*
*/
-#ifdef TESTHARNESS
-#include <sys/types.h>
-typedef void SV;
-#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) (pTHX_ SV*, SV*);
-#endif /* TESTHARNESS */
typedef char * aptr; /* pointer for arithmetic on sizes */
typedef SV * gptr; /* pointers in our lists */
*/
-static void
+static IV
dynprep(pTHX_ gptr *list1, gptr *list2, size_t nmemb, SVCOMPARE_t cmp)
{
- int sense;
+ I32 sense;
register gptr *b, *p, *q, *t, *p2;
register gptr c, *last, *r;
gptr *savep;
+ IV runs = 0;
b = list1;
last = PINDEX(b, nmemb);
((t + 1) == last) &&
((cmp(aTHX_ *(p-1), *p) > 0) == sense))
savep = r = p = q = last;
- p2 = NEXT(p2) = p2 + (p - b);
+ p2 = NEXT(p2) = p2 + (p - b); ++runs;
if (sense) while (b < --p) {
c = *b;
*b++ = *p;
p = savep;
}
while (q < p) { /* simple pairs */
- p2 = NEXT(p2) = p2 + 2;
+ p2 = NEXT(p2) = p2 + 2; ++runs;
if (sense) {
c = *q++;
*(q-1) = *q;
} else q += 2;
}
if (((b = p) == t) && ((t+1) == last)) {
- NEXT(p2) = p2 + 1;
+ NEXT(p2) = p2 + 1; ++runs;
b++;
}
q = r;
} while (b < t);
sense = !sense;
}
- return;
+ return runs;
}
return;
}
+
+/* What perl needs (least) is another sort implementation in the core.
+ * So what's the story? The short (by jpl's standards) story is that
+ * the merge sort above, in use since 5.7, is as fast as, or faster than,
+ * qsort on many platforms, but slower than qsort, conspicuously so,
+ * on others. The most likely explanation is platform-specific
+ * differences in cache sizes and relative speeds.
+ *
+ * The quicksort divide-and-conquer algorithm guarantees that, as the
+ * problem is subdivided into smaller and smaller parts, the parts
+ * fit into smaller (and faster) caches. So it doesn't matter how
+ * many levels of cache exist, quicksort will "find" them, and,
+ * as long as smaller is faster, take advanatge of them.
+ *
+ * By contrast, consider how the quicksort algorithm above works.
+ * Suppose we have five runs (each typically of length 2 after dynprep).
+ *
+ * pass base aux
+ * 0 1 2 3 4 5
+ * 1 12 34 5
+ * 2 1234 5
+ * 3 12345
+ * 4 12345
+ *
+ * Adjacent pairs are merged in "grand sweeps" through the input.
+ * This means, on pass 1, the records in runs 1 and 2 aren't revisited until
+ * runs 3 and 4 are merged and the runs from run 5 have been copied.
+ * The only cache that matters is one large enough to hold *all* the input.
+ * On some platforms, this may be many times slower than smaller caches.
+ *
+ * The following pseudo-code uses the same basic merge algorithm,
+ * but in a divide-and-conquer way.
+ *
+ * # merge $runs runs at offset $offset of list $list1 into $list2.
+ * # all unmerged runs ($runs == 1) originate in list $base.
+ * sub mgsort2 {
+ * my ($offset, $runs, $base, $list1, $list2) = @_;
+ *
+ * if ($runs == 1) {
+ * if ($list1 is $base) copy run to $list2
+ * return offset of end of list (or copy)
+ * } else {
+ * $off2 = mgsort2($offset, $runs-($runs/2), $base, $list2, $list1)
+ * mgsort2($off2, $runs/2, $base, $list2, $list1)
+ * merge the adjacent runs at $offset of $list1 into $list2
+ * return the offset of the end of the merged runs
+ * }
+ * }
+ * mgsort2(0, $runs, $base, $aux, $base);
+ *
+ * For our 5 runs, the tree of calls looks like
+ *
+ * 5
+ * 3 2
+ * 2 1 1 1
+ * 1 1
+ *
+ * 1 2 3 4 5
+ *
+ * and the corresponding activity looks like
+ *
+ * copy runs 1 and 2 from base to aux
+ * merge runs 1 and 2 from aux to base
+ * (run 3 is where it belongs, no copy needed)
+ * merge runs 12 and 3 from base to aux
+ * (runs 4 and 5 are where they belong, no copy needed)
+ * merge runs 4 and 5 from base to aux
+ * merge runs 123 and 45 from aux to base
+ *
+ * Note that we merge runs 1 and 2 immediately after copying them,
+ * while they are still likely to be in fast cache. Similarly,
+ * run 3 is merged with run 12 while it still may be lingering in cache.
+ * This implementation should therefore enjoy much of the cache-friendly
+ * behavior that quicksort does. In addition, it does less copying
+ * than the original mergesort implementation (only runs 1 and 2 are copied)
+ * and the "balancing" of merges is better (merged runs comprise more nearly
+ * equal numbers of original runs).
+ *
+ * The actual cache-friendly implementation will use a pseudo-stack
+ * to avoid recursion, and will unroll processing of runs of length 2,
+ * but it is otherwise similar to the recursive implementation.
+ * If it's as good as the original mergesort implementation on all
+ * platforms, it should replace that implementation. For benchmarking,
+ * though, it is convenient to have both implementations available.
+ */
+
+typedef struct {
+ IV offset; /* offset of 1st of 2 runs at this level */
+ IV runs; /* how many runs must be combined into 1 */
+} off_runs; /* pseudo-stack element */
+
+STATIC void
+S_cfmergesortsv(pTHX_ gptr *base, size_t nmemb, SVCOMPARE_t cmp)
+{
+ IV i, run, runs, offset;
+ I32 sense, level;
+ int iwhich;
+ register gptr *f1, *f2, *t, *b, *p, *tp2, *l1, *l2, *q;
+ gptr *aux, *list1, *list2;
+ gptr *p1;
+ gptr small[SMALLSORT];
+ gptr *which[3];
+ off_runs stack[60], *stackp;
+
+ if (nmemb <= 1) return; /* sorted trivially */
+ if (nmemb <= SMALLSORT) aux = small; /* use stack for aux array */
+ else { New(799,aux,nmemb,gptr); } /* allocate auxilliary array */
+ level = 0;
+ stackp = stack;
+ stackp->runs = dynprep(aTHX_ base, aux, nmemb, cmp);
+ stackp->offset = offset = 0;
+ which[0] = which[2] = base;
+ which[1] = aux;
+ for (;;) {
+ /* On levels where both runs have be constructed (stackp->runs == 0),
+ * merge them, and note the offset of their end, in case the offset
+ * is needed at the next level up. Hop up a level, and,
+ * as long as stackp->runs is 0, keep merging.
+ */
+ if ((runs = stackp->runs) == 0) {
+ iwhich = level & 1;
+ list1 = which[iwhich]; /* area where runs are now */
+ list2 = which[++iwhich]; /* area for merged runs */
+ do {
+ offset = stackp->offset;
+ f1 = p1 = list1 + offset; /* start of first run */
+ p = tp2 = list2 + offset; /* where merged run will go */
+ t = NEXT(p); /* where first run ends */
+ f2 = l1 = POTHER(t, list2, list1); /* ... on the other side */
+ t = NEXT(t); /* where second runs ends */
+ l2 = POTHER(t, list2, list1); /* ... on the other side */
+ offset = PNELEM(list2, 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;
+ }
+
+
+ /* 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;
+ }
+
+
+ /* 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.
+ */
+
+ b++;
+ while (b < t) {
+ p = PINDEX(b, (PNELEM(b, t) - 1) / 2);
+ if (cmp(aTHX_ *q, *p) <= sense) {
+ t = p;
+ } else b = p + 1;
+ }
+
+
+ /* Copy all the strictly low elements */
+
+ if (q == f1) {
+ FROMTOUPTO(f2, tp2, t);
+ *tp2++ = *f1++;
+ } else {
+ FROMTOUPTO(f1, tp2, t);
+ *tp2++ = *f2++;
+ }
+ }
+
+
+ /* 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);
+
+ if (--level == 0) goto done;
+ --stackp;
+ t = list1; list1 = list2; list2 = t; /* swap lists */
+ } while ((runs = stackp->runs) == 0);
+ }
+
+
+ stackp->runs = 0; /* current run will finish level */
+ /* While there are more than 2 runs remaining,
+ * turn them into exactly 2 runs (at the "other" level),
+ * each made up of approximately half the runs.
+ * Stack the second half for later processing,
+ * and set about producing the first half now.
+ */
+ while (runs > 2) {
+ ++level;
+ ++stackp;
+ stackp->offset = offset;
+ runs -= stackp->runs = runs / 2;
+ }
+ /* We must construct a single run from 1 or 2 runs.
+ * All the original runs are in which[0] == base.
+ * The run we construct must end up in which[level&1].
+ */
+ iwhich = level & 1;
+ if (runs == 1) {
+ /* Constructing a single run from a single run.
+ * If it's where it belongs already, there's nothing to do.
+ * Otherwise, copy it to where it belongs.
+ * A run of 1 is either a singleton at level 0,
+ * or the second half of a split 3. In neither event
+ * is it necessary to set offset. It will be set by the merge
+ * that immediately follows.
+ */
+ if (iwhich) { /* Belongs in aux, currently in base */
+ f1 = b = PINDEX(base, offset); /* where list starts */
+ f2 = PINDEX(aux, offset); /* where list goes */
+ t = NEXT(f2); /* where list will end */
+ offset = PNELEM(aux, t); /* offset thereof */
+ t = PINDEX(base, offset); /* where it currently ends */
+ FROMTOUPTO(f1, f2, t); /* copy */
+ NEXT(b) = t; /* set up parallel pointer */
+ } else if (level == 0) goto done; /* single run at level 0 */
+ } else {
+ /* Constructing a single run from two runs.
+ * The merge code at the top will do that.
+ * We need only make sure the two runs are in the "other" array,
+ * so they'll end up in the correct array after the merge.
+ */
+ ++level;
+ ++stackp;
+ stackp->offset = offset;
+ stackp->runs = 0; /* take care of both runs, trigger merge */
+ if (!iwhich) { /* Merged runs belong in aux, copy 1st */
+ f1 = b = PINDEX(base, offset); /* where first run starts */
+ f2 = PINDEX(aux, offset); /* where it will be copied */
+ t = NEXT(f2); /* where first run will end */
+ offset = PNELEM(aux, t); /* offset thereof */
+ p = PINDEX(base, offset); /* end of first run */
+ t = NEXT(t); /* where second run will end */
+ t = PINDEX(base, PNELEM(aux, t)); /* where it now ends */
+ FROMTOUPTO(f1, f2, t); /* copy both runs */
+ NEXT(b) = p; /* paralled pointer for 1st */
+ NEXT(p) = t; /* ... and for second */
+ }
+ }
+ }
+done:
+ if (aux != small) Safefree(aux); /* free iff allocated */
+ return;
+}
+
/*
* The quicksort implementation was derived from source code contributed
* by Tom Horsley.
sortsvp = S_qsortsv;
else {
if (hints & HINT_SORT_MERGESORT)
- sortsvp = S_mergesortsv;
+ sortsvp = S_cfmergesortsv;
else
sortsvp = S_mergesortsv;
}
}
return sv_cmp_locale(str1, str2);
}
-
-
projects / p5sagit/p5-mst-13.2.git / commitdiff