TODAY'S HEADLINES  |   ARTICLE ARCHIVE  |   FORUMS  |   TIP BANK
 Specialized Dev Zones Research Center eBook Library .NET Java C++ Web Dev Architecture Database Security Open Source Enterprise Mobile Special Reports 10-Minute Solutions DevXtra Blogs Slideshow
 Sign up for e-mail newsletters from DevX

 Home » Tip Bank » C++
Language: C++
Expertise: Beginner
Jul 26, 2002

### WEBINAR:On-Demand

Building the Right Environment to Support AI, Machine Learning and Deep Learning

# A Fast Multiplication Method for Integer Numbers

The multiplication operation for integer numbers is implemented in the processor as repeated additions. The number of additions can be reduced by considering the representation in base 2 of the multiplier, as in this example:
``````
int i = 111;
//We need to compute int j = i * 15; but 15 = 1 + 2 + 4 + 8
= 2^0 + 2^1 +
2^2 + 2^3,
//so we can reduce the multiplication to some shift operations
and just 3 additions

int j = i + (I<<1) + (I<<2) + (I<<3);
``````

If you have multiplications in some lengthy iterative loops, using this trick can substantially increase CPU saving.
George Anescu

 Submit a Tip Browse "C++" Tips Browse All Tips
Comment and Contribute

(Maximum characters: 1200). You have 1200 characters left.

Thanks for your registration, follow us on our social networks to keep up-to-date