This example implements a column generation approach to solve the cutting stock problem. More...

Variables
str	cutstock.GAMS_MASTER_MODEL

str	cutstock.GAMS_SUB_MODEL

sys	cutstock.sys_dir = sys.argv[1] if len(sys.argv) > 1 else None

GamsWorkspace	cutstock.ws = GamsWorkspace(system_directory=sys_dir)

GamsWorkspace	cutstock.opt = ws.add_options()

GamsWorkspace	cutstock.cutstock_data = ws.add_database("csdata")

	cutstock.all_model_types

	cutstock.optcr

int	cutstock.max_pattern = 35

int	cutstock.r = 100

GamsWorkspace	cutstock.raw_width = cutstock_data.add_parameter("r", 0, "raw width")

	cutstock.value

dict	cutstock.d = {"i1": 97, "i2": 610, "i3": 395, "i4": 211}

GamsWorkspace	cutstock.demand = cutstock_data.add_parameter("d", 1, "demand")

GamsWorkspace	cutstock.widths = cutstock_data.add_set("i", 1, "widths")

dict	cutstock.w = {"i1": 47, "i2": 36, "i3": 31, "i4": 14}

GamsWorkspace	cutstock.width = cutstock_data.add_parameter("w", 1, "width")

GamsWorkspace	cutstock.cp_master = ws.add_checkpoint()

GamsWorkspace	cutstock.job_master_init = ws.add_job_from_string(GAMS_MASTER_MODEL)

	cutstock.databases

GamsWorkspace	cutstock.job_master

GamsWorkspace	cutstock.pattern = cutstock_data.add_set("pp", 1, "pattern index")

GamsWorkspace	cutstock.pattern_data = cutstock_data.add_parameter("aip", 2, "pattern data")

int	cutstock.pattern_count = 0

GamsWorkspace	cutstock.cp_sub = ws.add_checkpoint()

GamsWorkspace	cutstock.job_sub = ws.add_job_from_string(GAMS_SUB_MODEL)

GamsWorkspace	cutstock.mi_sub = cp_sub.add_modelinstance()

GamsWorkspace	cutstock.demand_dual

	cutstock.else :

GamsWorkspace	cutstock.s = pattern.add_record(str(pattern_count))

GamsWorkspace	cutstock.aip = job_master.out_db["aip"].first_record((" ", xp.key(0)))

Detailed Description

This example implements a column generation approach to solve the cutting stock problem.

In this example, the column generation approach has been entirely implemented in the program using GamsJob for the master and GamsModelInstance for the pricing problem. GAMS is used to build the master and pricing problems. The logic of the column generation method is in the application program.

Definition in file cutstock.py.

Variables

Detailed Description