【发布时间】：2014-05-25 20:30:21
【问题描述】：
我在 Python 方面面临着一个令人惊讶的挑战。
我是一名物理学家，在光学接口处生成一系列层模拟。模拟的细节并不是特别重要，但关键是我生成了所有可能的情况——在一定厚度和层序范围内的不同材料。
我一直在编写代码来生成一个全面而独特的列表，但我对计算即使是相对简单的系统也需要多长时间感到震惊！当然，Python 和一台合理的计算机应该可以在没有过多压力的情况下处理这个问题。建议将不胜感激。
谢谢
from itertools import permutations, combinations_with_replacement
def join_adjacent_repeated_materials(potential_structure):
"""
Self-explanitory...
"""
#print potential_structure
new_layers = [] # List to hold re-cast structure
for layer in potential_structure:
if len(new_layers) > 0: # if not the first item in the list of layers
last_layer=new_layers[-1] # last element of existing layer list
if layer[0] == last_layer[0]: # true is the two layers are the same material
combined_layer = (layer[0], layer[1] + last_layer[1])
new_layers[len(new_layers)-1] = combined_layer
else: # adjcent layers are different material so no comibantion is possible
new_layers.append(layer)
else: # for the first layer
new_layers.append(layer)
return tuple(new_layers)
def calculate_unique_structure_lengths(thicknesses, materials, maximum_number_of_layers,\
maximum_individual_layer_thicknesses, \
maximum_total_material_thicknesses):
"""
Create a set on all possible multilayer combinations.
thicknesses : if this contains '0' the total number of layers will vary
from 0 to maximum_number_of_layers, otherwise, the
number total number layers will always be maximum_number_of_layers
e.g. arange(0 , 100, 5)
materials : list of materials used
e.g. ['Metal', 'Dielectric']
maximum_number_of_layers : pretty self-explanitory...
e.g. 5
maximum_individual_layer_thicknesses : filters the created the multilayer structures
preventing the inclusion layers that are too thick
- this is important after the joining of
adjacent materials
e.g. (('Metal',30),('Dielectric',20))
maximum_total_material_thicknesses : similar to the above but filters structures where the total
amount of a particular material is exceeded
e.g. (('Metal',50),('Dielectric',100))
"""
# generate all possible thickness combinations and material combinations
all_possible_thickness_sets = set(permutations(combinations_with_replacement(thicknesses, maximum_number_of_layers)))
all_possible_layer_material_orders = set(permutations(combinations_with_replacement(materials, maximum_number_of_layers)))
first_set = set() # Create set object (list of unique elements, no repeats)
for layer_material_order in all_possible_layer_material_orders:
for layer_thickness_set in all_possible_thickness_sets:
potential_structure = [] # list to hold this structure
for layer, thickness in zip(layer_material_order[0], layer_thickness_set[0]): # combine the layer thickness with its material
if thickness != 0: # layers of zero thickness are not added to potential_structure
potential_structure.append((layer, thickness))
first_set.add(tuple(potential_structure)) # add this potential_structure to the first_set set
#print('first_set')
#for struct in first_set:
# print struct
## join adjacent repeated materials
second_set = set() # create new set
for potential_structure in first_set:
second_set.add(join_adjacent_repeated_materials(potential_structure))
## remove structures where a layer is too thick
third_set = set()
for potential_structure in second_set: # check all the structures in the set
conditions_satisfied=True # default
for max_condition in maximum_individual_layer_thicknesses: # check this structure using each condition
for layer in potential_structure: # examine each layer
if layer[0] == max_condition[0]: # match condition with material
if layer[1] > max_condition[1]: # test thickness condition
conditions_satisfied=False
if conditions_satisfied:
third_set.add(potential_structure)
##remove structures that contain too much of a certain material
fourth_set = set()
for potential_structure in second_set: # check all the structures in the set
conditions_satisfied=True # default
for max_condition in maximum_total_material_thicknesses: # check this structure using each condition
amount_of_material_in_this_structure = 0 # initialise a counter
for layer in potential_structure: # examine each layer
if layer[0] == max_condition[0]: # match condition with material
amount_of_material_in_this_structure += layer[1]
if amount_of_material_in_this_structure > max_condition[1]: # test thickness condition
conditions_satisfied=False
if conditions_satisfied:
fourth_set.add(potential_structure)
return fourth_set
thicknesses = [0,1,2]
materials = ('A', 'B') # Tuple cannot be accidentally appended to later
maximum_number_of_layers = 3
maximum_individual_layer_thicknesses=(('A',30),('B',20))
maximum_total_material_thicknesses=(('A',20),('B',15))
calculate_unique_structure_lengths(thicknesses, materials, maximum_number_of_layers,\
maximum_individual_layer_thicknesses = maximum_individual_layer_thicknesses, \
maximum_total_material_thicknesses = maximum_total_material_thicknesses)
【问题讨论】：
-
您能否更具体一点：代码的哪些部分很慢，如果可能，我们如何重现缓慢的行为？您是否也尝试过自己分析代码？如果你有，你能给我们提供结果吗？
-
分析您的代码并查看其大部分时间花在哪里。