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In the MTD-f algorithm:

function MTDF(root : node_type; f : integer; d : integer) : integer;
    g := f;
    upperbound := +INFINITY;
    lowerbound := -INFINITY;
    repeat
        if g == lowerbound then beta := g + 1 else beta := g;
        g := AlphaBetaWithMemory(root, beta - 1, beta, d);
        if g < beta then upperbound := g else lowerbound := g;
    until lowerbound >= upperbound;
    return g;

Why exactly is this line: if g == lowerbound then beta := g + 1 else beta := g included, instead of just setting beta := g? Is it simply to ensure that once a lower bound is found, that the next calls to AlphaBetaWithMemory will return different/new results?

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