diff options
Diffstat (limited to 'pp_ctl.c')
| -rw-r--r-- | pp_ctl.c | 771 |
1 files changed, 723 insertions, 48 deletions
@@ -37,9 +37,8 @@ static I32 dopoptolabel _((char *label)); static I32 dopoptoloop _((I32 startingblock)); static I32 dopoptosub _((I32 startingblock)); static void save_lines _((AV *array, SV *sv)); -static int sortcv _((const void *, const void *)); -static int sortcmp _((const void *, const void *)); -static int sortcmp_locale _((const void *, const void *)); +static I32 sortcv _((SV *a, SV *b)); +static void qsortsv _((SV **array, size_t num_elts, I32 (*fun)(SV *a, SV *b))); static OP *doeval _((int gimme, OP** startop)); #endif @@ -764,10 +763,10 @@ PP(pp_sort) #ifdef PERL_OBJECT MUTEX_LOCK(&sort_mutex); pSortPerl = this; - qsort((char*)(myorigmark+1), max, sizeof(SV*), SortCv); + qsortsv((myorigmark+1), max, SortCv); MUTEX_UNLOCK(&sort_mutex); #else - qsort((char*)(myorigmark+1), max, sizeof(SV*), sortcv); + qsortsv((myorigmark+1), max, sortcv); #endif POPBLOCK(cx,curpm); @@ -782,12 +781,12 @@ PP(pp_sort) #ifdef PERL_OBJECT MUTEX_LOCK(&sort_mutex); pSortPerl = this; - qsort((char*)(ORIGMARK+1), max, sizeof(SV*), - (op->op_private & OPpLOCALE) ? SortCmpLocale : SortCmp); + qsortsv(ORIGMARK+1, max, + (op->op_private & OPpLOCALE) ? sv_cmp_locale : sv_cmp); MUTEX_UNLOCK(&sort_mutex); #else - qsort((char*)(ORIGMARK+1), max, sizeof(SV*), - (op->op_private & OPpLOCALE) ? sortcmp_locale : sortcmp); + qsortsv(ORIGMARK+1, max, + (op->op_private & OPpLOCALE) ? sv_cmp_locale : sv_cmp); #endif } } @@ -1251,25 +1250,23 @@ PP(pp_caller) AvREAL_off(dbargs); /* XXX Should be REIFY */ } - if (AvMAX(dbargs) < AvFILL(ary) + off) - av_extend(dbargs, AvFILL(ary) + off); - Copy(AvALLOC(ary), AvARRAY(dbargs), AvFILL(ary) + 1 + off, SV*); - AvFILL(dbargs) = AvFILL(ary) + off; + if (AvMAX(dbargs) < AvFILLp(ary) + off) + av_extend(dbargs, AvFILLp(ary) + off); + Copy(AvALLOC(ary), AvARRAY(dbargs), AvFILLp(ary) + 1 + off, SV*); + AvFILLp(dbargs) = AvFILLp(ary) + off; } RETURN; } -STATIC int -sortcv(const void *a, const void *b) +STATIC I32 +sortcv(SV *a, SV *b) { dTHR; - SV * const *str1 = (SV * const *)a; - SV * const *str2 = (SV * const *)b; I32 oldsaveix = savestack_ix; I32 oldscopeix = scopestack_ix; I32 result; - GvSV(firstgv) = *str1; - GvSV(secondgv) = *str2; + GvSV(firstgv) = a; + GvSV(secondgv) = b; stack_sp = stack_base; op = sortcop; CALLRUNOPS(); @@ -1285,18 +1282,6 @@ sortcv(const void *a, const void *b) return result; } -STATIC int -sortcmp(const void *a, const void *b) -{ - return sv_cmp(*(SV * const *)a, *(SV * const *)b); -} - -STATIC int -sortcmp_locale(const void *a, const void *b) -{ - return sv_cmp_locale(*(SV * const *)a, *(SV * const *)b); -} - PP(pp_reset) { djSP; @@ -1399,7 +1384,7 @@ PP(pp_enteriter) cx->blk_loop.iterary = (AV*)SvREFCNT_inc(POPs); else { cx->blk_loop.iterary = curstack; - AvFILL(curstack) = sp - stack_base; + AvFILLp(curstack) = sp - stack_base; cx->blk_loop.iterix = MARK - stack_base; } @@ -1673,7 +1658,7 @@ PP(pp_redo) static OP* lastgotoprobe; -STATIC OP * +static OP * dofindlabel(OP *o, char *label, OP **opstack, OP **oplimit) { OP *kid; @@ -1765,7 +1750,7 @@ PP(pp_goto) if (cx->blk_sub.hasargs) { /* put @_ back onto stack */ AV* av = cx->blk_sub.argarray; - items = AvFILL(av) + 1; + items = AvFILLp(av) + 1; stack_sp++; EXTEND(stack_sp, items); /* @_ could have been extended. */ Copy(AvARRAY(av), stack_sp, items, SV*); @@ -1799,7 +1784,7 @@ PP(pp_goto) } else { stack_sp--; /* There is no cv arg. */ - (void)(*CvXSUB(cv))(THIS_ cv); + (void)(*CvXSUB(cv))(cv); } LEAVE; return pop_return(); @@ -1815,10 +1800,10 @@ PP(pp_goto) else { /* save temporaries on recursion? */ if (CvDEPTH(cv) == 100 && dowarn) sub_crush_depth(cv); - if (CvDEPTH(cv) > AvFILL(padlist)) { + if (CvDEPTH(cv) > AvFILLp(padlist)) { AV *newpad = newAV(); SV **oldpad = AvARRAY(svp[CvDEPTH(cv)-1]); - I32 ix = AvFILL((AV*)svp[1]); + I32 ix = AvFILLp((AV*)svp[1]); svp = AvARRAY(svp[0]); for ( ;ix > 0; ix--) { if (svp[ix] != &sv_undef) { @@ -1852,7 +1837,7 @@ PP(pp_goto) AvFLAGS(av) = AVf_REIFY; } av_store(padlist, CvDEPTH(cv), (SV*)newpad); - AvFILL(padlist) = CvDEPTH(cv); + AvFILLp(padlist) = CvDEPTH(cv); svp = AvARRAY(padlist); } } @@ -1860,7 +1845,7 @@ PP(pp_goto) if (!cx->blk_sub.hasargs) { AV* av = (AV*)curpad[0]; - items = AvFILL(av) + 1; + items = AvFILLp(av) + 1; if (items) { /* Mark is at the end of the stack. */ EXTEND(sp, items); @@ -1900,7 +1885,7 @@ PP(pp_goto) } } Copy(mark,AvARRAY(av),items,SV*); - AvFILL(av) = items - 1; + AvFILLp(av) = items - 1; while (items--) { if (*mark) @@ -2001,7 +1986,7 @@ PP(pp_goto) if (op->op_type == OP_ENTERITER) DIE("Can't \"goto\" into the middle of a foreach loop", label); - (CALLOP->op_ppaddr)(ARGS); + (*op->op_ppaddr)(ARGS); } op = oldop; } @@ -2089,7 +2074,7 @@ PP(pp_cswitch) /* Eval. */ -STATIC void +static void save_lines(AV *array, SV *sv) { register char *s = SvPVX(sv); @@ -2113,7 +2098,7 @@ save_lines(AV *array, SV *sv) } } -STATIC OP * +static OP * docatch(OP *o) { dTHR; @@ -2142,7 +2127,7 @@ docatch(OP *o) restartop = 0; /* FALL THROUGH */ case 0: - CALLRUNOPS(); + runops(); break; } JMPENV_POP; @@ -2205,7 +2190,7 @@ sv_compile_2op(SV *sv, OP** startop, char *code, AV** avp) } /* With USE_THREADS, eval_owner must be held on entry to doeval */ -STATIC OP * +static OP * doeval(int gimme, OP** startop) { dSP; @@ -2213,6 +2198,7 @@ doeval(int gimme, OP** startop) HV *newstash; CV *caller; AV* comppadlist; + I32 i; in_eval = 1; @@ -2229,6 +2215,16 @@ doeval(int gimme, OP** startop) SAVEI32(max_intro_pending); caller = compcv; + for (i = cxstack_ix - 1; i >= 0; i--) { + PERL_CONTEXT *cx = &cxstack[i]; + if (cx->cx_type == CXt_EVAL) + break; + else if (cx->cx_type == CXt_SUB) { + caller = cx->blk_sub.cv; + break; + } + } + SAVESPTR(compcv); compcv = (CV*)NEWSV(1104,0); sv_upgrade((SV *)compcv, SVt_PVCV); @@ -2629,10 +2625,10 @@ PP(pp_leaveeval) * (Note that the fact that compcv and friends are still set here * is, AFAIK, an accident.) --Chip */ - if (AvFILL(comppad_name) >= 0) { + if (AvFILLp(comppad_name) >= 0) { SV **svp = AvARRAY(comppad_name); I32 ix; - for (ix = AvFILL(comppad_name); ix >= 0; ix--) { + for (ix = AvFILLp(comppad_name); ix >= 0; ix--) { SV *sv = svp[ix]; if (sv && sv != &sv_undef && *SvPVX(sv) == '&') { SvREFCNT_dec(sv); @@ -2743,7 +2739,7 @@ PP(pp_leavetry) RETURN; } -STATIC void +static void doparseform(SV *sv) { STRLEN len; @@ -2921,4 +2917,683 @@ doparseform(SV *sv) SvCOMPILED_on(sv); } +/* + * The rest of this file was derived from source code contributed + * by Tom Horsley. + * + * NOTE: this code was derived from Tom Horsley's qsort replacement + * and should not be confused with the original code. + */ + +/* Copyright (C) Tom Horsley, 1997. All rights reserved. + + Permission granted to distribute under the same terms as perl which are + (briefly): + + This program is free software; you can redistribute it and/or modify + it under the terms of either: + + a) the GNU General Public License as published by the Free + Software Foundation; either version 1, or (at your option) any + later version, or + + b) the "Artistic License" which comes with this Kit. + + Details on the perl license can be found in the perl source code which + may be located via the www.perl.com web page. + + This is the most wonderfulest possible qsort I can come up with (and + still be mostly portable) My (limited) tests indicate it consistently + does about 20% fewer calls to compare than does the qsort in the Visual + C++ library, other vendors may vary. + + Some of the ideas in here can be found in "Algorithms" by Sedgewick, + others I invented myself (or more likely re-invented since they seemed + pretty obvious once I watched the algorithm operate for a while). + + Most of this code was written while watching the Marlins sweep the Giants + in the 1997 National League Playoffs - no Braves fans allowed to use this + code (just kidding :-). + + I realize that if I wanted to be true to the perl tradition, the only + comment in this file would be something like: + + ...they shuffled back towards the rear of the line. 'No, not at the + rear!' the slave-driver shouted. 'Three files up. And stay there... + + However, I really needed to violate that tradition just so I could keep + track of what happens myself, not to mention some poor fool trying to + understand this years from now :-). +*/ + +/* ********************************************************** Configuration */ + +#ifndef QSORT_ORDER_GUESS +#define QSORT_ORDER_GUESS 2 /* Select doubling version of the netBSD trick */ +#endif + +/* QSORT_MAX_STACK is the largest number of partitions that can be stacked up for + future processing - a good max upper bound is log base 2 of memory size + (32 on 32 bit machines, 64 on 64 bit machines, etc). In reality can + safely be smaller than that since the program is taking up some space and + most operating systems only let you grab some subset of contiguous + memory (not to mention that you are normally sorting data larger than + 1 byte element size :-). +*/ +#ifndef QSORT_MAX_STACK +#define QSORT_MAX_STACK 32 +#endif + +/* QSORT_BREAK_EVEN is the size of the largest partition we should insertion sort. + Anything bigger and we use qsort. If you make this too small, the qsort + will probably break (or become less efficient), because it doesn't expect + the middle element of a partition to be the same as the right or left - + you have been warned). +*/ +#ifndef QSORT_BREAK_EVEN +#define QSORT_BREAK_EVEN 6 +#endif + +/* ************************************************************* Data Types */ + +/* hold left and right index values of a partition waiting to be sorted (the + partition includes both left and right - right is NOT one past the end or + anything like that). +*/ +struct partition_stack_entry { + int left; + int right; +#ifdef QSORT_ORDER_GUESS + int qsort_break_even; +#endif +}; + +/* ******************************************************* Shorthand Macros */ + +/* Note that these macros will be used from inside the qsort function where + we happen to know that the variable 'elt_size' contains the size of an + array element and the variable 'temp' points to enough space to hold a + temp element and the variable 'array' points to the array being sorted + and 'compare' is the pointer to the compare routine. + + Also note that there are very many highly architecture specific ways + these might be sped up, but this is simply the most generally portable + code I could think of. +*/ +/* Return < 0 == 0 or > 0 as the value of elt1 is < elt2, == elt2, > elt2 +*/ +#define qsort_cmp(elt1, elt2) \ + ((*compare)(array[elt1], array[elt2])) + +#ifdef QSORT_ORDER_GUESS +#define QSORT_NOTICE_SWAP swapped++; +#else +#define QSORT_NOTICE_SWAP +#endif + +/* swaps contents of array elements elt1, elt2. +*/ +#define qsort_swap(elt1, elt2) \ + STMT_START { \ + QSORT_NOTICE_SWAP \ + temp = array[elt1]; \ + array[elt1] = array[elt2]; \ + array[elt2] = temp; \ + } STMT_END + +/* rotate contents of elt1, elt2, elt3 such that elt1 gets elt2, elt2 gets + elt3 and elt3 gets elt1. +*/ +#define qsort_rotate(elt1, elt2, elt3) \ + STMT_START { \ + QSORT_NOTICE_SWAP \ + temp = array[elt1]; \ + array[elt1] = array[elt2]; \ + array[elt2] = array[elt3]; \ + array[elt3] = temp; \ + } STMT_END + +/* ************************************************************ Debug stuff */ + +#ifdef QSORT_DEBUG + +static void +break_here() +{ + return; /* good place to set a breakpoint */ +} + +#define qsort_assert(t) (void)( (t) || (break_here(), 0) ) + +static void +doqsort_all_asserts( + void * array, + size_t num_elts, + size_t elt_size, + int (*compare)(const void * elt1, const void * elt2), + int pc_left, int pc_right, int u_left, int u_right) +{ + int i; + + qsort_assert(pc_left <= pc_right); + qsort_assert(u_right < pc_left); + qsort_assert(pc_right < u_left); + for (i = u_right + 1; i < pc_left; ++i) { + qsort_assert(qsort_cmp(i, pc_left) < 0); + } + for (i = pc_left; i < pc_right; ++i) { + qsort_assert(qsort_cmp(i, pc_right) == 0); + } + for (i = pc_right + 1; i < u_left; ++i) { + qsort_assert(qsort_cmp(pc_right, i) < 0); + } +} + +#define qsort_all_asserts(PC_LEFT, PC_RIGHT, U_LEFT, U_RIGHT) \ + doqsort_all_asserts(array, num_elts, elt_size, compare, \ + PC_LEFT, PC_RIGHT, U_LEFT, U_RIGHT) + +#else + +#define qsort_assert(t) ((void)0) + +#define qsort_all_asserts(PC_LEFT, PC_RIGHT, U_LEFT, U_RIGHT) ((void)0) + +#endif + +/* ****************************************************************** qsort */ + +void +qsortsv( + SV ** array, + size_t num_elts, + I32 (*compare)(SV *a, SV *b)) +{ + register SV * temp; + + struct partition_stack_entry partition_stack[QSORT_MAX_STACK]; + int next_stack_entry = 0; + + int part_left; + int part_right; +#ifdef QSORT_ORDER_GUESS + int qsort_break_even; + int swapped; +#endif + + /* Make sure we actually have work to do. + */ + if (num_elts <= 1) { + return; + } + + /* Setup the initial partition definition and fall into the sorting loop + */ + part_left = 0; + part_right = (int)(num_elts - 1); +#ifdef QSORT_ORDER_GUESS + qsort_break_even = QSORT_BREAK_EVEN; +#else +#define qsort_break_even QSORT_BREAK_EVEN +#endif + for ( ; ; ) { + if ((part_right - part_left) >= qsort_break_even) { + /* OK, this is gonna get hairy, so lets try to document all the + concepts and abbreviations and variables and what they keep + track of: + + pc: pivot chunk - the set of array elements we accumulate in the + middle of the partition, all equal in value to the original + pivot element selected. The pc is defined by: + + pc_left - the leftmost array index of the pc + pc_right - the rightmost array index of the pc + + we start with pc_left == pc_right and only one element + in the pivot chunk (but it can grow during the scan). + + u: uncompared elements - the set of elements in the partition + we have not yet compared to the pivot value. There are two + uncompared sets during the scan - one to the left of the pc + and one to the right. + + u_right - the rightmost index of the left side's uncompared set + u_left - the leftmost index of the right side's uncompared set + + The leftmost index of the left sides's uncompared set + doesn't need its own variable because it is always defined + by the leftmost edge of the whole partition (part_left). The + same goes for the rightmost edge of the right partition + (part_right). + + We know there are no uncompared elements on the left once we + get u_right < part_left and no uncompared elements on the + right once u_left > part_right. When both these conditions + are met, we have completed the scan of the partition. + + Any elements which are between the pivot chunk and the + uncompared elements should be less than the pivot value on + the left side and greater than the pivot value on the right + side (in fact, the goal of the whole algorithm is to arrange + for that to be true and make the groups of less-than and + greater-then elements into new partitions to sort again). + + As you marvel at the complexity of the code and wonder why it + has to be so confusing. Consider some of the things this level + of confusion brings: + + Once I do a compare, I squeeze every ounce of juice out of it. I + never do compare calls I don't have to do, and I certainly never + do redundant calls. + + I also never swap any elements unless I can prove there is a + good reason. Many sort algorithms will swap a known value with + an uncompared value just to get things in the right place (or + avoid complexity :-), but that uncompared value, once it gets + compared, may then have to be swapped again. A lot of the + complexity of this code is due to the fact that it never swaps + anything except compared values, and it only swaps them when the + compare shows they are out of position. + */ + int pc_left, pc_right; + int u_right, u_left; + + int s; + + pc_left = ((part_left + part_right) / 2); + pc_right = pc_left; + u_right = pc_left - 1; + u_left = pc_right + 1; + + /* Qsort works best when the pivot value is also the median value + in the partition (unfortunately you can't find the median value + without first sorting :-), so to give the algorithm a helping + hand, we pick 3 elements and sort them and use the median value + of that tiny set as the pivot value. + + Some versions of qsort like to use the left middle and right as + the 3 elements to sort so they can insure the ends of the + partition will contain values which will stop the scan in the + compare loop, but when you have to call an arbitrarily complex + routine to do a compare, its really better to just keep track of + array index values to know when you hit the edge of the + partition and avoid the extra compare. An even better reason to + avoid using a compare call is the fact that you can drop off the + edge of the array if someone foolishly provides you with an + unstable compare function that doesn't always provide consistent + results. + + So, since it is simpler for us to compare the three adjacent + elements in the middle of the partition, those are the ones we + pick here (conveniently pointed at by u_right, pc_left, and + u_left). The values of the left, center, and right elements + are refered to as l c and r in the following comments. + */ + +#ifdef QSORT_ORDER_GUESS + swapped = 0; +#endif + s = qsort_cmp(u_right, pc_left); + if (s < 0) { + /* l < c */ + s = qsort_cmp(pc_left, u_left); + /* if l < c, c < r - already in order - nothing to do */ + if (s == 0) { + /* l < c, c == r - already in order, pc grows */ + ++pc_right; + qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1); + } else if (s > 0) { + /* l < c, c > r - need to know more */ + s = qsort_cmp(u_right, u_left); + if (s < 0) { + /* l < c, c > r, l < r - swap c & r to get ordered */ + qsort_swap(pc_left, u_left); + qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1); + } else if (s == 0) { + /* l < c, c > r, l == r - swap c&r, grow pc */ + qsort_swap(pc_left, u_left); + --pc_left; + qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1); + } else { + /* l < c, c > r, l > r - make lcr into rlc to get ordered */ + qsort_rotate(pc_left, u_right, u_left); + qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1); + } + } + } else if (s == 0) { + /* l == c */ + s = qsort_cmp(pc_left, u_left); + if (s < 0) { + /* l == c, c < r - already in order, grow pc */ + --pc_left; + qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1); + } else if (s == 0) { + /* l == c, c == r - already in order, grow pc both ways */ + --pc_left; + ++pc_right; + qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1); + } else { + /* l == c, c > r - swap l & r, grow pc */ + qsort_swap(u_right, u_left); + ++pc_right; + qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1); + } + } else { + /* l > c */ + s = qsort_cmp(pc_left, u_left); + if (s < 0) { + /* l > c, c < r - need to know more */ + s = qsort_cmp(u_right, u_left); + if (s < 0) { + /* l > c, c < r, l < r - swap l & c to get ordered */ + qsort_swap(u_right, pc_left); + qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1); + } else if (s == 0) { + /* l > c, c < r, l == r - swap l & c, grow pc */ + qsort_swap(u_right, pc_left); + ++pc_right; + qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1); + } else { + /* l > c, c < r, l > r - rotate lcr into crl to order */ + qsort_rotate(u_right, pc_left, u_left); + qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1); + } + } else if (s == 0) { + /* l > c, c == r - swap ends, grow pc */ + qsort_swap(u_right, u_left); + --pc_left; + qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1); + } else { + /* l > c, c > r - swap ends to get in order */ + qsort_swap(u_right, u_left); + qsort_all_asserts(pc_left, pc_right, u_left + 1, u_right - 1); + } + } + /* We now know the 3 middle elements have been compared and + arranged in the desired order, so we can shrink the uncompared + sets on both sides + */ + --u_right; + ++u_left; + qsort_all_asserts(pc_left, pc_right, u_left, u_right); + + /* The above massive nested if was the simple part :-). We now have + the middle 3 elements ordered and we need to scan through the + uncompared sets on either side, swapping elements that are on + the wrong side or simply shuffling equal elements around to get + all equal elements into the pivot chunk. + */ + + for ( ; ; ) { + int still_work_on_left; + int still_work_on_right; + + /* Scan the uncompared values on the left. If I find a value + equal to the pivot value, move it over so it is adjacent to + the pivot chunk and expand the pivot chunk. If I find a value + less than the pivot value, then just leave it - its already + on the correct side of the partition. If I find a greater + value, then stop the scan. + */ + while (still_work_on_left = (u_right >= part_left)) { + s = qsort_cmp(u_right, pc_left); + if (s < 0) { + --u_right; + } else if (s == 0) { + --pc_left; + if (pc_left != u_right) { + qsort_swap(u_right, pc_left); + } + --u_right; + } else { + break; + } + qsort_assert(u_right < pc_left); + qsort_assert(pc_left <= pc_right); + qsort_assert(qsort_cmp(u_right + 1, pc_left) <= 0); + qsort_assert(qsort_cmp(pc_left, pc_right) == 0); + } + + /* Do a mirror image scan of uncompared values on the right + */ + while (still_work_on_right = (u_left <= part_right)) { + s = qsort_cmp(pc_right, u_left); + if (s < 0) { + ++u_left; + } else if (s == 0) { + ++pc_right; + if (pc_right != u_left) { + qsort_swap(pc_right, u_left); + } + ++u_left; + } else { + break; + } + qsort_assert(u_left > pc_right); + qsort_assert(pc_left <= pc_right); + qsort_assert(qsort_cmp(pc_right, u_left - 1) <= 0); + qsort_assert(qsort_cmp(pc_left, pc_right) == 0); + } + + if (still_work_on_left) { + /* I know I have a value on the left side which needs to be + on the right side, but I need to know more to decide + exactly the best thing to do with it. + */ + if (still_work_on_right) { + /* I know I have values on both side which are out of + position. This is a big win because I kill two birds + with one swap (so to speak). I can advance the + uncompared pointers on both sides after swapping both + of them into the right place. + */ + qsort_swap(u_right, u_left); + --u_right; + ++u_left; + qsort_all_asserts(pc_left, pc_right, u_left, u_right); + } else { + /* I have an out of position value on the left, but the + right is fully scanned, so I "slide" the pivot chunk + and any less-than values left one to make room for the + greater value over on the right. If the out of position + value is immediately adjacent to the pivot chunk (there + are no less-than values), I can do that with a swap, + otherwise, I have to rotate one of the less than values + into the former position of the out of position value + and the right end of the pivot chunk into the left end + (got all that?). + */ + --pc_left; + if (pc_left == u_right) { + qsort_swap(u_right, pc_right); + qsort_all_asserts(pc_left, pc_right-1, u_left, u_right-1); + } else { + qsort_rotate(u_right, pc_left, pc_right); + qsort_all_asserts(pc_left, pc_right-1, u_left, u_right-1); + } + --pc_right; + --u_right; + } + } else if (still_work_on_right) { + /* Mirror image of complex case above: I have an out of + position value on the right, but the left is fully + scanned, so I need to shuffle things around to make room + for the right value on the left. + */ + ++pc_right; + if (pc_right == u_left) { + qsort_swap(u_left, pc_left); + qsort_all_asserts(pc_left+1, pc_right, u_left+1, u_right); + } else { + qsort_rotate(pc_right, pc_left, u_left); + qsort_all_asserts(pc_left+1, pc_right, u_left+1, u_right); + } + ++pc_left; + ++u_left; + } else { + /* No more scanning required on either side of partition, + break out of loop and figure out next set of partitions + */ + break; + } + } + + /* The elements in the pivot chunk are now in the right place. They + will never move or be compared again. All I have to do is decide + what to do with the stuff to the left and right of the pivot + chunk. + + Notes on the QSORT_ORDER_GUESS ifdef code: + + 1. If I just built these partitions without swapping any (or + very many) elements, there is a chance that the elements are + already ordered properly (being properly ordered will + certainly result in no swapping, but the converse can't be + proved :-). + + 2. A (properly written) insertion sort will run faster on + already ordered data than qsort will. + + 3. Perhaps there is some way to make a good guess about + switching to an insertion sort earlier than partition size 6 + (for instance - we could save the partition size on the stack + and increase the size each time we find we didn't swap, thus + switching to insertion sort earlier for partitions with a + history of not swapping). + + 4. Naturally, if I just switch right away, it will make + artificial benchmarks with pure ascending (or descending) + data look really good, but is that a good reason in general? + Hard to say... + */ + +#ifdef QSORT_ORDER_GUESS + if (swapped < 3) { +#if QSORT_ORDER_GUESS == 1 + qsort_break_even = (part_right - part_left) + 1; +#endif +#if QSORT_ORDER_GUESS == 2 + qsort_break_even *= 2; +#endif +#if QSORT_ORDER_GUESS == 3 + int prev_break = qsort_break_even; + qsort_break_even *= qsort_break_even; + if (qsort_break_even < prev_break) { + qsort_break_even = (part_right - part_left) + 1; + } +#endif + } else { + qsort_break_even = QSORT_BREAK_EVEN; + } +#endif + + if (part_left < pc_left) { + /* There are elements on the left which need more processing. + Check the right as well before deciding what to do. + */ + if (pc_right < part_right) { + /* We have two partitions to be sorted. Stack the biggest one + and process the smallest one on the next iteration. This + minimizes the stack height by insuring that any additional + stack entries must come from the smallest partition which + (because it is smallest) will have the fewest + opportunities to generate additional stack entries. + */ + if ((part_right - pc_right) > (pc_left - part_left)) { + /* stack the right partition, process the left */ + partition_stack[next_stack_entry].left = pc_right + 1; + partition_stack[next_stack_entry].right = part_right; +#ifdef QSORT_ORDER_GUESS + partition_stack[next_stack_entry].qsort_break_even = qsort_break_even; +#endif + part_right = pc_left - 1; + } else { + /* stack the left partition, process the right */ + partition_stack[next_stack_entry].left = part_left; + partition_stack[next_stack_entry].right = pc_left - 1; +#ifdef QSORT_ORDER_GUESS + partition_stack[next_stack_entry].qsort_break_even = qsort_break_even; +#endif + part_left = pc_right + 1; + } + qsort_assert(next_stack_entry < QSORT_MAX_STACK); + ++next_stack_entry; + } else { + /* The elements on the left are the only remaining elements + that need sorting, arrange for them to be processed as the + next partition. + */ + part_right = pc_left - 1; + } + } else if (pc_right < part_right) { + /* There is only one chunk on the right to be sorted, make it + the new partition and loop back around. + */ + part_left = pc_right + 1; + } else { + /* This whole partition wound up in the pivot chunk, so + we need to get a new partition off the stack. + */ + if (next_stack_entry == 0) { + /* the stack is empty - we are done */ + break; + } + --next_stack_entry; + part_left = partition_stack[next_stack_entry].left; + part_right = partition_stack[next_stack_entry].right; +#ifdef QSORT_ORDER_GUESS + qsort_break_even = partition_stack[next_stack_entry].qsort_break_even; +#endif + } + } else { + /* This partition is too small to fool with qsort complexity, just + do an ordinary insertion sort to minimize overhead. + */ + int i; + /* Assume 1st element is in right place already, and start checking + at 2nd element to see where it should be inserted. + */ + for (i = part_left + 1; i <= part_right; ++i) { + int j; + /* Scan (backwards - just in case 'i' is already in right place) + through the elements already sorted to see if the ith element + belongs ahead of one of them. + */ + for (j = i - 1; j >= part_left; --j) { + if (qsort_cmp(i, j) >= 0) { + /* i belongs right after j + */ + break; + } + } + ++j; + if (j != i) { + /* Looks like we really need to move some things + */ + temp = array[i]; + for (--i; i >= j; --i) + array[i + 1] = array[i]; + array[j] = temp; + } + } + + /* That partition is now sorted, grab the next one, or get out + of the loop if there aren't any more. + */ + + if (next_stack_entry == 0) { + /* the stack is empty - we are done */ + break; + } + --next_stack_entry; + part_left = partition_stack[next_stack_entry].left; + part_right = partition_stack[next_stack_entry].right; +#ifdef QSORT_ORDER_GUESS + qsort_break_even = partition_stack[next_stack_entry].qsort_break_even; +#endif + } + } + + /* Believe it or not, the array is sorted at this point! */ +} |