Why carry lookahead adder (CLA) is used instead of Ladner-Fischer adder (LFA)?

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mhytr

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I read one paper today,and Ladner-Fischer adder(LFA) is said to be the fast adder in this paper.But it seems that carry lookahead adder(CLA) is more frequently used for high speed application.And in this paper the data presents that LFA is faster than CLA,and also cost smaller gates than CLA.
If LFA is better than CLA both in speed and space,then why CLA is much more frequently used(i am not so sure now) ,at least,i can find the introductioo of CLA on different textbooks but i have never seen any about LFA.
thanks!
 

ladner fischer adder

Reason may be...
1. People are not aware this..
2. LFA is patented and not yet expired and people dont want to spend mony on roalty!
 

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