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Munkres
Module munkres :: Class Munkres
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Class Munkres

source code

Calculate the Munkres solution to the classical assignment problem. See the module documentation for usage.
Instance Methods [hide private]
 
__init__(self)
Create a new instance		 source code
list of lists
pad_matrix(self, matrix, pad_value=0)
Pad a possibly non-square matrix to make it square.		 source code
list
compute(self, cost_matrix)
Compute the indexes for the lowest-cost pairings between rows and columns in the database. Returns a list of (row, column) tuples that can be used to traverse the matrix.		 source code
 
__copy_matrix(self, matrix)
Return an exact copy of the supplied matrix		 source code
 
__make_matrix(self, n, val)
Create an n*x*n matrix, populating it with the specific value.		 source code
 
__step1(self)
For each row of the matrix, find the smallest element and subtract it from every element in its row. Go to Step 2.		 source code
 
__step2(self)
Find a zero (Z) in the resulting matrix. If there is no starred zero in its row or column, star Z. Repeat for each element in the matrix. Go to Step 3.		 source code
 
__step3(self)
Cover each column containing a starred zero. If K columns are covered, the starred zeros describe a complete set of unique assignments. In this case, Go to DONE, otherwise, Go to Step 4.		 source code
 
__step4(self)
Find a noncovered zero and prime it. If there is no starred zero in the row containing this primed zero, Go to Step 5. Otherwise, cover this row and uncover the column containing the starred zero. Continue in this manner until there are no uncovered zeros left. Save the smallest uncovered value and Go to Step 6.		 source code
 
__step5(self)
Construct a series of alternating primed and starred zeros as follows. Let Z0 represent the uncovered primed zero found in Step 4. Let Z1 denote the starred zero in the column of Z0 (if any). Let Z2 denote the primed zero in the row of Z1 (there will always be one). Continue until the series terminates at a primed zero that has no starred zero in its column. Unstar each starred zero of the series, star each primed zero of the series, erase all primes and uncover every line in the matrix. Return to Step 3		 source code
 
__step6(self)
Add the value found in Step 4 to every element of each covered row, and subtract it from every element of each uncovered column. Return to Step 4 without altering any stars, primes, or covered lines.		 source code
 
__find_smallest(self)
Find the smallest uncovered value in the matrix.		 source code
 
__find_a_zero(self)
Find the first uncovered element with value 0		 source code
 
__find_star_in_row(self, row)
Find the first starred element in the specified row. Returns the column index, or -1 if no starred element was found.		 source code
 
__find_star_in_col(self, col)
Find the first starred element in the specified row. Returns the row index, or -1 if no starred element was found.		 source code
 
__find_prime_in_row(self, row)
Find the first prime element in the specified row. Returns the column index, or -1 if no starred element was found.		 source code
 
__convert_path(self, path, count) source code
 
__clear_covers(self)
Clear all covered matrix cells		 source code
 
__erase_primes(self)
Erase all prime markings		 source code
Static Methods [hide private]
 
make_cost_matrix(profit_matrix, inversion_function)
DEPRECATED		 source code
Method Details [hide private]

make_cost_matrix(profit_matrix, inversion_function)
Static Method

source code 

DEPRECATED

Please use the module function make_cost_matrix().

pad_matrix(self, matrix, pad_value=0)

source code 
Pad a possibly non-square matrix to make it square.
Parameters:
  • matrix (list of lists) - matrix to pad
  • pad_value (int) - value to use to pad the matrix
Returns: list of lists
a new, possibly padded, matrix

compute(self, cost_matrix)

source code 
Compute the indexes for the lowest-cost pairings between rows and columns in the database. Returns a list of (row, column) tuples that can be used to traverse the matrix.
Parameters:

  • cost_matrix (list of lists) - The cost matrix. If this cost matrix is not square, it will be padded with zeros, via a call to pad_matrix(). (This method does not modify the caller's matrix. It operates on a copy of the matrix.)

    WARNING: This code handles square and rectangular matrices. It does not handle irregular matrices.

Returns: list
A list of (row, column) tuples that describe the lowest cost path through the matrix

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Munkres
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