/* * * This file is part of * MakeIndex - A formatter and format independent index processor * * This file is public domain software donated by * Nelson Beebe (beebe@science.utah.edu). * */ /* * qsort.c: Our own version of the system qsort routine which is faster by an * average of 25%, with lows and highs of 10% and 50%. The THRESHold below is * the insertion sort threshold, and has been adjusted for records of size 48 * bytes. The MTHREShold is where we stop finding a better median. */ /* #include -- mkind.h includes this */ #include "mkind.h" /* only for type declarations */ #define THRESH 4 /* threshold for insertion */ #define MTHRESH 6 /* threshold for median */ static int qsz; /* size of each record */ static int thresh; /* THRESHold in chars */ static int mthresh; /* MTHRESHold in chars */ static int (*qcmp) ARGS((char*,char*)); /* the comparison routine */ static void qst ARGS((char *base, char *max)); /* * qqsort: First, set up some global parameters for qst to share. Then, * quicksort with qst(), and then a cleanup insertion sort ourselves. Sound * simple? It's not... */ void #if STDC qqsort(char *base, int n, int size, int (*compar) ARGS((char*,char*))) #else qqsort(base, n, size, compar) char *base; int n; int size; int (*compar) ARGS((char*,char*)); #endif { register char *i; register char *j; register char *lo; register char *hi; register char *min; register char c; char *max; if (n <= 1) return; qsz = size; qcmp = compar; thresh = qsz * THRESH; mthresh = qsz * MTHRESH; max = base + n * qsz; if (n >= THRESH) { qst(base, max); hi = base + thresh; } else { hi = max; } /* * First put smallest element, which must be in the first THRESH, in the * first position as a sentinel. This is done just by searching the * first THRESH elements (or the first n if n < THRESH), finding the min, * and swapping it into the first position. */ for (j = lo = base; (lo += qsz) < hi;) { if ((*qcmp) (j, lo) > 0) j = lo; } if (j != base) { /* swap j into place */ for (i = base, hi = base + qsz; i < hi;) { c = *j; *j++ = *i; *i++ = c; } } /* * With our sentinel in place, we now run the following hyper-fast * insertion sort. For each remaining element, min, from [1] to [n-1], * set hi to the index of the element AFTER which this one goes. Then, do * the standard insertion sort shift on a character at a time basis for * each element in the frob. */ for (min = base; (hi = min += qsz) < max;) { while ((*qcmp) (hi -= qsz, min) > 0); if ((hi += qsz) != min) { for (lo = min + qsz; --lo >= min;) { c = *lo; for (i = j = lo; (j -= qsz) >= hi; i = j) *i = *j; *i = c; } } } } /* * qst: Do a quicksort. First, find the median element, and put that one in * the first place as the discriminator. (This "median" is just the median * of the first, last and middle elements). (Using this median instead of * the first element is a big win). Then, the usual partitioning/swapping, * followed by moving the discriminator into the right place. Then, figure * out the sizes of the two partions, do the smaller one recursively and the * larger one via a repeat of this code. Stopping when there are less than * THRESH elements in a partition and cleaning up with an insertion sort (in * our caller) is a huge win. All data swaps are done in-line, which is * space-losing but time-saving. (And there are only three places where this * is done). */ static void #if STDC qst(char *base, char *max) #else qst(base, max) char *base; char *max; #endif { register char *i; register char *j; register char *jj; register char *mid; register int ii; register char c; char *tmp; int lo; int hi; lo = (int)(max - base); /* number of elements as chars */ do { /* * At the top here, lo is the number of characters of elements in the * current partition. (Which should be max - base). Find the median * of the first, last, and middle element and make that the middle * element. Set j to largest of first and middle. If max is larger * than that guy, then it's that guy, else compare max with loser of * first and take larger. Things are set up to prefer the middle, * then the first in case of ties. */ mid = i = base + qsz * ((unsigned) (lo / qsz) >> 1); if (lo >= mthresh) { j = ((*qcmp) ((jj = base), i) > 0 ? jj : i); if ((*qcmp) (j, (tmp = max - qsz)) > 0) { /* switch to first loser */ j = (j == jj ? i : jj); if ((*qcmp) (j, tmp) < 0) j = tmp; } if (j != i) { ii = qsz; do { c = *i; *i++ = *j; *j++ = c; } while (--ii); } } /* Semi-standard quicksort partitioning/swapping */ for (i = base, j = max - qsz;;) { while (i < mid && (*qcmp) (i, mid) <= 0) i += qsz; while (j > mid) { if ((*qcmp) (mid, j) <= 0) { j -= qsz; continue; } tmp = i + qsz; /* value of i after swap */ if (i == mid) { /* j <-> mid, new mid is j */ mid = jj = j; } else { /* i <-> j */ jj = j; j -= qsz; } goto swap; } if (i == mid) { break; } else { /* i <-> mid, new mid is i */ jj = mid; tmp = mid = i; /* value of i after swap */ j -= qsz; } swap: ii = qsz; do { c = *i; *i++ = *jj; *jj++ = c; } while (--ii); i = tmp; } /* * Look at sizes of the two partitions, do the smaller one first by * recursion, then do the larger one by making sure lo is its size, * base and max are update correctly, and branching back. But only * repeat (recursively or by branching) if the partition is of at * least size THRESH. */ i = (j = mid) + qsz; if ((lo = (int)(j - base)) <= (hi = (int)(max - i))) { if (lo >= thresh) qst(base, j); base = i; lo = hi; } else { if (hi >= thresh) qst(i, max); max = j; } } while (lo >= thresh); }