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Examples for support purposes...

https://pypi.python.org/pypi/glpk

import glpk
help(glpk)
Help on module glpk: NAME glpk FILE /usr/local/sage/sage-6.4/local/lib/python2.7/site-packages/glpk.so DESCRIPTION The PyGLPK module, encapsulating the functionality of the GNU Linear Programming Kit. Usage of this module will typically start with the initialization of an LPX instance to define a linear program, and proceed from there to add data to the problem and ultimately solve it. See help on the LPX class, as well as the HTML documentation accompanying your PyGLPK distribution. CLASSES __builtin__.object Bar BarCollection BarCollectionIter Environment KKT LPX Objective ObjectiveIter Tree TreeIter TreeNode class Bar(__builtin__.object) | Bar objects are used to refer to a particular row or column of | a linear program. Rows and columns may be retrieved by | indexing into the rows and cols sequences of LPX instances. | | Methods defined here: | | __eq__(...) | x.__eq__(y) <==> x==y | | __ge__(...) | x.__ge__(y) <==> x>=y | | __gt__(...) | x.__gt__(y) <==> x>y | | __le__(...) | x.__le__(y) <==> x<=y | | __lt__(...) | x.__lt__(y) <==> x<y | | __ne__(...) | x.__ne__(y) <==> x!=y | | __repr__(...) | x.__repr__() <==> repr(x) | | __str__(...) | x.__str__() <==> str(x) | | ---------------------------------------------------------------------- | Data descriptors defined here: | | bounds | The lower and upper bounds, where None signifies unboundedness. | | dual | The dual value of this variable by the last solver. | | dual_i | The dual value of this variable by the interior-point solver. | | dual_s | The dual value of this variable by the simplex solver. | | index | The index of the row or column this object refers to. | | iscol | Whether this is a column. | | isrow | Whether this is a row. | | kind | Either the type 'float' if this is a continuous variable, 'int' | if this is an integer variable, or 'bool' if this is a binary | variable. | | matrix | Non-zero constraint coefficients in this row/column vector | as a list of two-element (index, value) tuples. | | name | Row/column symbolic name, or None if unset. | | nnz | Number of non-zero constraint elements in this row/column. | | primal | The primal value of this variable by the last solver. | | primal_i | The primal value of this variable by the interior-point solver. | | primal_s | The primal value of this variable by the simplex solver. | | scale | The scale for the row or column. This is a factor which one may | set to improve conditioning in the problem. Most users will want | to use the LPX.scale() method rather than setting these directly. | The resulting constraint matrix is such that the entry at row i | and column j is (for the purpose of optimization) (ri)*(aij)*(sj) | where ri and sj are the row and column scaling factors, and aij | is the entry of the constraint matrix. | | status | Row/column basis status. This is a two character string with | the following possible values: | | bs -- This row/column is basic. | nl -- This row/column is non-basic. | nu -- This row/column is non-basic and set to the upper bound. | On assignment, if this row/column is not double bounded, | this is equivalent to 'nl'. | nf -- This row/column is non-basic and free. | On assignment this is equivalent to 'nl'. | ns -- This row/column is non-basic and fixed. | On assignment this is equivalent to 'nl'. | | valid | Whether this row or column has a valid index in its LP. | | value | The value of this variable by the last solver. | | value_m | The value of this variable by the MIP solver. class BarCollection(__builtin__.object) | Bar collection objects. An instance is used to index into either | the rows and columns of a linear program. They exist as the 'rows' | and 'cols' attributes of LPX instances. | | One accesses particular rows or columns by indexing the appropriate | bar collection object, or iterating over it. Valid indices include | particular row and column names (a user defined string) or numbers | (counting from 0), a slice specifying a range of numeric elements, | or a series of individual indices. For example, for an LPX instance | lp, we may have: | | lp.rows[0] --> the first row | lp.rows[-1] --> the last row | lp.cols[:3] --> the first three columns | lp.cols[1,'name',5] --> column 1, a column named 'name', and column 5 | | One may also query the length of this sequence to get the number of | rows or columns, and del to get rid of rows or columns, e.g.: | | len(lp.cols) --> the number of columns in the problem | del lp.rows['arow'] --> deletes a row named 'arow' | del lp.rows[-2:] --> deletes the last two rows | | Methods defined here: | | __contains__(...) | x.__contains__(y) <==> y in x | | __delitem__(...) | x.__delitem__(y) <==> del x[y] | | __getitem__(...) | x.__getitem__(y) <==> x[y] | | __iter__(...) | x.__iter__() <==> iter(x) | | __len__(...) | x.__len__() <==> len(x) | | __setitem__(...) | x.__setitem__(i, y) <==> x[i]=y | | __str__(...) | x.__str__() <==> str(x) | | add(...) | add(n) | | Add n more rows (constraints) or columns (struct variables). | Returns the index of the first added entry. class BarCollectionIter(__builtin__.object) | Bar collection iterator objects. Created for iterating over the | rows and columns contained with a bar collection. | | Methods defined here: | | __getattribute__(...) | x.__getattribute__('name') <==> x.name | | __iter__(...) | x.__iter__() <==> iter(x) | | __len__(...) | x.__len__() <==> len(x) | | next(...) | x.next() -> the next value, or raise StopIteration class Environment(__builtin__.object) | This represents the PyGLPK environment. Through this, one may control | the global behavior of the GLPK. One instance of this exists, named | env in the glpk module. | | Data descriptors defined here: | | blocks | The number of currently allocated memory blocks. | | blocks_peak | The peak value of the blocks attribute. | | bytes | The number of currently allocated memory bytes. | | bytes_peak | The peak value of the bytes attribute. | | mem_limit | The memory limit in megabytes. None if no limit is set. | | term_hook | Function to intercept all terminal output. This should be a | callable object that accepts a single string argument, or None | to indicate that no hook is set (e.g., all output goes to the | terminal, default behavior). Note that when the function is | called, there is no guarantee that the input string will be a | full line, or even non-empty. All exceptions thrown by the | function will go ignored and unreported. | | term_on | Whether or not terminal output for the underlying GLPK | procedures is on or off. | | version | Tuple holding the major version and minor version of the GLPK | that this PyGLPK module was built upon. For example, if built | against GLPK 4.31, version==(4,31). class KKT(__builtin__.object) | Karush-Kuhn-Tucker conditions. This is returned from a check on | quality of solutions. Four types of conditions are stored here: | - KKT.PE conditions are attributes prefixed by 'pe' measuring | error in the primal solution. | - KKT.PB conditions are attributes prefixed by 'pb' measuring | error in satisfying primal bound constraints, i.e., feasibility. | - KKT.DE and KKT.DB are analogous, but for the dual. | | Data descriptors defined here: | | db_ae_ind | Index of the variable with the largest absolute error. | | db_ae_max | Largest absolute error. | | db_quality | Character representing the quality of primal feasibility. | 'H', high, 'M', medium, 'L', low, or '?' wrong or infeasible. | | db_re_ind | Index of the variable with the largest relative error. | | db_re_max | Largest relative error. | | de_ae_max | Largest absolute error. | | de_ae_row | Index of the column with the largest absolute error. | | de_quality | Character representing the quality of the primal solution. | 'H', high, 'M', medium, 'L', low, or '?' wrong or infeasible. | | de_re_max | Largest relative error. | | de_re_row | Index of the column with the largest relative error. | | pb_ae_ind | Index of the variable with the largest absolute error. | | pb_ae_max | Largest absolute error. | | pb_quality | Character representing the quality of primal feasibility. | 'H', high, 'M', medium, 'L', low, or '?' wrong or infeasible. | | pb_re_ind | Index of the variable with the largest relative error. | | pb_re_max | Largest relative error. | | pe_ae_max | Largest absolute error. | | pe_ae_row | Index of the row with the largest absolute error. | | pe_quality | Character representing the quality of the primal solution. | 'H', high, 'M', medium, 'L', low, or '?' wrong or infeasible. | | pe_re_max | Largest relative error. | | pe_re_row | Index of the row with the largest relative error. class LPX(__builtin__.object) | LPX() --> Empty linear program. | LPX(gmp=filename) --> Linear program with data read from a | GNU MathProg file containing model and data. | LPX(mps=filename) --> Linear program with data read from a | datafile in fixed MPS format. | LPX(freemps=filename) --> Linear program with data read from a | datafile in free MPS format. | LPX(cpxlp=filename) --> Linear program with data read from a | datafile in fixed CPLEX LP format. | LPX(glp=filename) --> Linear program with data read from a | datafile in GNU LP format. | LPX(gmp=(model_filename,[data_filename,[output_filename]])--> | Linear program from GNU MathProg input files. The first | element is a path to the model second, the second to the | data section. If the second element is omitted or is None | then the model file is presumed to also hold the data. | The third elment holds the output data file to write | display statements to. If omitted or None, the output | is instead put through to standard output. | | This represents a linear program object. It holds data and | offers methods relevant to the whole of the linear program. | There are many members in this class, but the most important | are: | obj Represents the objective function. | rows A collection over which one can access rows. | cols Same, but for columns. | | Methods defined here: | | __init__(...) | x.__init__(...) initializes x; see help(type(x)) for signature | | __repr__(...) | x.__repr__() <==> repr(x) | | __str__(...) | x.__str__() <==> str(x) | | adv_basis(...) | adv_basis() | | Construct an advanced initial basis, triangular with as few | variables as possible fixed. | | cpx_basis(...) | cpx_basis() | | Construct an advanced Bixby basis. | | This basis construction method is described in: | Robert E. Bixby. Implementing the Simplex Method: The Initial | Basis. ORSA Journal on Computing, Vol. 4, No. 3, 1992, | pp. 267-84. | | erase(...) | erase() | | Erase the content of this problem, restoring it to the state | it was in when it was first created. | | exact(...) | exact() | | Attempt to solve the problem using an exact simplex method. | | This returns None if the problem was successfully solved. | Alternately, on failure it will return one of the following | strings to indicate failure type. | | fault -- There are no rows or columns, or the initial basis | is invalid, or the initial basis matrix is singular | or ill-conditioned. | itlim -- Iteration limited exceeded. | tmlim -- Time limit exceeded. | | integer(...) | integer() | | MIP solver based on branch-and-bound. | | This procedure has a great number of optional keyword arguments | to control the functioning of the solver. We list these here, | including descriptions of their legal values. | | msg_lev : Controls the message level of terminal output. | LPX.MSG_OFF -- no output (default) | LPX.MSG_ERR -- error and warning messages | LPX.MSG_ON -- normal output | LPX.MSG_ALL -- full informational output | br_tech : Branching technique option. | LPX.BR_FFV -- first fractional variable | LPX.BR_LFV -- last fractional variable | LPX.BR_MFV -- most fractional variable | LPX.BR_DTH -- heuristic by Driebeck and Tomlin (default) | bt_tech : Backtracking technique option. | LPX.BT_DFS -- depth first search | LPX.BT_BFS -- breadth first search | LPX.BT_BLB -- best local bound (default) | LPX.BT_BPH -- best projection heuristic | pp_tech : Preprocessing technique option. | LPX.PP_NONE -- disable preprocessing | LPX.PP_ROOT -- perform preprocessing only on the root level | LPX.PP_ALL -- perform preprocessing on all levels (default) | gmi_cuts: Use Gomory's mixed integer cuts (default False) | mir_cuts: Use mixed integer rounding cuts (default False) | tol_int : Tolerance used to check if the optimal solution to the | current LP relaxation is integer feasible. | tol_obj : Tolerance used to check if the objective value in the | optimal solution to the current LP is not better than the best | known integer feasible solution. | tm_lim : Search time limit in milliseconds. (default is max int) | out_frq : Terminal output frequency in milliseconds. (default 5000) | out_dly : Terminal output delay in milliseconds. (default 10000) | callback: A callback object the user may use to monitor and control | the solver. During certain portions of the optimization, the | solver will call methods of callback object. (default None) | | The last parameter, callback, is worth its own discussion. During | the branch-and-cut algorithm of the MIP solver, at various points | callback hooks are invoked which allow the user code to influence | the proceeding of the MIP solver. The user code may influence the | solver in the hook by modifying and operating on a Tree instance | passed to the hook. These hooks have various codes, which we list | here. | select - request for subproblem selection | prepro - request for preprocessing | rowgen - request for row generation | heur - request for heuristic solution | cutgen - request for cut generation | branch - request for branching | bingo - better integer solution found | During the invocation of a hook with a particular code, the | callback object will have a method of the same name as the hook | code called, with the Tree instance. For instance, for the | 'cutgen' hook, it is equivalent to | callback.cutgen(tree) | being called with tree as the Tree instance. If the method does | not exist, then instead the method 'default' is called with the | same signature. If neither the named hook method nor the default | method exist, then the hook is ignored. | | This method requires a mixed-integer problem where an optimal | solution to an LP relaxation (either through simplex() or | exact()) has already been found. Alternately, try intopt(). | | This returns None if the problem was successfully solved. | Alternately, on failure it will return one of the following | strings to indicate failure type. | | fault -- There are no rows or columns, or it is not a MIP | problem, or integer variables have non-int bounds. | nopfs -- No primal feasible solution. | nodfs -- Relaxation has no dual feasible solution. | itlim -- Iteration limited exceeded. | tmlim -- Time limit exceeded. | sing -- Error occurred solving an LP relaxation subproblem. | | interior(...) | interior() | | Attempt to solve the problem using an interior-point method. | | This returns None if the problem was successfully solved. | Alternately, on failure it will return one of the following | strings to indicate failure type. | | fault -- There are no rows or columns. | nofeas -- The problem has no feasible (primal/dual) solution. | noconv -- Very slow convergence or divergence. | itlim -- Iteration limited exceeded. | instab -- Numerical instability when solving Newtonian system. | | intopt(...) | intopt() | | More advanced MIP branch-and-bound solver than integer(). This | variant does not require an existing LP relaxation. | | This returns None if the problem was successfully solved. | Alternately, on failure it will return one of the following | strings to indicate failure type. | | fault -- There are no rows or columns, or it is not a MIP | problem, or integer variables have non-int bounds. | nopfs -- No primal feasible solution. | nodfs -- Relaxation has no dual feasible solution. | itlim -- Iteration limited exceeded. | tmlim -- Time limit exceeded. | sing -- Error occurred solving an LP relaxation subproblem. | | kkt(...) | kkt([scaled=False]) | | Return an object encapsulating the results of a check on the | Karush-Kuhn-Tucker optimality conditions for a basic (simplex) | solution. If the argument 'scaled' is true, return results | of checking the internal scaled instance of the LP instead. | | kktint(...) | kktint() | | Similar to kkt(), except analyzes solution quality of an | mixed-integer solution. Note that only the primal components | of the KKT object will have meaningful values. | | read_basis(...) | read_basis(filename) | | Reads an LP basis in the fixed MPS format from a given file. | | scale(...) | scale([flags=LPX.SF_AUTO]) | | Perform automatic scaling of the problem data, in order to. | improve conditioning. The behavior is controlled by various | flags, which can be bitwise ORed to combine effects. Note | that this only affects the internal state of the LP | representation. These flags are members of the LPX class: | | SF_GM -- perform geometric mean scaling | SF_EQ -- perform equilibration scaling | SF_2N -- round scale factors to the nearest power of two | SF_SKIP -- skip scaling, if the problem is well scaled | SF_AUTO -- choose scaling options automatically | | simplex(...) | simplex([keyword arguments]) | | Attempt to solve the problem using a simplex method. | | This procedure has a great number of optional keyword arguments | to control the functioning of the solver. We list these here, | including descriptions of their legal values. | | msg_lev : Controls the message level of terminal output. | LPX.MSG_OFF -- no output (default) | LPX.MSG_ERR -- error and warning messages | LPX.MSG_ON -- normal output | LPX.MSG_ALL -- full informational output | meth : Simplex method option | LPX.PRIMAL -- use two phase primal simplex (default) | LPX.DUAL -- use two phase dual simplex | LPX.DUALP -- use two phase dual simplex, primal if that fails | pricing : Pricing technique | LPX.PT_STD -- standard textbook technique | LPX.PT_PSE -- projected steepest edge (default) | r_test : Ratio test technique | LPX.RT_STD -- standard textbook technique | LPX.RT_HAR -- Harris' two-pass ratio test (default) | tol_bnd : Tolerance used to check if the basic solution is primal | feasible. (default 1e-7) | tol_dj : Tolerance used to check if the basic solution is dual | feasible. (default 1e-7) | tol_piv : Tolerance used to choose pivotal elements of the simplex | table. (default 1e-10) | obj_ll : Lower limit of the objective function. The solver | terminates upon reaching this level. This is used only in | dual simplex optimization. (default is min float) | obj_ul : Upper limit of the objective function. The solver | terminates upon reaching this level. This is used only in | dual simplex optimization. (default is max float) | it_lim : Simplex iteration limit. (default is max int) | tm_lim : Search time limit in milliseconds. (default is max int) | out_frq : Terminal output frequency in iterations. (default 200) | out_dly : Terminal output delay in milliseconds. (default 0) | presolve: Use the LP presolver. (default False) | | This returns None if the problem was successfully solved. | Alternately, on failure it will return one of the following | strings to indicate failure type. | | fault -- There are no rows or columns, or the initial basis | is invalid, or the initial basis matrix is singular | or ill-conditioned. | objll -- The objective reached its lower limit. | objul -- The objective reached its upper limit. | itlim -- Iteration limited exceeded. | tmlim -- Time limit exceeded. | sing -- The basis matrix became singular or ill-conditioned. | nopfs -- No primal feasible solution. (Presolver only.) | nodfs -- No dual feasible solution. (Presolver only.) | | std_basis(...) | std_basis() | | Construct the standard trivial inital basis for this LP. | | unscale(...) | unscale() | | This unscales the problem data, essentially setting all | scale factors to 1. | | write(...) | write(format=filename) | | Output data about the linear program into a file with a given | format. What data is written, and how it is written, depends | on which of the format keywords are used. Note that one may | specify multiple format and filename pairs to write multiple | types and formats of data in one call to this function. | | mps -- For problem data in the fixed MPS format. | bas -- The current LP basis in fixed MPS format. | freemps -- Problem data in the free MPS format. | cpxlp -- Problem data in the CPLEX LP format. | glp -- Problem data in the GNU LP format. | prob -- Problem data in a plain text format. | sol -- Basic solution in printable format. | sens_bnds -- Bounds sensitivity information. | ips -- Interior-point solution in printable format. | mip -- MIP solution in printable format. | | ---------------------------------------------------------------------- | Data descriptors defined here: | | cols | Column collection. See the help on class BarCollection. | | kind | Either the type 'float' if this is a pure linear programming | (LP) problem, or the type 'int' if this is a mixed integer | programming (MIP) problem. | | matrix | The constraint matrix as a list of three element (row index, | column index, value) tuples across all non-zero elements of | the constraint matrix. | | name | Problem name, or None if unset. | | nbin | The number of binary column variables, i.e., integer with 0 | to 1 bounds. Always 0 if this is not a mixed integer problem. | | nint | The number of integer column variables. Always 0 if this is | not a mixed integer problem. | | nnz | Number of non-zero constraint coefficients. | | obj | Objective function object. | | ray | A non-basic row or column the simplex solver has identified | as causing primal unboundness, or None if no such variable | has been identified. | | rows | Row collection. See the help on class BarCollection. | | status | The status of solution of the last solver. This takes the | form of a string with these possible values. | | opt -- The solution is optimal. | undef -- The solution is undefined. | feas -- The solution is feasible, but not necessarily optimal. | infeas -- The solution is infeasible. | nofeas -- The problem has no feasible solution. | unbnd -- The problem has an unbounded solution. | | status_dual | The status of the dual solution of the simplex solver. | Possible values are 'undef', 'feas', 'infeas', 'nofeas' in | similar meaning to the .status attribute. | | status_i | The status of the interior point solver's solution. | | status_m | The status of the MIP solver's solution. | | status_primal | The status of the primal solution of the simplex solver. | Possible values are 'undef', 'feas', 'infeas', 'nofeas' in | similar meaning to the .status attribute. | | status_s | The status of the simplex solver's solution. | | ---------------------------------------------------------------------- | Data and other attributes defined here: | | BR_DTH = 4 | | BR_FFV = 1 | | BR_LFV = 2 | | BR_MFV = 3 | | BT_BFS = 2 | | BT_BLB = 3 | | BT_BPH = 4 | | BT_DFS = 1 | | DUAL = 3 | | DUALP = 2 | | MSG_ALL = 3 | | MSG_ERR = 1 | | MSG_OFF = 0 | | MSG_ON = 2 | | PP_ALL = 2 | | PP_NONE = 0 | | PP_ROOT = 1 | | PRIMAL = 1 | | PT_PSE = 34 | | PT_STD = 17 | | RT_HAR = 34 | | RT_STD = 17 | | SF_2N = 32 | | SF_AUTO = 128 | | SF_EQ = 16 | | SF_GM = 1 | | SF_SKIP = 64 | | __new__ = <built-in method __new__ of type object> | T.__new__(S, ...) -> a new object with type S, a subtype of T class Objective(__builtin__.object) | Objective function objects for linear programs. An instance is | used either to access objective function values for solutions, | or to access or set objective function coefficients. The same | indices valid for a BarCollection object over the columns | (that is, column numeric indices, column names, slices, | multiple values) are also valid for indexing into this object. | The special index None is used to specify the shift term. If | we have an LPX instance lp, we may have: | | lp.obj[0] --> the first objective coefficient | lp.obj[None] --> the shift term | lp.obj[-3:] --> the last three objective coefficients | | lp.obj[1,4] --> the objective coefficients 1, 4 | When assigning objective coefficients, for single indices one | may assign a single number. For multiple indices, one may | assign a single number to make all indicated coefficients | identical, or specify an iterable of equal length to set them | all individiaully. For example: | | lp.obj[0]=2.5 --> set the first objective coef to 2.5 | lp.obj[-3:]=1.0 --> the last three obj coefs get 1.0 | lp.obj[1,4]=-2.0,2.0 --> obj coefs 1, 4 get -2.0, 2.0 | | Methods defined here: | | __delitem__(...) | x.__delitem__(y) <==> del x[y] | | __getitem__(...) | x.__getitem__(y) <==> x[y] | | __iter__(...) | x.__iter__() <==> iter(x) | | __len__(...) | x.__len__() <==> len(x) | | __setitem__(...) | x.__setitem__(i, y) <==> x[i]=y | | ---------------------------------------------------------------------- | Data descriptors defined here: | | maximize | True or False depending on whether we are trying to maximize | or minimize this objective function, respectively. | | name | Objective name, or None if unset. | | shift | The constant shift term of the objective function. | | value | The current value of the objective function. | | value_i | The current value of the interior point objective function. | | value_m | The current value of the MIP objective function. | | value_s | The current value of the simplex objective function. class ObjectiveIter(__builtin__.object) | Objective function iterator objects, used to cycle over the | coefficients of the objective function. | | Methods defined here: | | __getattribute__(...) | x.__getattribute__('name') <==> x.name | | __iter__(...) | x.__iter__() <==> iter(x) | | __len__(...) | x.__len__() <==> len(x) | | next(...) | x.next() -> the next value, or raise StopIteration class Tree(__builtin__.object) | Tree instances are passed to MIP solver callback function. They | are used to indicate the state of the solver at some intermediate | point in a call to LPX.integer(). There are nodes within the | tree, instances of TreeNode, corresponding to subproblems within | the search tree. The currently active subproblem is stored in | the curr_node member of an instance. | | Methods defined here: | | __iter__(...) | x.__iter__() <==> iter(x) | | branch_upon(...) | branch_upon(col_index, select='N') | | Given the index of a column in the LP, this will add two | new subproblems, down and up branches (in that order) to the | active list, where the down and up branches are the problems | with the column's variable set to the floor and ceil of the | value, respectively. The select parameter controls which | of the two branches is selected to next continue the search | with 'D', 'U', and 'N' corresponding to choosing the down, | up, or letting GLPK select a branch, respectively. | | can_branch(...) | can_branch(col_index) | | Given the index of a column in the LP, this will return True | if one can branch upon this column's varible, that is, | continue the search with this column's variable set as an | integer. Note that this function should be called only when | the reason member of the tree is 'branch'. | | heuristic(...) | heuristic(values) | | Provide an integer feasible solution of the primal problem, | where values is an iterable object yielding at least as many | float values as there are columns in the problem. If the | provided solution is better than the existing one, the | solution is accepted and the problem updated. This function | returns True or False depending on whether the solution was | accepted or not. Note that this function should be called | only when the reason member of the tree is 'heur'. | | select(...) | select(node) | | Selects a tree node to continue search from. Note that this | function should be called only when the reason member of the | tree is 'select'. | | terminate(...) | terminate() | | Prematurely terminate the MIP solver's search. | | ---------------------------------------------------------------------- | Data descriptors defined here: | | best_node | The node of the current active subproblem with best local bound. | If the tree is empty, this is None. | | curr_node | The node of the current active subproblem. If there is no current | active subproblem in the tree, this will return None. | | first_node | The node of the first active subproblem. If there is no current | active subproblem in the tree, this is None. | | gap | The relative MIP gap (duality gap), that is, the gap between the | best MIP solution (best_mip) and best relaxed solution (best_bnd) | given by this formula: | |best_mip - best_bnd| | gap = --------------------- | |best_mip|+epsilon | | last_node | The node of the last active subproblem. If there is no current | active subproblem in the tree, this is None. | | lp | Problem object used by the MIP solver. | | num_active | The number of active nodes. | | num_all | The number of all nodes, both active and inactive. | | num_total | The total number of nodes, including those already removed. | | reason | A string with the reason the callback function has been called. class TreeIter(__builtin__.object) | Tree iterator objects. Created for iterating over the | active subproblems of the search tree. | | Methods defined here: | | __getattribute__(...) | x.__getattribute__('name') <==> x.name | | __iter__(...) | x.__iter__() <==> iter(x) | | next(...) | x.next() -> the next value, or raise StopIteration class TreeNode(__builtin__.object) | TreeNode instances represent specific subproblem instances in the | search Tree object used by the MIP solver. | | Methods defined here: | | __eq__(...) | x.__eq__(y) <==> x==y | | __ge__(...) | x.__ge__(y) <==> x>=y | | __gt__(...) | x.__gt__(y) <==> x>y | | __le__(...) | x.__le__(y) <==> x<=y | | __lt__(...) | x.__lt__(y) <==> x<y | | __ne__(...) | x.__ne__(y) <==> x!=y | | __repr__(...) | x.__repr__() <==> repr(x) | | __str__(...) | x.__str__() <==> str(x) | | ---------------------------------------------------------------------- | Data descriptors defined here: | | active | Whether this node represents an active subproblem. | | bound | The local bound for this node's subproblem. | | level | The level of the node in the tree, with 0 if this is the root. | | next | The next active subproblem node, None if there is no next active | subproblem, or if this is not an active subproblem. | | prev | The previous active subproblem node, None if there is no previous | active subproblem, or if this is not an active subproblem. | | subproblem | The reference number of the subproblem corresponding to this node. | | up | The parent subproblem node, None if this is the root. DATA env = <glpk.Environment object>