mat_dp_core.further_constraints

Constraints specify the conditions under which a system operates.
Mat-dp core exposes several types of constraint to help researchers assess systems under a variety of conditions.

Some examples:

• A given town will always consume water at 3,000 cubic metres/day: no more, no less.
  This can be expressed as an equal to (cycles == 3000) constraint.

• A certain cardboard factory will never produce any less than 4 tonnes of waste paper/day. This can be expressed as a greater than or equal to (cycles >= 4) constraint

• An energy firm has agreed to reduce its coal use, but to no less than 10 tonnes/day.
  This can be expressed as a less than or equal to (cycles <= -10) constraint.

Constraints make more sense in the context of the Objective; try to imagine how constraints are useful in describing a system in the context of your operational Objective.

The Three Constraints

There are three core Constraints, intended to be helpful in Mat-dp research contexts, these are: RunEqConstraint, RunRatioConstraint, and ResourceConstraint.

RunEqConstraint()

Summary:
Run Equal (to) Constraint states that a given process must run exactly n times.

Parameters:

• process process variable
  The process variable of choice.

• runs float
  A float value stating the number of runs this process should be constrained to do.

• name string
  A string representation of the constraint.

Return Type: RunEqConstraint

Location: further_constraints.py - class RunEqConstraint

Example Code:

from mat_dp_core import Resources, Processes, RunEqConstraint

r = Resources()
sandwich = r.create(name="sandwich", unit="ea")

p = Processes() 
cornerShop = p.create("corner shop", (sandwich, -1))

# corner shop always consumes 20 sandwiches
constraint = RunEqConstraint(cornerShop, 20, "Corner Shop Sandwich 20pcs constraint")

# For display purposes:
print(constraint)
"""
>>> <RunEqConstraint: Corner Shop Sandwich 20pcs constraint | Equation:corner shop == 20>
"""

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RunRatioConstraint()

Summary:
The Run Ratio Constraint class serves to fix the number of runs of a process in relation to another.
For example, a Wheel Factory may run at a fixed ratio to its corresponding Car Factory (4:1).

Parameters:

• process1 process variable
  The process to fix against another.

• process2 process variable
  The other process

• p2_over_p1 float
  A float value representing the fixed cycles of process1 vs process2

• name string
  A string representation of the constraint.

Return Type: RunRatioConstraint

Location: further_constraints.py - class RunRatioConstraint

Example Code:

from mat_dp_core import Resources, Processes, RunRatioConstraint

r = Resources()
flour = r.create(name="flour", unit="kilos")
bread = r.create(name="bread", unit="loaves")

p = Processes() 
flourMachine = p.create("flour maker", (flour, -0.7))
breadMachine = p.create("bread maker", (bread, 1))

constraint = RunRatioConstraint(flourMachine, breadMachine, 4, "fixed run ratio of bread to flour at 4:1")

# For display purposes:
print(constraint)
"""
>>> <RunRatioConstraint: fixed ratio of flour to bread at 4:1 | Equation:flour maker - 4*bread maker == 0>
"""

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ResourceConstraint()

Summary:
Sets the number runs of a process in relation to its production or consumption of a resource.
See the example code for more details.

Parameters:

• resource resource variable
  The resource variable to be constrained in its production or consumption.

• process process variable
  The process variable to be constrained.

• resource_bound float
  The float value give to the production or consumption a resource involved in this process.

• name string
  A string representation of the constraint.

Return Type: ResourceConstraint

Location: further_constraints.py - class ResourceConstraint

Example Code:

from mat_dp_core import Resources, Processes, ResourceConstraint

r = Resources()
flour = r.create(name="flour", unit="kilos")

p = Processes() 
flourMachine = p.create("flour maker", (flour, -0.7))

constraint = ResourceConstraint(resource=flour, process=flourMachine, resource_bound=4, name="Fixed output of flour at 4 units")

# For display purposes:
print(constraint)
"""
>>> <ResourceConstraint: Fixed output of flour at 4 units | Equation:flour maker == 5.714285714285714>
"""

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