As far as I could check in Odoo 8, budget is established at input level by analytical account but I don't see the way to accumulate automatically budget in a view parent account. Is there a way to get budget automatic accumulation?

Additionally, we have made budget at product line level because we have many customers for the same product line so it would be impractical to budget at customer level. But when I'm trying to get a budget vs actual report at product line level (parent account), the field "Practical Amount" is always empty instead of showing the corresponding accumulated value. Does someone know how to get this accumulated value?