Multiplication algorithm: Difference between revisions

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Linear time multiplication: This section is very confusing. Knuth is describing the Schönhage–Strassen algorithm (or one of their algorithms); a discussion on machine models can be useful, and can be based on the recent preprint of Fürer.
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== Shift and add ==
 
Historically, computers used a "shift and add" algorithm forto multiplyingmultiply small integers. Both base 2 [[#Long multiplication|long multiplication]] and base 2 [[peasant multiplication]] reduce to this same algorithm.
In base 2, multiplying by the single digit of the multiplier reduces to a simple series of [[logical AND]] operations. Each partial product is added to a running sum as soon as each partial product is computed. Most currently available microprocessors implement this or other similar algorithms (such as [[Booth encoding]]) for various integer and floating-point sizes in [[hardware multiplier]]s or in [[microcode]].