Dummy imports are a great tool when setting up models. They act as a safety net, helping you identify infeasibilities and oversights without debilitating your model. There’s nothing more frustrating than a model that doesn’t solve - and dummy imports can reduce these dead ends.
But like any safety net, it’s one you could get entangled in if you’re not careful. As models grow more complex, it’s possible for filter oversights to cause dummy imports to inherit unintended parameters and behave in unexpected ways. For example, a dummy import could accidentally pick up an AF(LO), or get tied to a growth constraint - leading to arbitrary flows that are hard to diagnose and can mask deeper issues.
**Two actions can help:
1. Check dummy imports in Items view.
When mysterious dummy flows appear, review them in Items view. This will help confirm whether the dummy import process has inherited unintended parameters (like AF, bounds, or growth constraints). It’s a fast way to spot specification errors that might otherwise take a long time to track down.
2. Confirm that the dummy-imported commodity has a high shadow price.
If the dummy import is active, check the shadow price of the commodity in the relevant period. A high shadow price confirms that the commodity is genuinely short - and that the dummy import is serving its intended purpose and not serving the ACT variable with an arbitrary choice.
These simple checks will help ensure that your dummy imports remain a useful aid - without becoming a source of mysteries.
But like any safety net, it’s one you could get entangled in if you’re not careful. As models grow more complex, it’s possible for filter oversights to cause dummy imports to inherit unintended parameters and behave in unexpected ways. For example, a dummy import could accidentally pick up an AF(LO), or get tied to a growth constraint - leading to arbitrary flows that are hard to diagnose and can mask deeper issues.
**Two actions can help:
1. Check dummy imports in Items view.
When mysterious dummy flows appear, review them in Items view. This will help confirm whether the dummy import process has inherited unintended parameters (like AF, bounds, or growth constraints). It’s a fast way to spot specification errors that might otherwise take a long time to track down.
2. Confirm that the dummy-imported commodity has a high shadow price.
If the dummy import is active, check the shadow price of the commodity in the relevant period. A high shadow price confirms that the commodity is genuinely short - and that the dummy import is serving its intended purpose and not serving the ACT variable with an arbitrary choice.
These simple checks will help ensure that your dummy imports remain a useful aid - without becoming a source of mysteries.