9
votes
Trace shows Linux has worse error than Windows in 1/(-1.)^1.2
This made me curious.
I work under macos on Apple Silicon. I get these results:
...
- 100k
7
votes
Accepted
How to use Slater Type Orbitals as a basis functions in matrix method correctly?
Your orbitals are not orthogonal to each other: here I've normalized them with an explicit formula (using FindSequenceFunction to discover it):
...
- 41k
6
votes
Accepted
How can I solve a three-dimensional Gross-Pitaevskii equation?
After proper normalization we have
...
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5
votes
Solving PDE with Dirichlet, Neumann and Boundary conditions
4 issues here, 2 are simple mistakes, 2 are not.
Though it happens not to cause problem in this case, your understanding for syntax of Piecewise is wrong, please ...
- 59.4k
4
votes
Accepted
4
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Why two the same integrals give different values?
Evaluating high-order polynomials is numerically unstable.
Example: exact evaluation followed by numericalization is stable,
Psi[7, 87] // N
(* -0.0271578 *)
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4
votes
Accepted
Trace shows Linux has worse error than Windows in 1/(-1.)^1.2
I'm not sure I understand the problem, despite attempts get clarification.
So far I'm not sure there is much more to this than to the following, this-is-school-math, behavior:
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3
votes
Accepted
3
votes
Solving PDE with Dirichlet, Neumann and Boundary conditions
modified
Thanks to @xzczd for the helpful discussion
Here my simplified version without ghost layer and mapping:
The ...
- 42.9k
3
votes
NDSolve with parametric endpoint
Integrating toward b[eta] = y'[eta] = 0 is challenging, because b[eta] occurs in the denominator of the first ODE. So, it ...
- 59.7k
3
votes
3
votes
Calculating the angle between vectors returns small complex number instead of zero
First note, the expression:
Transpose[{{10}, {12}, {4}}] . {{2.5}, {3}, {1}}
does not make sense. You are trying to mimic column and row vectors, but MMA does not ...
- 37.4k
3
votes
How to numerically solve a differential equation which has integration in it?
Some progress can be made as follows. First, rescale X by 10^7 to avoid large values of X (...
- 59.7k
2
votes
2
votes
Complex result for real vectors in VectorAngle
This is to note that at some point, this bug in VectorAngle has been fixed in or before V13.2:
...
- 226k
2
votes
Calculating the angle between vectors returns small complex number instead of zero
The numerical problems are two-fold and are independent of syntax and the OP's use of column matrices as vectors. The most serious problem is that round-off error leads to a range of
$$ -1-\delta \le {...
- 226k
2
votes
Accepted
Improving quality of plot with bad numeric performance
Don't use machine precision. Specify a WorkingPrecision to use arbitrary-precision.
...
- 139k
2
votes
Can Print no longer access certain values during evaluation?
It's not Print but FindRoot that has changed its behavior. FindRoot now evaluates its ...
- 226k
2
votes
CPU time in iteration process
How I set the CPU time or where I can check the CPU time for method
One way is to use TimeUsed[] and at the end subtract the times. Something like this
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- 127k
1
vote
Calculating the angle between vectors returns small complex number instead of zero
This problem does not occur when normalizing the vectors with Normalize:
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- 41k
1
vote
Calculating the angle between vectors returns small complex number instead of zero
This is not an answer, but too big for a comment. What you found is very annoying, and I can provide no solution.
But maybe the following code is of some help.
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- 1,833
1
vote
How to numerically solve a differential equation which has integration in it?
Perhaps StreamPlothelps to understand the problem little bit better
...
- 42.9k
1
vote
How to numerically solve a differential equation which has integration in it?
Not an answer, perhaps a starting point...
You could try to find an iterative solution (Picard iteration) using NestList starting with ...
- 42.9k
Only top scored, non community-wiki answers of a minimum length are eligible