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Java Forum / General / April 2006calculating the a bigdecimal to the power of double
I have a bigdecimal and a double value,say Bigdecimal bd = 599999.45; double d= 5.9; i want to do 599999.45^5.9 Note:I dont want to convert bigdecimal to double thanks in advance. > I have a bigdecimal and a double value,say > [quoted text clipped - 4 lines] > > Note:I dont want to convert bigdecimal to double Raising a decimal to the power of 5.9 isn't going to result in a number expressible as a decimal. If you want more accuracy than provided by double, I guess you could use a series expansion. Tom Hawtin  SignatureUnemployed English Java programmer http://jroller.com/page/tackline/ I don't think you can xor floating points just integers. >I don't think you can xor floating points just integers. He means ^ to represent power. SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. There must've been some invisible thing on there. ;) hehe Ah, the title! sh.t, I never look there. ;) manzur wrote On 04/19/06 12:15,: > I have a bigdecimal and a double value,say > [quoted text clipped - 4 lines] > > Note:I dont want to convert bigdecimal to double Suggestion #1: Convert it to double anyhow, despite your dislike of the approach. Suggestion #2: Re-examine what you're trying to do. Is it really a good idea to use a BigDecimal here? Suggestion #3: Get out your Numerical Methods books and start writing implementations for transcendental functions of BigDecimal values, using add() and multiply() and the other methods of BigDecimal to perform the underlying arithmetic. (Warning: This will probably not be a project, but a PROJECT ...) SignatureEric.Sosman@sun.com >Bigdecimal bd = 599999.45; >double d= 5.9; That won't compile for two reasons. 1. you spelled BigDecimal incorrectly 2. BigDecimal is not a primitive. You need to use a method or constructor to create a BigDecimal value. SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. > I have a bigdecimal and a double value,say > [quoted text clipped - 6 lines] > > thanks in advance. As already said, non-integer powers in BigDecimal would be a significant project. Maybe there is a less drastic solution to your problem. Could you explain why you don't want to do the power calculation in double? That may give someone ideas for alternatives. Patricia > As already said, non-integer powers in BigDecimal would be a significant > project. Indeed. I implemented it years ago for a COBOL compiler and it took several weeks. Even finding the constants for the polynomials is a project in itself: for example, they are in a book which is out of print and selling for large enough prices that I don't want to name it ;-) or you can compute them yourself but then you have just started several *more* projects. > > I have a bigdecimal and a double value,say > > [quoted text clipped - 15 lines] > > Patricia iam writing code for some banking applications which demand accuracy in money values.For money values iam using Bigdecimal. If i convert my bigdecimal to double i fear of inaccuracy(In cases where i deal with huge values greater than double) >>>I have a bigdecimal and a double value,say >>> [quoted text clipped - 21 lines] > bigdecimal to double i fear of inaccuracy(In cases where i deal with > huge values greater than double) You won't be dealing with values greater than double, because the maximum double is bigger than 10^308. That is more than the probable number of atoms in the observable universe. However, it is entirely possible that you could get a wrong answer for the least significant digit on large sums of money. Double is just about precise enough to get the cents digit right on the US national debt in dollars. If that is good enough, one solution might be to use double for the exponentiation, but immediately convert back to BigDecimal. That would avoid accumulating rounding errors during routine addition and subtraction. I'm a bit surprised by the use of exponentiation in this precise an environment. For example, I would have expected compound interest to be done a compounding period at a time, with the interest for each period rounded according to fixed rules, then added to the balance. Patricia > I'm a bit surprised by the use of exponentiation in this precise an > environment. For example, I would have expected compound interest to be > done a compounding period at a time, with the interest for each period > rounded according to fixed rules, then added to the balance. Another possibility is that "perfect" precision is not required for /this particular/ calculation. For instance in the UK any offer of a loan must be accompanied by (besides the exact statement of interest, etc) an indicator figure which is supposed to make it easier for people to compare offers with different conditions. I forget the thing's name, and the rules for computing it are complicated, but the point is that floating-point accuracy is entirely adequate, even though it's a financial calculation. -- chris > iam writing code for some banking applications which demand accuracy >in money >values.For money values iam using Bigdecimal. If i convert my >bigdecimal to double i fear of inaccuracy(In cases where i deal with >huge values greater than double) Hmm. What you might do is get a good initial approximation with Math.pow on double. Then use a Newton-Raphson to home in on a very accurate value. SignatureCanadian Mind Products, Roedy Green. http://mindprod.com Java custom programming, consulting and coaching. Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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