Talk:Common subexpression elimination

Template:WikiProject banner shell This problem seems much more complicated than the article suggests. For example,

$x^{3} + 3 x^{2} y + 3 x y^{2} + y^{3} - x^{2} - 2 x y + 2 x c - y^{2} + 2 y c - c^{2}$

takes 19 multiplications and 9 additions to evaluate, but it can be rewritten as

$(x + y)^{3} + (x + y - c)^{2}$

which only requires 3 multiplications and 3 additions. How does subexpression elimination know how to do this?

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