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ptc-45285571-Visitor
1-Visitor
April 13, 2012
Question

Insufficient accurancy in my calculation!?

  • April 13, 2012
  • 1 reply
  • 1882 views

Hallo everybody!

I am having again troubles with my calculation.

I am getting closer to the finish line but today a have been faced unexpected problems and I can´t find the error.

I am calculating a 2 force progress which are periodic with 2*pi.

But they are phase shifted with the period "pi".

First it seems that the calculation works fine, but with the calculation of a small difference in the amplitude can be found.

This difference gets bigger and bigger with calculation process (you can see it on the diagrams).

I am searching for hours, but I can´t find a solution, please can somebody have a short look on my file?

Thank you very much in advance.

1 reply

M
MikeArmstrong1-Visitor
1-Visitor
April 13, 2012

Have you tried reducing TOL and CTOL under settings?

Mike

M
MikeArmstrong1-Visitor
1-Visitor
April 13, 2012

From Mathcad 11 help:

CTOL (Default = .001)

This controls how closely a constraint in a solve block must be met for a solution to be acceptable. A solve block controlled by CTOL consists of the word Given, one or more constraints to be met, and an optimizing function: minimize, maximize, find, or minerr. In order for the function to return a solution, the constraints in the solve block must be satisfied. For example, a constraint such as x<2 needs to be satisfied before a solution is returned. If CTOL=.001, this constraint is satisfied if x<2.001.

Change the value of CTOL to control the precision of the solution. The larger the value of CTOL, the less precise the solution may be. For smaller values of CTOL, a more precise solution is found, but the time needed to find a solution may increase.

TOL (Default = 0.001)

This controls the precision to which integrals and derivatives are evaluated. It also controls how long iteration in solve blocks and in the root function will go on for.

Setting TOL low

When you make TOL very low, all results are computed with much greater precision. Depending on the numerical properties of the expression this may increase computation time.

You may also see a did not find solution error message when the numerical properties of the expression are such that a solution asymptotically approaches a number that exceeds the acceptance threshold set by TOL.

Setting TOL high

High values of TOL will decrease computation time at the expense of precision.

P
ptc-45285571-VisitorAuthor
1-Visitor
April 15, 2012

Thank you for your reply!

But i made an type error which was very hard to find.

Now everything works fine!

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