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Long division is the standard algorithm used for pen-and-paper division of multi-digit numbers expressed in decimal notation. It shifts gradually from the left to the right end of the dividend, subtracting the largest possible multiple of the divisor (at the digit level) at each stage; the multiples then become the digits of the quotient, and the final difference is then the remainder.
The elementary functions are constructed by composing arithmetic operations, the exponential function (), the natural logarithm (), trigonometric functions (,), and their inverses. The complexity of an elementary function is equivalent to that of its inverse, since all elementary functions are analytic and hence invertible by means of Newton's ...
Many programming languages provide functions that can be used to divide a floating point number by a power of two. For example, the Java programming language provides the method java.lang.Math.scalb for scaling by a power of two, [7] and the C programming language provides the function ldexp for the same purpose. [8]
The smallest counterexample is for a power of 15, when the binary method needs six multiplications. Instead, form x 3 in two multiplications, then x 6 by squaring x 3 , then x 12 by squaring x 6 , and finally x 15 by multiplying x 12 and x 3 , thereby achieving the desired result with only five multiplications.
This method is an efficient variant of the 2 k-ary method. For example, to calculate the exponent 398, which has binary expansion (110 001 110) 2, we take a window of length 3 using the 2 k-ary method algorithm and calculate 1, x 3, x 6, x 12, x 24, x 48, x 49, x 98, x 99, x 198, x 199, x 398.
This efficiency can be described by the number of division steps the algorithm requires, multiplied by the computational expense of each step. The first known analysis of Euclid's algorithm is due to A. A. L. Reynaud in 1811, [87] who showed that the number of division steps on input (u, v) is bounded by v; later he improved this to v/2 + 2
Decimal numbers are not divided directly, the dividend and divisor are multiplied by a power of ten so that the division involves two whole numbers. Therefore, if one were dividing 12,7 by 0,4 (commas being used instead of decimal points), the dividend and divisor would first be changed to 127 and 4, and then the division would proceed as above.
It is frequently stated that arithmetic right shifts are equivalent to division by a (positive, integral) power of the radix (e.g., a division by a power of 2 for binary numbers), and hence that division by a power of the radix can be optimized by implementing it as an arithmetic right shift. (A shifter is much simpler than a divider.