5959 2016, Denver, CO, USA, pages 57-58, New York, NY, USA: ACM.
6060 ISBN: 978-1-4503-4323-7. https://doi.org/10.1145/2908961.2909001
6161"""
62- from typing import Callable , Final
62+ from typing import Final
6363
6464import numba # type: ignore
6565import numpy as np
6969
7070
7171@numba .njit (cache = True , inline = "always" , fastmath = True , boundscheck = False )
72- def try_single_rotate ( arr : np . ndarray , i1 : int , i2 : int ) -> bool : # +book
72+ def rotate ( random : Generator , dest : np . ndarray , x : np . ndarray ) -> None :
7373 """
74- Rotate a portion of an array to the left or right in place.
74+ Copy `x` into `dest` and then rotate a subsequence by one step.
75+
76+ The function repeatedly tries to rotate a portion of an array to the left
77+ or right in place. It will continue trying until something changed.
78+ In each step, it draws two indices `i1` and `i2`.
7579
7680 If `i1 < i2`, then a left rotation by one step is performed. In other
7781 words, the element at index `i1 + 1` goes to index `i1`, the element at
7882 index `i1 + 2` goes to index `i1 + 1`, and so on. The lst element, i.e.,
7983 the one at index `i2` goes to index `i2 - 1`. Finally, the element that
8084 originally was at index `i1` goes to index `i2`. If any element in the
81- array has changed, this function returns `False` , otherwise `True` .
85+ array has changed, this function is done , otherwise it tries again .
8286
8387 If `i1 > i2`, then a right rotation by one step is performed. In other
8488 words, the element at index `i1 - 1` goes to index `i1`, the element at
8589 index `i1 - 2` goes to index `i1 - 1`, and so on. Finally, the element
8690 that originally was at index `i1` goes to index `i2`. If any element in
87- the array has changed, this function returns `False` , otherwise `True` .
91+ the array has changed, this function tries again , otherwise it stops .
8892
8993 This corresponds to extracting the element at index `i1` and re-inserting
9094 it at index `i2`.
9195
92- :param arr: the array to rotate
93- :param i1: the start index, in `0..len(arr)-1`
94- :param i2: the end index, in `0..len(arr)-1`
95- :returns: whether the array was *unchanged*
96- :retval False: if the array `arr` is now different from before
97- :retval True: if the array `arr` has not changed
98-
99- >>> import numpy as npx
100- >>> dest = npx.array(range(10))
101- >>> print(dest)
102- [0 1 2 3 4 5 6 7 8 9]
103- >>> try_single_rotate(dest, 3, 4)
104- False
105- >>> print(dest)
106- [0 1 2 4 3 5 6 7 8 9]
107- >>> try_single_rotate(dest, 3, 4)
108- False
109- >>> print(dest)
110- [0 1 2 3 4 5 6 7 8 9]
111- >>> try_single_rotate(dest, 4, 3)
112- False
113- >>> print(dest)
114- [0 1 2 4 3 5 6 7 8 9]
115- >>> try_single_rotate(dest, 4, 3)
116- False
117- >>> print(dest)
118- [0 1 2 3 4 5 6 7 8 9]
119- >>> try_single_rotate(dest, 3, 6)
120- False
121- >>> print(dest)
122- [0 1 2 4 5 6 3 7 8 9]
123- >>> try_single_rotate(dest, 6, 3)
124- False
125- >>> print(dest)
126- [0 1 2 3 4 5 6 7 8 9]
127- >>> try_single_rotate(dest, 0, len(dest) - 1)
128- False
129- >>> print(dest)
130- [1 2 3 4 5 6 7 8 9 0]
131- >>> try_single_rotate(dest, len(dest) - 1, 0)
132- False
133- >>> print(dest)
134- [0 1 2 3 4 5 6 7 8 9]
135- >>> try_single_rotate(dest, 7, 7)
136- True
137- >>> dest = np.array([0, 1, 2, 3, 3, 3, 3, 3, 8, 9])
138- >>> try_single_rotate(dest, 7, 7)
139- True
140- >>> try_single_rotate(dest, 4, 6)
141- True
142- >>> print(dest)
143- [0 1 2 3 3 3 3 3 8 9]
144- >>> try_single_rotate(dest, 6, 4)
145- True
146- >>> print(dest)
147- [0 1 2 3 3 3 3 3 8 9]
148- >>> try_single_rotate(dest, 4, 7)
149- True
150- >>> print(dest)
151- [0 1 2 3 3 3 3 3 8 9]
152- >>> try_single_rotate(dest, 6, 7)
153- True
154- >>> print(dest)
155- [0 1 2 3 3 3 3 3 8 9]
156- >>> try_single_rotate(dest, 4, 8)
157- False
158- >>> print(dest)
159- [0 1 2 3 3 3 3 8 3 9]
160- >>> try_single_rotate(dest, 8, 4)
161- False
162- >>> print(dest)
163- [0 1 2 3 3 3 3 3 8 9]
164- >>> try_single_rotate(dest, 9, 4)
165- False
166- >>> print(dest)
167- [0 1 2 3 9 3 3 3 3 8]
168- >>> try_single_rotate(dest, 4, 9)
169- False
170- >>> print(dest)
171- [0 1 2 3 3 3 3 3 8 9]
172- """
173- # start book
174- if i1 == i2 : # nothing to be done
175- return True # array will not be changed
176-
177- unchanged : bool = True # initially, assume that there is no change
178-
179- if i1 < i2 : # rotate to the left: move elements to lower indices?
180- first = arr [i1 ] # get the element to be removed
181- while i1 < i2 : # iterate the indices
182- i3 = i1 + 1 # get next higher index
183- cpy = arr [i3 ] # get next element at that higher index
184- unchanged = unchanged and (cpy == arr [i1 ]) # is a change?
185- arr [i1 ] = cpy # store next element at the lower index
186- i1 = i3 # move to next higher index
187- unchanged = unchanged and (first == arr [i2 ]) # check if change
188- arr [i2 ] = first # store removed element at highest index
189- return unchanged # return True if something changed, else False
190-
191- last = arr [i1 ] # last element; rotate right: move elements up
192- while i2 < i1 : # iterate over indices
193- i3 = i1 - 1 # get next lower index
194- cpy = arr [i3 ] # get element at that lower index
195- unchanged = unchanged and (cpy == arr [i1 ]) # is a change?
196- arr [i1 ] = cpy # store element at higher index
197- i1 = i3 # move to next lower index
198- unchanged = unchanged and (last == arr [i2 ]) # check if change
199- arr [i2 ] = last # store removed element at lowest index
200- return unchanged # return True if something changed, else False
201- # end book
202-
203-
204- # Temporary fix for https://github.com/numba/numba/issues/9103
205- def rotate (random : Generator , dest : np .ndarray , # +book
206- x : np .ndarray ) -> None : # +book
207- """
208- Copy `x` into `dest` and then rotate a subsequence by one step.
209-
21096 :param random: the random number generator
21197 :param dest: the array to receive the modified copy of `x`
21298 :param x: the existing point in the search space
@@ -227,14 +113,37 @@ def rotate(random: Generator, dest: np.ndarray, # +book
227113 >>> print(out)
228114 [0 1 2 3 4 8 5 6 7 9]
229115 """
230- # start book
231116 dest [:] = x [:]
232117 length : Final [int ] = len (dest ) # Get the length of `dest`.
233- rint : Callable [[int , int ], int ] = random .integers # fast call
234-
118+ unchanged : bool = True
235119 # try to rotate the dest array until something changes
236- while try_single_rotate (dest , rint (0 , length ), rint (0 , length )):
237- pass # do nothing in the loop, but try rotating again
120+ while unchanged :
121+ i1 : int = random .integers (0 , length )
122+ i2 : int = random .integers (0 , length )
123+ if i1 == i2 : # nothing to be done
124+ continue # array will not be changed
125+
126+ if i1 < i2 : # rotate to the left: move elements to lower indices?
127+ first = dest [i1 ] # get the element to be removed
128+ while i1 < i2 : # iterate the indices
129+ i3 = i1 + 1 # get next higher index
130+ cpy = dest [i3 ] # get next element at that higher index
131+ unchanged &= (cpy == dest [i1 ]) # is a change?
132+ dest [i1 ] = cpy # store next element at the lower index
133+ i1 = i3 # move to next higher index
134+ unchanged &= (first == dest [i2 ]) # check if change
135+ dest [i2 ] = first # store removed element at highest index
136+ continue
137+
138+ last = dest [i1 ] # last element; rotate right: move elements up
139+ while i2 < i1 : # iterate over indices
140+ i3 = i1 - 1 # get next lower index
141+ cpy = dest [i3 ] # get element at that lower index
142+ unchanged &= (cpy == dest [i1 ]) # is a change?
143+ dest [i1 ] = cpy # store element at higher index
144+ i1 = i3 # move to next lower index
145+ unchanged &= (last == dest [i2 ]) # check if change
146+ dest [i2 ] = last # store removed element at lowest index
238147
239148
240149class Op1Insert1 (Op1 ):
@@ -254,7 +163,6 @@ def __init__(self) -> None:
254163 """Initialize the object."""
255164 super ().__init__ ()
256165 self .op1 = rotate # type: ignore # use function directly
257- # end book
258166
259167 def __str__ (self ) -> str :
260168 """
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