Questions tagged [machine-precision]
For questions on the use of machine-precision real numbers (also known as floats), the numbers that can be directly manipulated through the underlying numerical capabilities of your computer system.
229
questions
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Meaning of backtick in floating-point literal
If I compute, say, 1/3//N, Mathematica displays
0.333333
as the result.
When I copy that output to use elsewhere,
the paste ...
- 88.3k
0
votes
1
answer
2k
views
How to get more accurate orthonormal eigenvectors?
I have a matrix M with real entries in MachinePrecision. I compute its eigenvectors and construct matrix ...
- 38.8k
0
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0
answers
70
views
0
votes
2
answers
240
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The precision of the number
I have problem in Mathematica with unnecessary rounding which is caused by high precision.
For example I have value a = 2.052685846*10^-1865, when I make ...
- 270k
4
votes
2
answers
2k
views
Floating point addition not associative
Can anybody explain the following behavior?
x = 0.2 + (0.3 + 0.1);
y = (0.2 + 0.3) + 0.1;
x == y (* -> True *)
But actually the variables do not exactly ...
- 32.4k
2
votes
1
answer
2k
views
Plot periodic function from Dirac delta function [duplicate]
Sorry for my bad english.
I need to plot periodic function from dirac delta:
δT(t)=∑δ(t–n*T), where T - is a constant, and n=-20..20
And after them, plot new function fd=f(t)*δT(t) - discrete signal ...
- 68.3k
5
votes
1
answer
2k
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Error about limit MaxExtraPrecision
After my evaluations I have an error:
N::meprec: Internal precision limit $MaxExtraPrecision=50. reached while evaluating ...
...
- 787
2
votes
1
answer
526
views
How to use adaptive precision in matrix computations?
I wish to compute the pseudo inverse of rectangular (or square) matrices by the cubically method of Chebyshev given by $X_{k+1}=X_k(3I-AX_k(3I-AX_k))$ where $X_0=\frac{1}{\|A\|_F^2}A^*$. The procedure ...
- 22.9k
3
votes
1
answer
281
views
Why to do parentheses change the results of a calculation?
I'm getting results that are sensitive to where I place parentheses with respect to operations that are associative1 (and should thus be insensitive to such placement). For example, if I define2
<...
- 88.3k
2
votes
0
answers
568
views
how to calculate with just double floating point precision [duplicate]
I want to calculate with simple double floating point precision.
...
- 137k
0
votes
1
answer
272
views
How to improve the performance of this code
I have implemented a code in Mathematica 9 to simulate a scattering problem, and I got really disappointed about its performance when compared to Matlab. Since I am a newbie in Mathematica, would ...
- 5,340
2
votes
2
answers
177
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Long run time for older code that ran fast in older versions
The following code block is in Trott's Guidebook for Programming. The associated notebook says that this and a few other routines ran in a matter of seconds. I killed it after half an hour.
I am ...
- 84.6k
4
votes
1
answer
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CompiledFunction::cfse: "Compiled expression X should be a machine-size integer
I am trying to use a compiled function in order to save time...
LegrendeTransform = Compile[{y}, MaxValue[Sin[x] - x *y , x]]
Now I want to to evaluate and ...
CommunityBot
- 1
1
vote
1
answer
64
views
Function that puts zero after a certain decimal in every element of the matrix
We know that in Mathematica there is some default precision, which you can also change. This means, that after a certain decimal(fixed by the precision), the computer puts pseudo random numbers.
I am ...
- 58.7k
9
votes
3
answers
2k
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Very different results from evaluating same expression with different precisions
When I evalute the following expression,
...
CommunityBot
- 1
0
votes
1
answer
320
views
Finite precision - how to get rid of "near zeros" [duplicate]
I am performing a finite-precision operation on a matrix A which I know precisely; call the result B. The operation is taking ...
- 3,547
2
votes
1
answer
371
views
Why is arithmetic faster for inexact arithmetic?
I have been trying to compute eigenvalues of a rather sizable matrix A, about $500 \times 500$ (but sparse). I asked Mathematica to compute ...
- 68.3k
7
votes
4
answers
3k
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Mathematica Precision
How can I set the output precision of the following statement to 10 decimal places? I was looking through the documentation, and for some reason, all I could find was ...
- 2,294
1
vote
1
answer
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Adding precision for the calculation of a function
I have some function $f(x)$ I wish to evaluate, which is yielding divide-by-zero errors for sufficiently large inputs. How do I increase the precision with which this function is evaluated in order ...
- 14.6k
9
votes
2
answers
605
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Precision differences
I run this sum and get the symbolic answer below :
Sum[ (1/(k^2 - k) - 1/k^2), {k, 2, Infinity}]
$2 - \frac{\pi^2}{6}$
I look up the sequence on OEIS and ...
- 56.7k
2
votes
1
answer
857
views
How to Chop correctly?
I want to count degeneracies in a list called spectrum. The list contains numbers of double (~ 15digits) precision. So it makes no sense if the noise below this ...
- 19.7k
2
votes
2
answers
1k
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FindRoot errors
I'm trying to solve a system of two equations in two variables for some range of parameter values. I use ContourPlot to see where I should look for a solutions and ...
- 6,818
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votes
0
answers
2k
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Set Global Maximum Precision
I'm sure this has been asked before, but I've looked around and can't figure it out:
How do I set a global maximum precision for a notebook (or in general, globally)?
I have a large notebook in ...
- 625
4
votes
2
answers
3k
views
Precision of number not maintained when saved via Export
Assume that the output of my calculation is a and is a number such as:
a = 100.1252135246354847;
...
- 5,321
4
votes
1
answer
843
views
Could the PrecisionGoal for NDSolve be a negative number?
The help of Mathematica doesn't say so much about the PrecisionGoal for NDSolve, and I never considered much about it even after ...
CommunityBot
- 1
10
votes
3
answers
896
views
Mathematica Plot: Inconsistency when plotting large values
I am working with a function in Mathematica and I am getting some inconsistencies when I plot it. As I really need to understand were this comes from I would appreciate any help.
I am working with a ...
- 61.4k
5
votes
1
answer
2k
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Infinite expression 1/0. encountered - caused by precision?
Planck's law dependent on frequency rho is as follows:
B[T_, h_, rho_, k_, c_] := (2 h rho^3)/c^2 1/(Exp[h rho/(T k)] - 1)
As you can see, the denominator can ...
CommunityBot
- 1
20
votes
1
answer
2k
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Quadruple-precision (128 bit) arithmetic
Is it possible to force Mathematica to perform computations with hardware supported quadruple-precision? The following test suggest, that all of the computations with fixed precision, different than <...
- 96.8k
7
votes
1
answer
156
views
Using Differences on data: trouble with floats and doubles
Consider the following data set (after I have run FullForm), which is imported from a file (stored typically as 10.040):
...
- 88.3k