1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474
|
/* $Id$
Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: jan@swi.psy.uva.nl
WWW: http://www.swi-prolog.org
Copyright (C): 1985-2002, University of Amsterdam
This 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.
This 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 this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "pl-incl.h"
#undef LD
#define LD LOCAL_LD
static
PRED_IMPL("is_list", 1, is_list, 0)
{ if ( lengthList(A1, FALSE) >= 0 )
succeed;
fail;
}
/** $length(-List, +Len) is semidet.
Implements `known-length' generation path of length/2. Fails if Len < 0.
*/
static
PRED_IMPL("$length", 2, dlength, 0)
{ PRED_LD
intptr_t len;
if ( PL_get_intptr(A2, &len) )
{ if ( len > 0 )
{ Word p;
term_t list = PL_new_term_ref();
if ( !hasGlobalSpace(len*3) )
{ int rc;
if ( (rc=ensureGlobalSpace(len*3, ALLOW_GC)) != TRUE )
return raiseStackOverflow(rc);
}
p = gTop;
*valTermRef(list) = consPtr(p, TAG_COMPOUND|STG_GLOBAL);
while(len-- > 0)
{ p[0] = FUNCTOR_dot2;
setVar(p[1]);
p[2] = consPtr(&p[3], TAG_COMPOUND|STG_GLOBAL);
p += 3;
}
p[-1] = ATOM_nil;
gTop = p;
return PL_unify(A1, list);
} else if ( len == 0 )
{ return PL_unify_nil(A1);
} else
{ return FALSE;
}
} else if ( PL_is_integer(A2) )
{ number i;
Word p = valTermRef(A2);
deRef(p);
get_integer(*p, &i);
if ( ar_sign_i(&i) < 0 )
return FALSE;
return outOfStack((Stack)&LD->stacks.global, STACK_OVERFLOW_RAISE);
}
return PL_error("length", 2, NULL, ERR_TYPE, ATOM_integer, A2);
}
static
PRED_IMPL("memberchk", 2, memberchk, 0)
{ GET_LD
term_t h = PL_new_term_ref();
term_t l = PL_copy_term_ref(A2);
fid_t fid;
if ( !(fid=PL_open_foreign_frame()) )
return FALSE;
for(;;)
{ if ( !PL_unify_list(l, h, l) )
{ PL_close_foreign_frame(fid);
PL_unify_nil_ex(l);
return FALSE;
}
if ( PL_unify(A1, h) )
{ term_t ex = 0;
if ( foreignWakeup(&ex PASS_LD) )
{ PL_close_foreign_frame(fid);
succeed;
} else
{ if ( ex )
return PL_raise_exception(ex);
PL_rewind_foreign_frame(fid);
}
} else
{ PL_rewind_foreign_frame(fid);
}
}
}
/*******************************
* SORTING *
*******************************/
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Natural merge sort. Code contributed by Richard O'Keefe and integrated
into SWI-Prolog by Jan Wielemaker. The nice point about this code is
that it uses no extra space and is pretty stable in performance.
Richards claim it that many qsort() implementations in libc are very
slow. This isn't the case for glibc 2.2, where this performs about the
same as the previous qsort() based implementation. However, it
integrated keysort/2 in the set and here the difference is huge.
Here is C code implementing a bottom-up natural merge sort on lists; it
has remove_dups and compare_keys options. (Actually I wouldn't handle
the compare_keys option quite like this.) The difference between this
and sam-sort is the way runs are built:
natural merge:
add new node r after last node q of run if item(q) <= item(r)
otherwise end this run.
sam-sort:
add new node r after last node q of run if item(q) <= item(r)
otherwise
add new new r before first node p of run if item(r) < item(p)
otherwise end this run.
The natural merge has the nice property that if the list is already
sorted it takes O(N) time. In general if you have a list made of M
already sorted pieces S1++S2++...++SM it will take no more than O(N.log
M). Sam-sort (for "Smooth Applicative Merge sort") has the nice property
that it likes the reverse order almost as much as forward order, so \ /\
and \/ patterns are sorted (nearly) as fast as / // and // patterns
respectively.
I've been using a variant of this code in a sorting utility since about
1988. It leaves the UNIX sort(1) program in the dust. As you may know,
sort(1) breaks the input into blocks that fit in memory, sorts the
blocks using qsort(), and writes the blocks out to disc, then merges the
blocks. For files that fit into memory, the variant of this code runs
about twice as fast as sort(1). Part of that is better I/O, but part is
just plain not using qsort().
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
/* Things in capital letters should be replaced for different applications */
/* ITEM The type of an individual item.
COMPARE Compares two items given their addresses (allows ITEM to be
large and avoids pass by copy). Return <0, =0, or >0.
COMPARE_KEY Compares the keys of two items given the addresses of the
entire items.
FREE Frees a List_Record including its ITEM.
*/
typedef struct
{ Word term;
Word key;
} ITEM;
/* TBD: handle CMP_ERROR */
#ifndef COMPARE
#define COMPARE(x,y) compareStandard((x)->term, (y)->term, FALSE PASS_LD)
#endif
#ifndef COMPARE_KEY
#define COMPARE_KEY(x,y) compareStandard((x)->key, (y)->key, FALSE PASS_LD)
#endif
#ifndef FREE
#define FREE(x) \
{ x->next = NULL; \
x->item.term = NULL; \
x->item.key = NULL; \
}
#endif
typedef struct List_Record *list;
struct List_Record {
list next;
ITEM item;
};
#define NIL (list)0
#define compare(c, x, y) \
int c = compare_keys ? COMPARE_KEY(&(x)->item, &(y)->item) \
: COMPARE( &(x)->item, &(y)->item)
static list
nat_sort(list data, int remove_dups, int compare_keys)
{ GET_LD
list stack[64]; /* enough for biggest machine */
list *sp = stack;
int runs = 0; /* total number of runs processed */
list p, q, r, s;
struct List_Record header;
int k;
remove_dups = !remove_dups; /* 0 -> do, 1 -> don't */
while ((p = data) != NIL)
{ /* pick up a run from the front of data, setting */
/* p = (pointer to beginning of run), data = (rest of data) */
if ((q = p->next) != NIL)
{ compare(c, p, q);
data = q->next;
if (c > 0)
{ r = q, q = p, p = r;
p->next = q;
} else if (c == remove_dups)
{ /* c < 0 or = 0, so c = 1 impossible */
p->next = q->next;
FREE(q);
q = p;
}
for (r = data; r != NIL; )
{ compare(c, q, r);
if (c > 0)
break;
if (c == remove_dups)
{ s = r->next;
FREE(r);
r = s;
} else
{ q->next = r, q = r, r = r->next;
}
}
q->next = NIL;
data = r;
} else
{ data = NIL;
}
runs++;
/* merge this run with 0 or more runs off the top of the stack */
for (k = runs; 1 &~ k; k >>= 1)
{ q = *--sp;
r = &header;
while (q && p)
{ /* q precedes p */
compare(c, q, p);
if (c <= 0)
{ r->next = q, r = q, q = q->next;
if (c == remove_dups)
{ s = p->next;
FREE(p);
p = s;
}
} else
{ r->next = p, r = p, p = p->next;
}
}
r->next = q ? q : p;
p = header.next;
}
/* push the merged run onto the stack */
*sp++ = p;
}
if (sp == stack)
return NIL;
/* merge all the runs on the stack */
p = *--sp;
while (sp != stack)
{ q = *--sp;
r = &header;
while (q && p)
{ /* q precedes p */
compare(c, q, p);
if (c <= 0)
{ r->next = q, r = q, q = q->next;
if (c == remove_dups)
{ s = p->next;
FREE(p);
p = s;
}
} else
{ r->next = p, r = p, p = p->next;
}
}
r->next = q ? q : p;
p = header.next;
}
return p;
}
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Create a list on the global stack, just at the place the final result
will be.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
static int
prolog_list_to_sort_list(term_t t, int remove_dups, int key,
list *lp, Word *end)
{ GET_LD
Word l, tail;
list p;
intptr_t len;
int rc;
l = valTermRef(t);
len = skip_list(l, &tail PASS_LD);
if ( !(isNil(*tail) || /* proper list */
(isList(*tail) && remove_dups)) ) /* sort/2 on cyclic list */
{
if ( isVar(*tail) )
return PL_error(NULL, 0, NULL, ERR_INSTANTIATION);
else
return PL_error(NULL, 0, NULL, ERR_TYPE, ATOM_list, t);
}
if ( !hasGlobalSpace(len*3) )
{ if ( (rc=ensureGlobalSpace(len*3, ALLOW_GC)) != TRUE )
return raiseStackOverflow(rc);
l = valTermRef(t); /* may be shifted */
deRef(l);
}
p = (list)gTop;
*lp = p;
while(len-- > 0)
{ p->item.term = HeadList(l);
deRef(p->item.term);
if ( key )
{ word w = *p->item.term;
if ( hasFunctor(w, FUNCTOR_minus2) )
{ p->item.key = argTermP(w, 0);
deRef(p->item.key);
} else
{ PL_error("keysort", 2, NULL, ERR_TYPE,
ATOM_pair, pushWordAsTermRef(p->item.term));
popTermRef();
return FALSE;
}
}
l = TailList(l);
deRef(l);
if ( len > 0 )
{ assert(isList(*l));
p->next = p+1;
p++;
}
}
p->next = NULL;
*end = (Word)(p+1);
succeed;
}
static void
put_sort_list(term_t l, list sl)
{ GET_LD
*valTermRef(l) = consPtr(sl, TAG_COMPOUND|STG_GLOBAL);
for(;;)
{ list n = sl->next;
Word p = (Word)sl;
n = sl->next;
/* see also linkVal() */
p[1] = (needsRef(*sl->item.term) ? makeRef(sl->item.term)
: *sl->item.term);
p[0] = FUNCTOR_dot2;
if ( n )
{ p[2] = consPtr(n, TAG_COMPOUND|STG_GLOBAL);
sl = n;
} else
{ p[2] = ATOM_nil;
return;
}
}
}
static int
pl_nat_sort(term_t in, term_t out, int remove_dups, int compare_keys ARG_LD)
{ if ( PL_get_nil(in) )
return PL_unify_atom(out, ATOM_nil);
else
{ list l = 0;
term_t tmp = PL_new_term_ref();
Word top = NULL;
if ( prolog_list_to_sort_list(in, remove_dups, compare_keys, &l, &top) )
{ l = nat_sort(l, remove_dups, compare_keys);
put_sort_list(tmp, l);
gTop = top;
return PL_unify(out, tmp);
}
fail;
}
}
static
PRED_IMPL("sort", 2, sort, PL_FA_ISO)
{ PRED_LD
return pl_nat_sort(A1, A2, TRUE, FALSE PASS_LD);
}
static
PRED_IMPL("msort", 2, msort, 0)
{ PRED_LD
return pl_nat_sort(A1, A2, FALSE, FALSE PASS_LD);
}
static
PRED_IMPL("keysort", 2, keysort, PL_FA_ISO)
{ PRED_LD
return pl_nat_sort(A1, A2, FALSE, TRUE PASS_LD);
}
/*******************************
* PUBLISH PREDICATES *
*******************************/
BeginPredDefs(list)
PRED_DEF("is_list", 1, is_list, 0)
PRED_DEF("$length", 2, dlength, 0)
PRED_DEF("memberchk", 2, memberchk, 0)
PRED_DEF("sort", 2, sort, PL_FA_ISO)
PRED_DEF("msort", 2, msort, 0)
PRED_DEF("keysort", 2, keysort, PL_FA_ISO)
EndPredDefs
|