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In a computer with a full 32-bit by 32-bit multiplier, for example, one could choose B = 2 31 and store each digit as a separate 32-bit binary word. Then the sums x 1 + x 0 and y 1 + y 0 will not need an extra binary word for storing the carry-over digit (as in carry-save adder ), and the Karatsuba recursion can be applied until the numbers to ...
All the above multiplication algorithms can also be expanded to multiply polynomials. Alternatively the Kronecker substitution technique may be used to convert the problem of multiplying polynomials into a single binary multiplication. [31] Long multiplication methods can be generalised to allow the multiplication of algebraic formulae:
On platforms that support these instructions, a slightly modified version of the grid method is used. The differences are: Instead of operating on multiples of 10, they are operated on 32-bit integers. Instead of higher bits being multiplied by ten, they are multiplied by 0x100000000. This is usually done by either shifting to the left by 32 or ...
The instruction computes the 128-bit carry-less product of two 64-bit values. The destination is a 128-bit XMM register. The source may be another XMM register or memory. An immediate operand specifies which halves of the 128-bit operands are multiplied. Mnemonics specifying specific values of the immediate operand are also defined:
For example, to multiply 7 and 15 modulo 17 in Montgomery form, again with R = 100, compute the product of 3 and 4 to get 12 as above. The extended Euclidean algorithm implies that 8⋅100 − 47⋅17 = 1, so R′ = 8. Multiply 12 by 8 to get 96 and reduce modulo 17 to get 11. This is the Montgomery form of 3, as expected.
Here we consider operations over polynomials and n denotes their degree; for the coefficients we use a unit-cost model, ignoring the number of bits in a number. In practice this means that we assume them to be machine integers.
In mathematics and computer programming, exponentiating by squaring is a general method for fast computation of large positive integer powers of a number, or more generally of an element of a semigroup, like a polynomial or a square matrix. Some variants are commonly referred to as square-and-multiply algorithms or binary exponentiation.
Multiplying polynomials [ edit ] When using algebra tiles to multiply a monomial by a monomial , the student must first set up a rectangle where the length of the rectangle is the one monomial and then the width of the rectangle is the other monomial , similar to when one multiplies integers using algebra tiles.