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cadjunkie

Member Since 28 Feb 2013
Offline Last Active Yesterday, 05:40 PM

Posts I've Made

In Topic: Two research papers being published as an undergraduate

25 August 2015 - 12:19 PM


it's so painful to read his 4 liner here that i can't believe anyone would read a whole paper from him

 

Ditto.

 

I discovered, yet everyone has coded them they are so obvious, two design patterns

 

Wait...how can you "discover" something everyone has done?


In Topic: Programming scientific GUI's, data and gui layout?

25 August 2015 - 09:10 AM


10 million isn't that much, 10 million floats is around 80MB, you can store that 10 times in just 1GB.

 

It seems you might not be familiar with finite element models. It's more than 10 million floats. I'm sure it's double precision, and each node has 6 degrees of freedom. Plus, each node can be tied to multiple elements, so there's element data there along with different types of stress and strain data. It's not uncommon for the output files to be 150+ GB, depending on what information is output.


In Topic: Programming scientific GUI's, data and gui layout?

24 August 2015 - 12:04 PM


You should avoid to store original and derived data into the same object. Treat it like variables in a programming language: You have a variable with the original data, you apply an operator, and yield in a result that is stored in another variable.

 

Not questioning the soundness of this advice (because I do think it's sound), but would that really be feasible on large data sets? Postprocessing something like finite element result data with 1 million nodes is very standard and larger models with 10+ million nodes are common too. I can't imagine trying to have 2 copies of that data in memory. I would think the original data is stored to disk and only 1 copy is in memory and gets operated on. If need be, then it gets reloaded. But maybe I'm wrong though...it's happened once or twice tongue.png


In Topic: How would I solve this polynomial equation system?

18 August 2015 - 12:50 PM

So there are i,n,m triples for which it cannot be solved, but is there a determined way to find out x,y,z solutions for provided i,n,m, or provide empty solution set ?

 

 

The only thing I can think of is to solve for z in the 3rd equation in terms of x using the quadratic equation: \( z = \frac{-mx \pm \sqrt{(m^2-4)x^2+8}}{2} \) and then substitute that into the 2nd equation. Then, subtract that result from the 1st equation*, then solve for x. Then, you can solve for z, and then y. 

 

*EDIT: Even this way I couldn't eliminate all the y's from the equation. Maybe there's some trick there, but I can't see it.

 

If you're asking for a general analytical (not numerical) technique, I'm not sure what it would be.


In Topic: How would I solve this polynomial equation system?

13 August 2015 - 10:16 AM

I wouldn't say so. For example, the i,n,m of values 0,0.5,0.5 would have a solution of [0,sqrt(2),sqrt(2)]/[0,-sqrt(2),-sqrt(2)].

 

The solutions set is empty only at a rather small subset of i,n,m where sum of them three is very close to 3.0, and equal to 3.0, but I only gess so, it is possible that solution does not exist only for (i,n,m)=(1,1,1).

 

 

So let me see if I got this straight:

  • You've added scalars to account for a non-zero dot product in an attempt to say that your D, G, and F vectors aren't orthogonal.
  • Your system of equations is simplified from the distance equation where you've considered each plane formed by every pair of vectors. 
  • You want the Euclidean distance between the vectors in their respective plane to be sqrt(2).

The thing that bothers me is that x, y, and z are parametric with respect to D, G, and F, but there's no restriction on the directions of D, G, and F or enough restrictions on the values of x, y, and z, so we have way too many unknowns and not enough equations. Although you've basically restricted the dot products of the vectors to be between [0,1], I don't see how you can generate a solution set without either exhausting the possibilities or adding more constraints.


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