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*Subject*: Re: co2calc.f and ta_iter_1.f*From*: maier-reimer@dkrz.de ("E.Maier-Reimer")*Date*: Mon, 19 Jul 1999 17:20:34 +0200 (MET DST)

Jim, that is not true It depends, of course on the amount of chemical changes since the previous computation. two or three iterations are suffient for roundoff error on a 64-bit machine. Practically, one iteration would be sufficient, indeed. some reminders for optimization: (trivial) call of subroutines should be done with arrays not with single variables for vectorization the choice of phhi and phlo is rather irrelevant once you are at 10**(-8) the iteration will hardly touch the bounds. For crazy starting values it is sufficient to ensure that htotal does not come below , say, 10 % of the previous guess It may be more efficient to do 3 iterations for the whole array than than to perform sophisticated checking for avoiding redundant algebra I made the experience that even advenced programmers are not aware of the fact that sqrt, log, exp sin cos are extremely time consuming. a**b is even worse the chemical constants should not have higher temporal resolution then other fields. I strongly recommend to provide monthly fields and interpolate for the actual timestep. Ernst

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