Comments on: Computer Algorithms: Adding Large Integers /2013/01/07/computer-algorithms-adding-large-integers/ on web development Fri, 26 Oct 2018 21:40:18 +0000 hourly 1 https://wordpress.org/?v=5.0.3 By: Scooby Doo /2013/01/07/computer-algorithms-adding-large-integers/comment-page-1/#comment-18585 Fri, 05 Apr 2013 09:00:37 +0000 /?p=3525#comment-18585 Well, I just can`t agree with you on that, Erik! The first time it took them 70 seconds because only one of them did the addition( let`s be honest, someone can take care of the carry overs in no time at all ) and the second time it took them half that time because they divided the task into 2 smaller problems which they could solve AT THE SAME TIME! So half the time for half the number… looks like simple math to me. The computer still has to add both halfs, so it would make no difference.

]]> By: Erik /2013/01/07/computer-algorithms-adding-large-integers/comment-page-1/#comment-18184 Thu, 17 Jan 2013 05:41:49 +0000 /?p=3525#comment-18184 I don’t fully agree with you. I illustrated this to two students of mine in the following way: A wrote two large numbers (in decimal) on the white board, one above the other, and told my two students to work as a team and add the numbers as fast as possible. They were allowed to discuss and come up with a strategy, but once ready, I said I would clock them. They decided on the following strategy: one would add single digit pairs and the other would take care of the carry overs. It took them 70 seconds to add the two numbers. Then I told them to try another strategy: Draw a vertical line through the middle of the two numbers, and then one adds the the part to the left and the other adds the part two the right. Although one of the students was puzzled for a moment, the other got it right away. He drew the line (took a second to think about where to draw it) and they proceeded as I had suggested. This time it took them 35 seconds. “What about carry over from the right part to the left part”, I asked them. “There is no carry over”, said the guy who had drawn the line. “You see, I drew the line here, so that there wouldn’t be any carry over.”

So the algorithm we all learn in school is not always the fastest one!

]]> By: dvh /2013/01/07/computer-algorithms-adding-large-integers/comment-page-1/#comment-18096 Tue, 08 Jan 2013 15:12:13 +0000 /?p=3525#comment-18096 well, probably correct when seen as a simplification.
however, taking a microscope and looking at the gate-level, you’ll see that there IS a difference between doing addition the ‘serial way’ we learned at school and using a carry-look-ahead-adder, which IS faster than the simple, straight forward algorithm.

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