Author: Robert Hyatt
Date: 08:44:30 10/03/01
Go up one level in this thread
On October 03, 2001 at 10:51:13, Miguel A. Ballicora wrote: > >There is between two separate searches through the hashtable, killers etc. >That is how "synergy" lowers the time in iterative deepening. > Ok.. You do a 5 ply iteration on one processor, and a 6 ply iteration on the other, in parallel, and show me the "synergy". Notice that your example is _exactly_ my point. "SERIAL". The 5 ply search _must_ be done first. It then orders the 6 ply search more efficiently. If you do them in parallel, you don't get this synergy. And actually, "synergy" is the wrong term here, because iterative deepening is _also_ a purely sequential algorithm. > >Yes, really. On other planets too. I am not going to discuss more on this >example because we are wasting time, yours and mine. It supposed to illustrate >an aspect of synergistic effects and nothing more. There many examples of this >in science. I understand you might not believe what I tell you, so please >believe any textbook that deals with friction and mechanics. Those are typical >examples. I have one right here. Which part would you like to discuss here? It is _always_ easier to drag than to lift and carry. Perhaps in "dragging" you have to provide a lifting force to overcome part of the friction. > >Faster solution does not involve expending more energy. Do not confuse >kinetics and thermodynamics. In fact, life is finding faster ways >to do things that might not look the most favorable (energetically). > That is _my_ point. But in your example, it _does_ involve expending more energy. One man can drag 10 200lb blocks N feet in M units of time. Two men can do that in M/2 units of time. If both drag a block together, they will expend more energy than if each drags one. Because the acceleration is not free and they have to move _twice_ as fast. And that means more "work" is being done. A computer can't do "more work". So the example simply doesn't apply. >You did not like Bruce's example? This one does not involve scientific >knowledge: >Team A: One person , 1 cart, 100 boxes too heavy to lift by only one person. >Team B: Two persons, 1 cart, same 100 boxes. >Task = move them 100 yards. > >Team B will take <50% of the time that it will take for Team A. Lifting >once onto a cart is easier than pushing. I use an inclined plane to slide the boxes onto the cart. Remember, if you expend _one_ more calorie of energy with your two guys, than I do by myself, the experiment is void. Because a parallel computer can _not_ execute more than 2x the instructions of a single computer, assuming a dual-processor box. > >>>Perfect to explain synergy. >> >>E=MV^2 doesn't explain synergy. It explains why it would be harder to move >>the thing twice as fast. It would take more energy than it would to move it >>at half the speed, just for the acceleration part... > >In a vacuum when there is not friction. We _both_ have to overcome friction. One of us has to expend the necessary energy to hold 200 pounds off the ground for the whole trip. The other doesn't. The unit of energy expenditure for the one person team must be exactly 1/2 or more of the energy expended by the two person team. Otherwise, the experiment has nothing to do with parallel search and super-linear speedup. It simply does _not_ exist in computing.
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