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Question a  Namir  02112005 Does anyone have an algorithm, written in some pseudocode, for one of the HP calculator SOLVER feature? I have read a few articles that were written by folks at HP who worked on the SOLVER feature. Yet I have not seen a pseudocode or even a source code in a popular language. I am planning to make a presentation at the next HHC (September of this year) conference. If you provide me with information I will give you credit at the conference. I have developed an algorithm that handles the following problems with the popular Newton method: 1)Low slope values near the root. 2)Oscillating guess values between asymptotic values/slopes of a function I appreciate your feedback. You can either post your reply here or email me at nshammasNULLSPAM@aolNULLSPAM.com (of course remove the NULLSPAM to get the actual email address). Many Thanks!
Namir
Re: Question about SOLVE  Thomas Okken  02112005 I have never seen any documentation about this outside of the HP Journal articles you mentioned. The article on the HP34C (December 1979) is interesting and gives some good insights, but no complete pseudocode. Many aspects of the algorithm (such as how to find x1 and x2 such that f(x1)*f(x2)<0, in case the initial guesses don't satisfy this condition and the initial secant iteration won't converge) are not discussed at all, which is a pity because there's clearly some very clever code at work there. I suppose one could try to ask HP nicely if they'd be willing to release that code, but somehow I doubt it  it seems like a valuable trade secret  and disassembling a calculator ROM and reverseengineering the pseudocode from the listing would be copyright infringement (unless you kept the result of that work to yourself, but where's the fun in that?). Alas! If I had that code I'd use it to make the Free42 solver better... But I guess we're on our own.
 Thomas
Re: Question about SOLVE  Namir  02122005 Thanks Tom for the info. The hybrid algorithm I developed does not detect and handle the case when the "guess" is in the area of a minimum value (in positive function values) or a maximum value (in negative function values), which I think HP's SOLVE does. The last time I treied my algorithm using f(x) = exp(x)  3*x^2 + 8, I gave it a guess of 4 and the algorithm found the only root AFTER MANY iterations. My personal standard test function is f(x) = exp(x)  3*x^2 which has three roots near ,45, 0.91, and 3.7.
Namir
Re: Question a  Bernardo Vargas  02222005 @Namir: You can look at the code of the SOLVE program included in the MATH1 module of the HP41 series.
