304 lines
10 KiB
Python
304 lines
10 KiB
Python
import collections
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import itertools
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import operator
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import heapq
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import copy
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from .pack_algo import PackingAlgorithm
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from .geometry import Point as P
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from .geometry import HSegment, Rectangle
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from .waste import WasteManager
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class Skyline(PackingAlgorithm):
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""" Class implementing Skyline algorithm as described by
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Jukka Jylanki - A Thousand Ways to Pack the Bin (February 27, 2010)
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_skyline: stores all the segments at the top of the skyline.
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_waste: Handles all wasted sections.
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"""
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def __init__(self, width, height, rot=True, *args, **kwargs):
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"""
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_skyline is the list used to store all the skyline segments, each
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one is a list with the format [x, y, width] where x is the x
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coordinate of the left most point of the segment, y the y coordinate
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of the segment, and width the length of the segment. The initial
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segment is allways [0, 0, surface_width]
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Arguments:
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width (int, float):
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height (int, float):
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rot (bool): Enable or disable rectangle rotation
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"""
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self._waste_management = False
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self._waste = WasteManager(rot=rot)
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super(Skyline, self).__init__(width, height, rot, merge=False, *args, **kwargs)
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def _placement_points_generator(self, skyline, width):
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"""Returns a generator for the x coordinates of all the placement
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points on the skyline for a given rectangle.
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WARNING: In some cases could be duplicated points, but it is faster
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to compute them twice than to remove them.
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Arguments:
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skyline (list): Skyline HSegment list
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width (int, float): Rectangle width
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Returns:
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generator
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"""
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skyline_r = skyline[-1].right
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skyline_l = skyline[0].left
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# Placements using skyline segment left point
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ppointsl = (s.left for s in skyline if s.left+width <= skyline_r)
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# Placements using skyline segment right point
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ppointsr = (s.right-width for s in skyline if s.right-width >= skyline_l)
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# Merge positions
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return heapq.merge(ppointsl, ppointsr)
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def _generate_placements(self, width, height):
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"""
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Generate a list with
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Arguments:
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skyline (list): SkylineHSegment list
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width (number):
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Returns:
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tuple (Rectangle, fitness):
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Rectangle: Rectangle in valid position
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left_skyline: Index for the skyline under the rectangle left edge.
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right_skyline: Index for the skyline under the rectangle right edte.
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"""
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skyline = self._skyline
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points = collections.deque()
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left_index = right_index = 0 # Left and right side skyline index
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support_height = skyline[0].top
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support_index = 0
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placements = self._placement_points_generator(skyline, width)
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for p in placements:
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# If Rectangle's right side changed segment, find new support
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if p+width > skyline[right_index].right:
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for right_index in range(right_index+1, len(skyline)):
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if skyline[right_index].top >= support_height:
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support_index = right_index
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support_height = skyline[right_index].top
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if p+width <= skyline[right_index].right:
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break
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# If left side changed segment.
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if p >= skyline[left_index].right:
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left_index +=1
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# Find new support if the previous one was shifted out.
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if support_index < left_index:
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support_index = left_index
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support_height = skyline[left_index].top
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for i in range(left_index, right_index+1):
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if skyline[i].top >= support_height:
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support_index = i
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support_height = skyline[i].top
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# Add point if there is enought room at the top
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if support_height+height <= self.height:
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points.append((Rectangle(p, support_height, width, height),\
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left_index, right_index))
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return points
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def _merge_skyline(self, skylineq, segment):
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"""
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Arguments:
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skylineq (collections.deque):
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segment (HSegment):
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"""
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if len(skylineq) == 0:
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skylineq.append(segment)
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return
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if skylineq[-1].top == segment.top:
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s = skylineq[-1]
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skylineq[-1] = HSegment(s.start, s.length+segment.length)
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else:
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skylineq.append(segment)
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def _add_skyline(self, rect):
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"""
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Arguments:
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seg (Rectangle):
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"""
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skylineq = collections.deque([]) # Skyline after adding new one
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for sky in self._skyline:
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if sky.right <= rect.left or sky.left >= rect.right:
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self._merge_skyline(skylineq, sky)
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continue
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if sky.left < rect.left and sky.right > rect.left:
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# Skyline section partially under segment left
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self._merge_skyline(skylineq,
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HSegment(sky.start, rect.left-sky.left))
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sky = HSegment(P(rect.left, sky.top), sky.right-rect.left)
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if sky.left < rect.right:
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if sky.left == rect.left:
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self._merge_skyline(skylineq,
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HSegment(P(rect.left, rect.top), rect.width))
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# Skyline section partially under segment right
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if sky.right > rect.right:
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self._merge_skyline(skylineq,
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HSegment(P(rect.right, sky.top), sky.right-rect.right))
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sky = HSegment(sky.start, rect.right-sky.left)
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if sky.left >= rect.left and sky.right <= rect.right:
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# Skyline section fully under segment, account for wasted space
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if self._waste_management and sky.top < rect.bottom:
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self._waste.add_waste(sky.left, sky.top,
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sky.length, rect.bottom - sky.top)
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else:
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# Segment
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self._merge_skyline(skylineq, sky)
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# Aaaaand ..... Done
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self._skyline = list(skylineq)
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def _rect_fitness(self, rect, left_index, right_index):
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return rect.top
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def _select_position(self, width, height):
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"""
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Search for the placement with the bes fitness for the rectangle.
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Returns:
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tuple (Rectangle, fitness) - Rectangle placed in the fittest position
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None - Rectangle couldn't be placed
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"""
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positions = self._generate_placements(width, height)
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if self.rot and width != height:
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positions += self._generate_placements(height, width)
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if not positions:
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return None, None
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return min(((p[0], self._rect_fitness(*p))for p in positions),
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key=operator.itemgetter(1))
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def fitness(self, width, height):
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"""Search for the best fitness
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"""
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assert(width > 0 and height >0)
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if width > max(self.width, self.height) or\
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height > max(self.height, self.width):
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return None
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# If there is room in wasted space, FREE PACKING!!
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if self._waste_management:
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if self._waste.fitness(width, height) is not None:
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return 0
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# Get best fitness segment, for normal rectangle, and for
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# rotated rectangle if rotation is enabled.
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rect, fitness = self._select_position(width, height)
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return fitness
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def add_rect(self, width, height, rid=None):
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"""
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Add new rectangle
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"""
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assert(width > 0 and height > 0)
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if width > max(self.width, self.height) or\
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height > max(self.height, self.width):
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return None
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rect = None
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# If Waste managment is enabled, first try to place the rectangle there
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if self._waste_management:
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rect = self._waste.add_rect(width, height, rid)
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# Get best possible rectangle position
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if not rect:
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rect, _ = self._select_position(width, height)
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if rect:
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self._add_skyline(rect)
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if rect is None:
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return None
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# Store rectangle, and recalculate skyline
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rect.rid = rid
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self.rectangles.append(rect)
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return rect
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def reset(self):
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super(Skyline, self).reset()
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self._skyline = [HSegment(P(0, 0), self.width)]
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self._waste.reset()
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class SkylineWMixin(Skyline):
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"""Waste managment mixin"""
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def __init__(self, width, height, *args, **kwargs):
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super(SkylineWMixin, self).__init__(width, height, *args, **kwargs)
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self._waste_management = True
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class SkylineMwf(Skyline):
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"""Implements Min Waste fit heuristic, minimizing the area wasted under the
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rectangle.
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"""
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def _rect_fitness(self, rect, left_index, right_index):
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waste = 0
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for seg in self._skyline[left_index:right_index+1]:
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waste +=\
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(min(rect.right, seg.right)-max(rect.left, seg.left)) *\
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(rect.bottom-seg.top)
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return waste
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def _rect_fitnes2s(self, rect, left_index, right_index):
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waste = ((min(rect.right, seg.right)-max(rect.left, seg.left)) for seg in self._skyline[left_index:right_index+1])
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return sum(waste)
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class SkylineMwfl(Skyline):
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"""Implements Min Waste fit with low profile heuritic, minimizing the area
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wasted below the rectangle, at the same time it tries to keep the height
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minimal.
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"""
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def _rect_fitness(self, rect, left_index, right_index):
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waste = 0
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for seg in self._skyline[left_index:right_index+1]:
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waste +=\
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(min(rect.right, seg.right)-max(rect.left, seg.left)) *\
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(rect.bottom-seg.top)
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return waste*self.width*self.height+rect.top
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class SkylineBl(Skyline):
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"""Implements Bottom Left heuristic, the best fit option is that which
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results in which the top side of the rectangle lies at the bottom-most
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position.
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"""
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def _rect_fitness(self, rect, left_index, right_index):
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return rect.top
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class SkylineBlWm(SkylineBl, SkylineWMixin):
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pass
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class SkylineMwfWm(SkylineMwf, SkylineWMixin):
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pass
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class SkylineMwflWm(SkylineMwfl, SkylineWMixin):
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pass
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