMENT_TYPE *b,
  53  *                        [ST_COMPARE_ARG_TYPE *arg])
  54  *
  55  * HISTORY
  56  *
  57  *        Modifications from vanilla NetBSD source:
  58  *        - Add do ... while() macro fix
  59  *        - Remove __inline, _DIAGASSERTs, __P
  60  *        - Remove ill-considered "swap_cnt" switch to insertion sort, in favor
  61  *              of a simple check for presorted input.
  62  *        - Take care to recurse on the smaller partition, to bound stack usage
  63  *        - Convert into a header that can generate specialized functions
  64  *
  65  * IDENTIFICATION
  66  *              src/include/lib/sort_template.h
  67  *
  68  *-------------------------------------------------------------------------
  69  */
  70
  71 /*        $NetBSD: qsort.c,v 1.13 2003/08/07 16:43:42 agc Exp $   */
  72
  73 /*-
  74  * Copyright (c) 1992, 1993
  75  *        The Regents of the University of California.  All rights reserved.
  76  *
  77  * Redistribution and use in source and binary forms, with or without
  78  * modification, are permitted provided that the following conditions
  79  * are met:
  80  * 1. Redistributions of source code must retain the above copyright
  81  *        notice, this list of conditions and the following disclaimer.
  82  * 2. Redistributions in binary form must reproduce the above copyright
  83  *        notice, this list of conditions and the following disclaimer in the
  84  *        documentation and/or other materials provided with the distribution.
  85  * 3. Neither the name of the University nor the names of its contributors
  86  *        may be used to endorse or promote products derived from this software
  87  *        without specific prior written permission.
  88  *
  89  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  90  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  91  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  92  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  93  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  94  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  95  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  96  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  97  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  98  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  99  * SUCH DAMAGE.
 100  */
 101
 102 /*
 103  * Qsort routine based on J. L. Bentley and M. D. McIlroy,
 104  * "Engineering a sort function",
 105  * Software--Practice and Experience 23 (1993) 1249-1265.
 106  *
 107  * We have modified their original by adding a check for already-sorted
 108  * input, which seems to be a win per discussions on pgsql-hackers around
 109  * 2006-03-21.
 110  *
 111  * Also, we recurse on the smaller partition and iterate on the larger one,
 112  * which ensures we cannot recurse more than log(N) levels (since the
 113  * partition recursed to is surely no more than half of the input).  Bentley
 114  * and McIlroy explicitly rejected doing this on the grounds that it's "not
 115  * worth the effort", but we have seen crashes in the field due to stack
 116  * overrun, so that judgment seems wrong.
 117  */
 118
 119 #define ST_MAKE_PREFIX(a) CppConcat(a,_)
 120 #define ST_MAKE_NAME(a,b) ST_MAKE_NAME_(ST_MAKE_PREFIX(a),b)
 121 #define ST_MAKE_NAME_(a,b) CppConcat(a,b)
 122
 123 /*
 124  * If the element type is void, we'll also need an element_size argument
 125  * because we don't know the size.
 126  */
 127 #ifdef ST_ELEMENT_TYPE_VOID
 128 #define ST_ELEMENT_TYPE void
 129 #define ST_SORT_PROTO_ELEMENT_SIZE , size_t element_size
 130 #define ST_SORT_INVOKE_ELEMENT_SIZE , element_size
 131 #else
 132 #define ST_SORT_PROTO_ELEMENT_SIZE
 133 #define ST_SORT_INVOKE_ELEMENT_SIZE
 134 #endif
 135
 136 /*
 137  * If the user wants to be able to pass in compare functions at runtime,
 138  * we'll need to make that an argument of the sort and med3 functions.
 139  */
 140 #ifdef ST_COMPARE_RUNTIME_POINTER
 141 /*
 142  * The type of the comparator function pointer that ST_SORT will take, unless
 143  * you've already declared a type name manually and want to use that instead of
 144  * having a new one defined.
 145  */
 146 #ifndef ST_COMPARATOR_TYPE_NAME
 147 #define ST_COMPARATOR_TYPE_NAME ST_MAKE_NAME(ST_SORT, compare_function)
 148 #endif
 149 #define ST_COMPARE compare
 150 #ifndef ST_COMPARE_ARG_TYPE
 151 #define ST_SORT_PROTO_COMPARE , ST_COMPARATOR_TYPE_NAME compare
 152 #define ST_SORT_INVOKE_COMPARE , compare
 153 #else
 154 #define ST_SORT_PROTO_COMPARE , ST_COMPARATOR_TYPE_NAME compare
 155 #define ST_SORT_INVOKE_COMPARE , compare
 156 #endif
 157 #else
 158 #define ST_SORT_PROTO_COMPARE
 159 #define ST_SORT_INVOKE_COMPARE
 160 #endif
 161
 162 /*
 163  * If the user wants to use a compare function or expression that takes an
 164  * extra argument, we'll need to make that an argument of the sort, compare and
 165  * med3 functions.
 166  */
 167 #ifdef ST_COMPARE_ARG_TYPE
 168 #define ST_SORT_PROTO_ARG , ST_COMPARE_ARG_TYPE *arg
 169 #define ST_SORT_INVOKE_ARG , arg
 170 #else
 171 #define ST_SORT_PROTO_ARG
 172 #define ST_SORT_INVOKE_ARG
 173 #endif
 174
 175 #ifdef ST_DECLARE
 176
 177 #ifdef ST_COMPARE_RUNTIME_POINTER
 178 typedef int (*ST_COMPARATOR_TYPE_NAME) (const ST_ELEMENT_TYPE *,
 179                                                                                 const ST_ELEMENT_TYPE * ST_SORT_PROTO_ARG);
 180 #endif
 181
 182 /* Declare the sort function.  Note optional arguments at end. */
 183 ST_SCOPE void ST_SORT(ST_ELEMENT_TYPE * first, size_t n
 184                                           ST_SORT_PROTO_ELEMENT_SIZE
 185                                           ST_SORT_PROTO_COMPARE
 186                                           ST_SORT_PROTO_ARG);
 187
 188 #endif
 189
 190 #ifdef ST_DEFINE
 191
 192 /* sort private helper functions */
 193 #define ST_MED3 ST_MAKE_NAME(ST_SORT, med3)
 194 #define ST_SWAP ST_MAKE_NAME(ST_SORT, swap)
 195 #define ST_SWAPN ST_MAKE_NAME(ST_SORT, swapn)
 196
 197 /* Users expecting to run very large sorts may need them to be interruptible. */
 198 #ifdef ST_CHECK_FOR_INTERRUPTS
 199 #define DO_CHECK_FOR_INTERRUPTS() CHECK_FOR_INTERRUPTS()
 200 #else
 201 #define DO_CHECK_FOR_INTERRUPTS()
 202 #endif
 203
 204 /*
 205  * Create wrapper macros that know how to invoke compare, med3 and sort with
 206  * the right arguments.
 207  */
 208 #ifdef ST_COMPARE_RUNTIME_POINTER
 209 #define DO_COMPARE(a_, b_) ST_COMPARE((a_), (b_) ST_SORT_INVOKE_ARG)
 210 #elif defined(ST_COMPARE_ARG_TYPE)
 211 #define DO_COMPARE(a_, b_) ST_COMPARE((a_), (b_), arg)
 212 #else
 213 #define DO_COMPARE(a_, b_) ST_COMPARE((a_), (b_))
 214 #endif
 215 #define DO_MED3(a_, b_, c_)                                                                                             \
 216         ST_MED3((a_), (b_), (c_)                                                                                        \
 217                         ST_SORT_INVOKE_COMPARE                                                                          \
 218                         ST_SORT_INVOKE_ARG)
 219 #define DO_SORT(a_, n_)                                                                                                 \
 220         ST_SORT((a_), (n_)                                                                                                      \
 221                         ST_SORT_INVOKE_ELEMENT_SIZE                                                                     \
 222                         ST_SORT_INVOKE_COMPARE                                                                          \
 223                         ST_SORT_INVOKE_ARG)
 224
 225 /*
 226  * If we're working with void pointers, we'll use pointer arithmetic based on
 227  * uint8, and use the runtime element_size to step through the array and swap
 228  * elements.  Otherwise we'll work with ST_ELEMENT_TYPE.
 229  */
 230 #ifndef ST_ELEMENT_TYPE_VOID
 231 #define ST_POINTER_TYPE ST_ELEMENT_TYPE
 232 #define ST_POINTER_STEP 1
 233 #define DO_SWAPN(a_, b_, n_) ST_SWAPN((a_), (b_), (n_))
 234 #define DO_SWAP(a_, b_) ST_SWAP((a_), (b_))
 235 #else
 236 #define ST_POINTER_TYPE uint8
 237 #define ST_POINTER_STEP element_size
 238 #define DO_SWAPN(a_, b_, n_) ST_SWAPN((a_), (b_), (n_))
 239 #define DO_SWAP(a_, b_) DO_SWAPN((a_), (b_), element_size)
 240 #endif
 241
 242 /*
 243  * Find the median of three values.  Currently, performance seems to be best
 244  * if the comparator is inlined here, but the med3 function is not inlined
 245  * in the qsort function.
 246  */
 247 static pg_noinline ST_ELEMENT_TYPE *
 248 ST_MED3(ST_ELEMENT_TYPE * a,
 249                 ST_ELEMENT_TYPE * b,
 250                 ST_ELEMENT_TYPE * c
 251                 ST_SORT_PROTO_COMPARE
 252                 ST_SORT_PROTO_ARG)
 253 {
 254         return DO_COMPARE(a, b) < 0 ?
 255                 (DO_COMPARE(b, c) < 0 ? b : (DO_COMPARE(a, c) < 0 ? c : a))
 256                 : (DO_COMPARE(b, c) > 0 ? b : (DO_COMPARE(a, c) < 0 ? a : c));
 257 }
 258
 259 static inline void
 260 ST_SWAP(ST_POINTER_TYPE * a, ST_POINTER_TYPE * b)
 261 {
 262         ST_POINTER_TYPE tmp = *a;
 263
 264         *a = *b;
 265         *b = tmp;
 266 }
 267
 268 static inline void
 269 ST_SWAPN(ST_POINTER_TYPE * a, ST_POINTER_TYPE * b, size_t n)
 270 {
 271         for (size_t i = 0; i < n; ++i)
 272                 ST_SWAP(&a[i], &b[i]);
 273 }
 274
 275 /*
 276  * Sort an array.
 277  */
 278 ST_SCOPE void
 279 ST_SORT(ST_ELEMENT_TYPE * data, size_t n
 280                 ST_SORT_PROTO_ELEMENT_SIZE
 281                 ST_SORT_PROTO_COMPARE
 282                 ST_SORT_PROTO_ARG)
 283 {
 284         ST_POINTER_TYPE *a = (ST_POINTER_TYPE *) data,
 285                            *pa,
 286                            *pb,
 287                            *pc,
 288                            *pd,
 289                            *pl,
 290                            *pm,
 291                            *pn;
 292         size_t          d1,
 293                                 d2;
 294         int                     r,
 295                                 presorted;
 296
 297 loop:
 298         DO_CHECK_FOR_INTERRUPTS();
 299         if (n < 7)
 300         {
 301                 for (pm = a + ST_POINTER_STEP; pm < a + n * ST_POINTER_STEP;
 302                          pm += ST_POINTER_STEP)
 303                         for (pl = pm; pl > a && DO_COMPARE(pl - ST_POINTER_STEP, pl) > 0;
 304                                  pl -= ST_POINTER_STEP)
 305                                 DO_SWAP(pl, pl - ST_POINTER_STEP);
 306                 return;
 307         }
 308         presorted = 1;
 309         for (pm = a + ST_POINTER_STEP; pm < a + n * ST_POINTER_STEP;
 310                  pm += ST_POINTER_STEP)
 311         {
 312                 DO_CHECK_FOR_INTERRUPTS();
 313                 if (DO_COMPARE(pm - ST_POINTER_STEP, pm) > 0)
 314                 {
 315                         presorted = 0;
 316                         break;
 317                 }
 318         }
 319         if (presorted)
 320                 return;
 321         pm = a + (n / 2) * ST_POINTER_STEP;
 322         if (n > 7)
 323         {
 324                 pl = a;
 325                 pn = a + (n - 1) * ST_POINTER_STEP;
 326                 if (n > 40)
 327                 {
 328                         size_t          d = (n / 8) * ST_POINTER_STEP;
 329
 330                         pl = DO_MED3(pl, pl + d, pl + 2 * d);
 331                         pm = DO_MED3(pm - d, pm, pm + d);
 332                         pn = DO_MED3(pn - 2 * d, pn - d, pn);
 333                 }
 334                 pm = DO_MED3(pl, pm, pn);
 335         }
 336         DO_SWAP(a, pm);
 337         pa = pb = a + ST_POINTER_STEP;
 338         pc = pd = a + (n - 1) * ST_POINTER_STEP;
 339         for (;;)
 340         {
 341                 while (pb <= pc && (r = DO_COMPARE(pb, a)) <= 0)
 342                 {
 343                         if (r == 0)
 344                         {
 345                                 DO_SWAP(pa, pb);
 346                                 pa += ST_POINTER_STEP;
 347                         }
 348                         pb += ST_POINTER_STEP;
 349                         DO_CHECK_FOR_INTERRUPTS();
 350                 }
 351                 while (pb <= pc && (r = DO_COMPARE(pc, a)) >= 0)
 352                 {
 353                         if (r == 0)
 354                         {
 355                                 DO_SWAP(pc, pd);
 356                                 pd -= ST_POINTER_STEP;
 357                         }
 358                         pc -= ST_POINTER_STEP;
 359                         DO_CHECK_FOR_INTERRUPTS();
 360                 }
 361                 if (pb > pc)
 362                         break;
 363                 DO_SWAP(pb, pc);
 364                 pb += ST_POINTER_STEP;
 365                 pc -= ST_POINTER_STEP;
 366         }
 367         pn = a + n * ST_POINTER_STEP;
 368         d1 = Min(pa - a, pb - pa);
 369         DO_SWAPN(a, pb - d1, d1);
 370         d1 = Min(pd - pc, pn - pd - ST_POINTER_STEP);
 371         DO_SWAPN(pb, pn - d1, d1);
 372         d1 = pb - pa;
 373         d2 = pd - pc;
 374         if (d1 <= d2)
 375         {
 376                 /* Recurse on left partition, then iterate on right partition */
 377                 if (d1 > ST_POINTER_STEP)
 378                         DO_SORT(a, d1 / ST_POINTER_STEP);
 379                 if (d2 > ST_POINTER_STEP)
 380                 {
 381                         /* Iterate rather than recurse to save stack space */
 382                         /* DO_SORT(pn - d2, d2 / ST_POINTER_STEP) */
 383                         a = pn - d2;
 384                         n = d2 / ST_POINTER_STEP;
 385                         goto loop;
 386                 }
 387         }
 388         else
 389         {
 390                 /* Recurse on right partition, then iterate on left partition */
 391                 if (d2 > ST_POINTER_STEP)
 392                         DO_SORT(pn - d2, d2 / ST_POINTER_STEP);
 393                 if (d1 > ST_POINTER_STEP)
 394                 {
 395                         /* Iterate rather than recurse to save stack space */
 396                         /* DO_SORT(a, d1 / ST_POINTER_STEP) */
 397                         n = d1 / ST_POINTER_STEP;
 398                         goto loop;
 399                 }
 400         }
 401 }
 402 #endif
 403
 404 #undef DO_CHECK_FOR_INTERRUPTS
 405 #undef DO_COMPARE
 406 #undef DO_MED3
 407 #undef DO_SORT
 408 #undef DO_SWAP
 409 #undef DO_SWAPN
 410 #undef ST_COMPARATOR_TYPE_NAME
 411 #undef ST_COMPARE
 412 #undef ST_COMPARE_ARG_TYPE
 413 #undef ST_COMPARE_RUNTIME_POINTER
 414 #undef ST_ELEMENT_TYPE
 415 #undef ST_ELEMENT_TYPE_VOID
 416 #undef ST_MAKE_NAME
 417 #undef ST_MAKE_NAME_
 418 #undef ST_MAKE_PREFIX
 419 #undef ST_MED3
 420 #undef ST_POINTER_STEP
 421 #undef ST_POINTER_TYPE
 422 #undef ST_SCOPE
 423 #undef ST_SORT
 424 #undef ST_SORT_INVOKE_ARG
 425 #undef ST_SORT_INVOKE_COMPARE
 426 #undef ST_SORT_INVOKE_ELEMENT_SIZE
 427 #undef ST_SORT_PROTO_ARG
 428 #undef ST_SORT_PROTO_COMPARE
 429 #undef ST_SORT_PROTO_ELEMENT_SIZE
 430 #undef ST_SWAP
 431 #undef ST_SWAPN