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Add intro sort to Array #3514

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merged 3 commits into from
Nov 17, 2016
Merged

Add intro sort to Array #3514

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b589800
Add intro sort to Array
c910335 Nov 6, 2016
416a421
Use center median instead of shift median
c910335 Nov 7, 2016
ca094a2
Fix center median
c910335 Nov 16, 2016
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216 changes: 184 additions & 32 deletions src/array.cr
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Original file line number Diff line number Diff line change
Expand Up @@ -1484,12 +1484,12 @@ class Array(T)
# Optionally, a block may be given that must implement a comparison, either with the comparison operator `<=>`
# or a comparison between *a* and *b*, where a < b yields -1, a == b yields 0, and a > b yields 1.
def sort!
Array.quicksort!(@buffer, @size)
Array.intro_sort!(@buffer, @size)
self
end

def sort!(&block : T, T -> Int32)
Array.quicksort!(@buffer, @size, block)
Array.intro_sort!(@buffer, @size, block)
self
end

Expand Down Expand Up @@ -1717,48 +1717,200 @@ class Array(T)
end
end

protected def self.quicksort!(a, n, comp)
return if (n < 2)
p = a[n / 2]
l = a
r = a + n - 1
while l <= r
if comp.call(l.value, p) < 0
l += 1
elsif comp.call(r.value, p) > 0
r -= 1
protected def self.intro_sort!(a, n)
return if n < 2
quick_sort_for_intro_sort!(a, n, Math.log2(n).to_i * 2)
insertion_sort!(a, n)
end

protected def self.quick_sort_for_intro_sort!(a, n, d)
while n > 16
if d == 0
heap_sort!(a, n)
return
end
d -= 1
center_median!(a, n)
c = partition_for_quick_sort!(a, n)
quick_sort_for_intro_sort!(c, n - (c - a), d)
n = c - a
end
end

protected def self.heap_sort!(a, n)
(n / 2).downto 0 do |p|
heapify!(a, p, n)
end
while n > 1
n -= 1
a.value, a[n] = a[n], a.value
heapify!(a, 0, n)
end
end

protected def self.heapify!(a, p, n)
v, c = a[p], p
while c < (n - 1) / 2
c = 2 * (c + 1)
c -= 1 if a[c] < a[c - 1]
break unless v <= a[c]
a[p] = a[c]
p = c
end
if n & 1 == 0 && c == n / 2 - 1
c = 2 * c + 1
if v < a[c]
a[p] = a[c]
p = c
end
end
a[p] = v
end

protected def self.center_median!(a, n)
b, c = a + n / 2, a + n - 1
if a.value <= b.value
if b.value <= c.value
return
elsif a.value <= c.value
b.value, c.value = c.value, b.value
else
t = l.value
l.value = r.value
l += 1
r.value = t
r -= 1
a.value, b.value, c.value = c.value, a.value, b.value
end
elsif a.value <= c.value
a.value, b.value = b.value, a.value
elsif b.value <= c.value
a.value, b.value, c.value = b.value, c.value, a.value
else
a.value, c.value = c.value, a.value
end
quicksort!(a, (r - a) + 1, comp) unless r == a + n - 1
quicksort!(l, (a + n) - l, comp) unless l == a
end

protected def self.quicksort!(a, n)
return if (n < 2)
p = a[n / 2]
l = a
r = a + n - 1
while l <= r
if l.value < p
protected def self.partition_for_quick_sort!(a, n)
v, l, r = a[n / 2], a + 1, a + n - 1
loop do
while l.value < v
l += 1
elsif r.value > p
end
r -= 1
while v < r.value
r -= 1
end
return l unless l < r
l.value, r.value = r.value, l.value
l += 1
end
end

protected def self.insertion_sort!(a, n)
(1...n).each do |i|
l = a + i
v = l.value
p = l - 1
while l > a && v < p.value
l.value = p.value
l, p = p, p - 1
end
l.value = v
end
end

protected def self.intro_sort!(a, n, comp)
return if n < 2
quick_sort_for_intro_sort!(a, n, Math.log2(n).to_i * 2, comp)
insertion_sort!(a, n, comp)
end

protected def self.quick_sort_for_intro_sort!(a, n, d, comp)
while n > 16
if d == 0
heap_sort!(a, n, comp)
return
end
d -= 1
center_median!(a, n, comp)
c = partition_for_quick_sort!(a, n, comp)
quick_sort_for_intro_sort!(c, n - (c - a), d, comp)
n = c - a
end
end

protected def self.heap_sort!(a, n, comp)
(n / 2).downto 0 do |p|
heapify!(a, p, n, comp)
end
while n > 1
n -= 1
a.value, a[n] = a[n], a.value
heapify!(a, 0, n, comp)
end
end

protected def self.heapify!(a, p, n, comp)
v, c = a[p], p
while c < (n - 1) / 2
c = 2 * (c + 1)
c -= 1 if comp.call(a[c], a[c - 1]) < 0
break unless comp.call(v, a[c]) <= 0
a[p] = a[c]
p = c
end
if n & 1 == 0 && c == n / 2 - 1
c = 2 * c + 1
if comp.call(v, a[c]) < 0
a[p] = a[c]
p = c
end
end
a[p] = v
end

protected def self.center_median!(a, n, comp)
b, c = a + n / 2, a + n - 1
if comp.call(a.value, b.value) <= 0
if comp.call(b.value, c.value) <= 0
return
elsif comp.call(a.value, c.value) <= 0
b.value, c.value = c.value, b.value
else
t = l.value
l.value = r.value
a.value, b.value, c.value = c.value, a.value, b.value
end
elsif comp.call(a.value, c.value) <= 0
a.value, b.value = b.value, a.value
elsif comp.call(b.value, c.value) <= 0
a.value, b.value, c.value = b.value, c.value, a.value
else
a.value, c.value = c.value, a.value
end
end

protected def self.partition_for_quick_sort!(a, n, comp)
v, l, r = a[n / 2], a + 1, a + n - 1
loop do
while comp.call(l.value, v) < 0
l += 1
r.value = t
end
r -= 1
while comp.call(v, r.value) < 0
r -= 1
end
return l unless l < r
l.value, r.value = r.value, l.value
l += 1
end
end

protected def self.insertion_sort!(a, n, comp)
(1...n).each do |i|
l = a + i
v = l.value
p = l - 1
while l > a && comp.call(v, p.value) < 0
l.value = p.value
l, p = p, p - 1
end
l.value = v
end
quicksort!(a, (r - a) + 1) unless r == a + n - 1
quicksort!(l, (a + n) - l) unless l == a
end

protected def to_lookup_hash
Expand Down