## upwind scheme in Mathematica?

Mathematica

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• 1. Mathematica v6: Slower in the following fields
I installed v6, but had to return to 5.2 since - for some works I was doing - the new version has become unacceptably slow. Now I changed my mind and I keep both versions on, depending on what I have to do. I'd like to start this thread to see people post their observations about what has become slower in v6 - and of course what is faster too! e.g. some posts ago I saw somebody having problems with eigenvalues calculations. My problems, just to start, relate to graphics. Dealing with large images with ListContourPlot, for example, is really slower (had to kill the calculation). And ListDensityPlot is barely acceptable. So... please, add your experience here! Alessandro Magni
• 2. Number of Differing Digits & Another Problem (want to see different ways it can be done)
I just purchased a copy of Mathematica and I've been learning it for about a week now. You can expect that I will be posting a lot of questions. One thing I've noticed is that there are so many different ways to do the same thing! Here is a function I came up with that calculates how many binary digits two numbers differ in: BitDifferences[a_, b_, n_] := Count[Equal @@@ Thread[{IntegerDigits[a, 2, n], IntegerDigits[b, 2, n]}], True] For example 5 = 101 differs from 6 = 111 by one digit (the middle digit). I want to see how you would do it so I can broaden my Mathematica perspective. Thanks.
• 3. Mathstatica vs. built in symbolic statistics in Version 6
I have yet to use either the built in symbolic statistics in version 6, or Mathstatica. But, I hope to start using one of them soon. Is there anybody out there with experience in both packages that would care to comment on their general breadth and usefulness? Thanks in advance for any feedback. Cameron in Seattle
• 4. [Mathematica 6] Sudden shutdown of Mathematica. No error messages, no traces, no warning. Mathematica just disappears from desktop
I've noticed this now more than one time. I would say this has happened to me about 5-6 times already since I started using Mathematica 6 which is about 2 weeks now. This is what happens: I'll be working on an open notebook, and do something, for example, just now, I went to do SAVE AS to save the notebook. Mathematica would just disappear in split second. No errors, nothing. I look and it is just gone. All windows gone. No traces. I have to restart Mathematica. And I just lost all my work for the last 30 minutes. Strange thing is now when I open the document since I last saved it, it shows a help document from Mathematica document center. As if I was working on it instead of my own notebook. I remember having that help page open and I might have touched it somehow. But my notebook itself which I was working in is all gone. I'll try to see if there are logfiles somewhere which might show something. But this is really very very strange. Should I be looking somewhere? I looked at event viewer in XP, and do not see anything. Has anyone seen this? I am using Mathematica 6 student version on Windows XP SP2 home edition. thanks, Nasser
• 5. MinimizeProblem
On 5/19/07 at 4:48 AM, XXXX@XXXXX.COM wrote: >Why do I get? >In[4]:= >Minimize[(x^4-6 x^2+1)^2,{x}] >Out[4]= >{1,{x->0}} =46WIW, version 6 returns In[4]:= Simplify[Minimize[(x^4 - 6*x^2 + 1)^2, {x}]] Out[4]= {0, {x -> -1 - Sqrt[2]}}

### upwind scheme in Mathematica?

```hi all,

I am trying to solve convection-diffusion-reactions(in time and one
space coordinate) equations with NDSolve. Most of the time I am not
getting solution to my problem as solver fails to converge. I guess
the problem is very stiff and convection dominated. When I use upwind
difference scheme in fortran, I get the solution easily. How can use
upwind in NDSolve?
What is the method mathematica uses to solve pdes?

```

### Re: upwind scheme in Mathematica?

```
din NDSolve?

I am still looking of answer!

```

### Re: upwind scheme in Mathematica?

```

in=

Mathematica uses the method of lines to solve pdes numerically. To
the search box in the help system. (I don't know anything about upwind
methods.)

--Mark

```