Topic
• 2 replies
• Latest Post - ‏2013-10-01T14:37:10Z by qtbgo
qtbgo
134 Posts

# Pinned topic units of resource change over time

‏2013-10-01T08:22:48Z |

Hi, suppose we have a type of resource , the number of it changes over time t, this can be expressed by an array  n[t in 0..T]. For example, in time 0-1, n[0] =10 (we have 10 units of resource);  time 1-2, n[1] = 9; time 2-3, n[2] = 11,...

Activities (interval variables) a[i in 1..N] in 0..T+1 will consume this resource.

I want that:

at any time t , the number of resources consumed by activities should not exceed n[t].

How to express this constraint? I tried cumulative function, but failed.

Any help is appreciated.

• rdumeur
78 Posts

#### Re: units of resource change over time

‏2013-10-01T11:51:51Z

Dear qtbgo,

In order to constrain the cumul function representing the varying usage of your resource, you should use the alwaysIn constraint:

http://pic.dhe.ibm.com/infocenter/cosinfoc/v12r5/index.jsp

you must create, for your cumul function, an alwaysIn constraint for each interval in "n".

Did you use this constraint in your model?

I hope this helps.

Cheers,

• rdumeur
78 Posts

#### Re: units of resource change over time

‏2013-10-01T11:51:51Z

Dear qtbgo,

In order to constrain the cumul function representing the varying usage of your resource, you should use the alwaysIn constraint:

http://pic.dhe.ibm.com/infocenter/cosinfoc/v12r5/index.jsp

you must create, for your cumul function, an alwaysIn constraint for each interval in "n".

Did you use this constraint in your model?

I hope this helps.

Cheers,

• qtbgo
134 Posts

#### Re: units of resource change over time

‏2013-10-01T14:37:10Z
• rdumeur
• ‏2013-10-01T11:51:51Z

Dear qtbgo,

In order to constrain the cumul function representing the varying usage of your resource, you should use the alwaysIn constraint:

http://pic.dhe.ibm.com/infocenter/cosinfoc/v12r5/index.jsp

you must create, for your cumul function, an alwaysIn constraint for each interval in "n".

Did you use this constraint in your model?

I hope this helps.

Cheers,

Thank you very much, rdumeur. It works.