The corrected version of Qsort
Looks like I was copying the original Qsort from some where which contains a bug. But even that doesn't explain why it doesn't work on Paul's machine. Because I compiled the same thing and it works, for both debug and release.
Another test result:
std::sort using functor: 8938 ticks
std::sort using function: 8906 ticks
Qsort: 297 ticks
Here is the correct Qsort() function:
Code:
// This is Anthony's improved version of qsort -A.Mai 7/18/2002
void __cdecl Qsort (
void *base,
unsigned num,
unsigned width,
int (__cdecl *comp)(const void *, const void *)
)
{
char *lo, *hi;
char *mid;
char *loguy, *higuy;
unsigned size;
char *lostk[30], *histk[30];
int stkptr;
if (num < 2 || width == 0)
{
return;
}
stkptr = 0;
lo = (char*)base;
hi = (char *)base + width * (num-1);
recurse:
size = (hi - lo) / width + 1;
if (size > CUTOFF)
{
mid = lo + (size / 2) * width;
{
register int w2 = width;
if (w2 < 4)
{
do
{
char tmp;
w2 --;
tmp = mid[w2];
mid[w2] = lo[w2];
lo[w2] = tmp;
} while (w2 > 0);
}
else
{
int tmp;
tmp = *(int*)(&mid[w2-4]);
*(int*)(&mid[w2-4]) = *(int*)(&lo[w2-4]);
*(int*)(&lo[w2-4]) = tmp;
w2--;
w2 &= -4;
while (w2 >= 4)
{
w2 -= 4;
tmp = *(int*)(&mid[w2]);
*(int*)(&mid[w2]) = *(int*)(&lo[w2]);
*(int*)(&lo[w2]) = tmp;
}
}
}
loguy = lo;
higuy = hi + width;
for (;;)
{
do {
loguy += width;
} while (loguy <= hi && comp(loguy, lo) < 0); // <=
do {
higuy -= width;
} while (higuy > lo && comp(higuy, lo) > 0); // >=
if (higuy < loguy)
{
break;
}
{
register int w2 = width;
if (w2 < 4)
{
do
{
char tmp;
w2 --;
tmp = loguy[w2];
loguy[w2] = higuy[w2];
higuy[w2] = tmp;
} while (w2 > 0);
}
else
{
int tmp;
tmp = *(int*)(&loguy[w2-4]);
*(int*)(&loguy[w2-4]) = *(int*)(&higuy[w2-4]);
*(int*)(&higuy[w2-4]) = tmp;
w2--;
w2 &= -4;
while (w2 >= 4)
{
w2 -= 4;
tmp = *(int*)(&loguy[w2]);
*(int*)(&loguy[w2]) = *(int*)(&higuy[w2]);
*(int*)(&higuy[w2]) = tmp;
}
}
}
}
{
register int w2 = width;
if (w2 < 4)
{
do
{
char tmp;
w2 --;
tmp = lo[w2];
lo[w2] = higuy[w2];
higuy[w2] = tmp;
} while (w2 > 0);
}
else
{
int tmp;
tmp = *(int*)(&lo[w2-4]);
*(int*)(&lo[w2-4]) = *(int*)(&higuy[w2-4]);
*(int*)(&higuy[w2-4]) = tmp;
w2--;
w2 &= -4;
while (w2 >= 4)
{
w2 -= 4;
int tmp = *(int*)(&lo[w2]);
*(int*)(&lo[w2]) = *(int*)(&higuy[w2]);
*(int*)(&higuy[w2]) = tmp;
}
}
}
if ( higuy - 1 - lo >= hi - loguy )
{
if (lo + width < higuy)
{
lostk[stkptr] = lo;
histk[stkptr] = higuy - width;
++stkptr;
}
if (loguy < hi)
{
lo = loguy;
goto recurse;
}
}
else
{
if (loguy < hi)
{
lostk[stkptr] = loguy;
histk[stkptr] = hi;
++stkptr;
}
if (lo + width < higuy)
{
hi = higuy - width;
goto recurse;
}
}
}
else
{
char *p, *max;
while (hi > lo)
{
max = lo;
for (p = lo+width; p <= hi; p += width)
{
if (comp(p, max) > 0)
{
max = p;
}
}
if ( max != hi )
{
register int w2 = width;
if (w2 < 4)
{
do {
char tmp;
w2 --;
tmp = max[w2];
max[w2] = hi[w2];
hi[w2] = tmp;
} while (w2 > 0);
}
else
{
int tmp;
tmp = *(int*)(&max[w2-4]);
*(int*)(&max[w2-4]) = *(int*)(&hi[w2-4]);
*(int*)(&hi[w2-4]) = tmp;
w2--;
w2 &= -4;
while (w2 >= 4)
{
w2 -= 4;
tmp = *(int*)(&max[w2]);
*(int*)(&max[w2]) = *(int*)(&hi[w2]);
*(int*)(&hi[w2]) = tmp;
}
}
}
hi -= width;
}
}
--stkptr;
if (stkptr >= 0)
{
lo = lostk[stkptr];
hi = histk[stkptr];
goto recurse;
}
return;
}
