NPTEL_notes

Question

Consider the expression : ((a ∗ (b ∗ c)) ∗ (d + (e + f ))) + ((g + (h + i )) + (j ∗ (k ∗ l)))

1. what is the minimum number of register required to evaluate this expression if intermediate results are not stored in memory?

2. Using algebraic properties of the operators rearrange the tree obtained in the first question and find the minimum number of registers required for this tree?

When to use sethi-ullman algorithm and when not? Is it a feasible option to find the minimum number of register required to evaluate three address code?

Comments

answer to first question is 4 ! what about next ?

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Using algebraic properties of the operators rearrange

I don't understand that what is the need to rearrange?

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after re-arrangement using properties of operator it required only 2 registers that's why!

@MiNiPanda when can we use sethi-ullman and when not do you have any idea?