Calculating ? (cont.)

r1 = (?u/?x) 2 +(?v/?x)2

r2 = (?u/?y) 2 +(?v/?y)2

requires two multiplications and an addition for each.

Finally,

? = log2(max(sqrt(r1), sqrt(r2)))

= log2(sqrt(max(r1,r2)))

= 0.5 * log2 (max (r1,r2))

= log2 (max (r1,r2)) >> 1 (shift right by one)

log2 is not an easy calculation if you need an accurate fractional part (which we do).