236 views

Getting error General::munfl from NonlinearModelFit [duplicate]

I am trying to fit data to a sum of Gaussians. This data is found in a file called lpeff.txt. So I write the following code: ...
73 views

Numerical calculation Mathematica 11.2 / 11.3 / 12 [duplicate]

Please I do not understand why Mathematica 11.2 version evaluates numerically the value below Exp[-800]//N (* 3.667874584178*10^-348 *) while 11.3 and 12 ...
3k views

Incompatible Changes since Mathematica Version 7?

There is documentation of the incompatible changes made to Mathematica with each major release: Incompatible Changes since Mathematica Version 1 Unfortunately that documentation simply stopped ...
1k views

Speed up NDSolve compared to Python (calls to LSODA)

I migrated a numerical model code from Python to Mathematica and am surprised how much faster the Python version runs. Profiling of the Python version tells me that it is about 100 times faster (120 ...
456 views

Underflow error General::munfl from E^x instead of Exp[x]

In contrast to earlier versions, Mathematica 11.3 and 12.0 generate lots of underflow errors from my code, e.g. ...
184 views

Plotting with Precision

Suppose we plot Plot[Exp[x] Exp[-x], {x, 0, 1000}] This equals $1$, as expected, until around $x = 750$ where the curve drops sharply to $0$. Clearly this is due ...
235 views

How to check for underflow, and find a constant to correct it?

In a programme I'm running, at a certain point there's a multipplication of variables that gives underflow... For example $c=c_1\times c_2$. Is there anyway to check if that multiplication gives ...
116 views

Q: Problem - FullSimplify returns 0, FindRoot returns value & FindInstance requires system abend

The function at issue: ...
194 views

Plot3D discrepancy between MMA 10 and 11.3 - possible small numbers issue

I'm having some troubles with the following code I wrote in MMA 10 some time ago: ...
174 views

What Are the Changes in Working Precision in NIntegrate From Mathematica 10.2 to 11.3?

I have a simulation code I developed in Mathematica 10.2. I use Nintegrate to calculate some values. It works fine and each run takes about 170s. However When I run it in my university's computer (...
147 views

Can I force Mathematica to use machine precision? [duplicate]

Some built-in functions (like Exp) give an arbitrary precision result, even when the argument is a machine precision number. Example: ...
163 views

General:: Exp[-717.401] is too small to represent as a normalized machine number; precision may be lost

I am solving pde. For the post processing bvp, there is solution given in output which is the solution from mathematica version 10.0.1. Output from above in mathematica 10.0.1 is, But when the similar ...
46 views

Handling underflows

I am trying to implement an algorithm described for example in this paper, Section III, or referenced here, from where numerical parameters have been taken. I added the snippet I use to compute the ...
43 views

Set Underflow precision in Mathematica 12 same as version 11.x [duplicate]

It seems like Mathematica version 12 sets arbitrary underflow precision depending on the function, but I would like the underflow precision to be same as what was for previous version of Mathematica ...