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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
define LOGPTR 32 # log2(maxpts) (4e9)
# ASRT -- Vector Quicksort. The output vector may be the same as the
# input vector.
procedure asrtl (a, b, npix)
long a[ARB], b[ARB] # input, output arrays
int npix # number of pixels
long pivot, temp
int i, j, k, p, lv[LOGPTR], uv[LOGPTR]
define swap {temp=$1;$1=$2;$2=temp}
begin
call amovl (a, b, npix) # in place sort
lv[1] = 1
uv[1] = npix
p = 1
while (p > 0) {
if (lv[p] >= uv[p]) # only one elem in this subset
p = p - 1 # pop stack
else {
# Dummy do loop to trigger the Fortran optimizer.
do p = p, ARB {
i = lv[p] - 1
j = uv[p]
# Select as the pivot the element at the center of the
# array, to avoid quadratic behavior on an already sorted
# array.
k = (lv[p] + uv[p]) / 2
swap (b[j], b[k])
pivot = b[j] # pivot line
while (i < j) {
for (i=i+1; b[i] < pivot; i=i+1)
;
for (j=j-1; j > i; j=j-1)
if (b[j] <= pivot)
break
if (i < j) # out of order pair
swap (b[i], b[j]) # interchange elements
}
j = uv[p] # move pivot to position i
swap (b[i], b[j]) # interchange elements
if (i-lv[p] < uv[p] - i) { # stack so shorter done first
lv[p+1] = lv[p]
uv[p+1] = i - 1
lv[p] = i + 1
} else {
lv[p+1] = i + 1
uv[p+1] = uv[p]
uv[p] = i - 1
}
break
}
p = p + 1 # push onto stack
}
}
end
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