algorithms-python/algorithms/sort/bitonic_sort.py at master · ivan1911/algorithms-python · GitHub

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def bitonic_sort(arr, reverse=False):

"""

bitonic sort is sorting algorithm to use multiple process, but this code not containing parallel process

It can sort only array that sizes power of 2

It can sort array in both increasing order and decreasing order by giving argument true(increasing) and false(decreasing)

Worst-case in parallel: O(log(n)^2)

Worst-case in non-parallel: O(nlog(n)^2)

reference: https://en.wikipedia.org/wiki/Bitonic_sorter

"""

def compare(arr, reverse):

n = len(arr)//2

for i in range(n):

if reverse != (arr[i] > arr[i+n]):

arr[i], arr[i+n] = arr[i+n], arr[i]

return arr

def bitonic_merge(arr, reverse):

n = len(arr)

if n <= 1:

return arr

arr = compare(arr, reverse)

left = bitonic_merge(arr[:n // 2], reverse)

right = bitonic_merge(arr[n // 2:], reverse)

return left + right

#end of function(compare and bitionic_merge) definition

n = len(arr)

if n <= 1:

return arr

# checks if n is power of two

if not (n and (not(n & (n - 1))) ):

raise ValueError("the size of input should be power of two")

left = bitonic_sort(arr[:n // 2], True)

right = bitonic_sort(arr[n // 2:], False)

arr = bitonic_merge(left + right, reverse)

return arr

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