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.

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3
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1answer
79 views

Why does precision decrease after increasing PrecisionGoal and WorkingPrecision on this integral?

I am trying to calculate a messy double-integral to many digits of precision. As shown below, the precision seems to increase reliably as WorkingPrecision goes from ...
0
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1answer
80 views

How to improve working precision?

I'm trying to fit the array data as follow: NonlinearModelFit[ data, s*t^r + (A/(w*(Pi/2)^0.5))*Exp[-2*((t - u)/w)^2], {s, r, A, w, u}, t]; But when ...
1
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1answer
31 views

How to get the output for the following code involving differentiation and integration?

I need to evaluate the following Mathematica code to get a numerical value as my output. But during compilation I get the error message NumericalMath`FixedPrecisionEvaluate::precbd: Requested ...
0
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0answers
61 views

Understanding Working Precision - two example equations

I am trying to understand how WorkingPrecision works, and in general how very small/large numbers are to be handled. Let me preface I probably do not have ...
0
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0answers
20 views

Conflicting output provided by `N[…]`

I am trying to evaluate an expression : (-((I (k2 - k1) (-1 + E^(2 I (k2 - k1) \[Pi])))/(-1 + (k2 - k1)^2))) /. {k1 -> 2, k2 -> 7} This gives ...
0
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0answers
39 views

Dealing with General::munfl errors

Edit: So, while trying to figure out a minimal exmaple, I found out that my main problem was actually unrelated to this and it just happened to be that giant pile of warnings and error messages coming ...
5
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1answer
81 views

Equality for floats

Suppose I have two floats (e.g. {x,y} = RandomReal[{0,1},2]). Might there be a situation where all three comparisons evaluate to ...
1
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0answers
46 views

Numerical precision - simulating an unstable equilibrium

I was playing around with NDSolve and the following ODE s = NDSolve[{y''[x] == -Sin[y[x]], y[0] == \[Pi], y'[0] == 0 }, y, {x, 0, 120}] The equation and the ...
3
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1answer
90 views

DeleteCases with a case as float?

Might the DeleteCases have issues in matching when the list is of floats (machine precision numbers)? E.g. in this code it might fail to match correctly because ...
2
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0answers
40 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 ...
1
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0answers
49 views

FindRoot giving error in Mathematica version 12

I was using the same code in previous version of Mathematica but unfortunately I had to update Mathematica to version 12 because I upgraded MacOS to Catalina. Now when I run my code, I get this error ...
4
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0answers
121 views

How does Mathematica evaluate N[π, 30] == π?

I want to know how N[π, 30] == π works. The result is True. I wonder whether the exact number ...
1
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0answers
32 views

Changing machine precision notebook-wide leads to peculiarities

For a project of mine it is preferrable to set notebook precision globally. I have done so by using the answer in Global precision setting. The idea is to dynamically create a ...
9
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2answers
307 views

How to detect underflow/overflow (post 11.3)?

This old trick used to work before 11.3: SetSystemOptions["CheckMachineUnderflow" -> True] But no longer... so how can we explicitly check for this in v12+?? ...
0
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1answer
66 views

Allow Mathematica to solve the differential equations with larger than 16 digits parameters

Consider the system of differential equations ...
1
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1answer
60 views

why some parts of my curve are removed or wiped

When I try to draw the next code I get a curve with missing parts, as shown in the picture. I do not know if it is an precision problem in the Mathematica program or is some data not calculated. Or is ...
0
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1answer
62 views

Why this very simple problem turns to “Indeterminate”?

Why the following calculation gives Indeterminate value? ...
0
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1answer
55 views

Preventing Mathematica from considering small values to be equal to zero [duplicate]

In my calculations I have a variable (say z) which can be an argument of Log, say, z Log[z]. ...
0
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0answers
50 views

How to resolve underflow occurrences?

I am solving a second order differential equation described by odey below. For the asymptotics, I have the following code which will be used as initial conditions for NDSolve. ...
3
votes
1answer
84 views

Setting precision and machine underflow

As is well known, Mathematica changed how it handles numbers smaller than $MinMachineNumber in recent versions. I'm running Mathematica 12 on a Mac, and I cannot figure out why it's treating these ...
2
votes
1answer
170 views

Why would Evaluate[] in Plot give me warning about precision?

I have a code:- Plot[Evaluate@PDF[NormalDistribution[1.6, 0.2], x], {x, -6, 6}] And then I got the warning: ...
1
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1answer
86 views

Number definition and approximation

I run these lines: a = 0.833 SetPrecision[a, 20] and this is the output: 0.833 0.83299999999999996270 I expected to ...
2
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2answers
179 views

Why is Mathematica's default precision only 16 digits? [closed]

I was performing some basic computations when I noticed that NumberForm[N[Zeta[3]], {100, 100}] yields ...
5
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2answers
379 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. ...
2
votes
1answer
112 views

Correct syntax for working precision in functions version 12

I just recently updated from version 11.2 -> 12...there apparently are quite a few changes since 11.2. $\unicode{952}\unicode{960}$ One being how version >11.3 deal with numbers that approach zero. ...
1
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3answers
85 views

When should one write integer numbers with a decimal?

I often see different solutions where users have taken advantage of how Mathematica handles numbers differently. I.e. when is it appropriate to use a decimal point in a calculation? Can someone ...
1
vote
1answer
79 views

Drawing from InverseWishartMatrixDistribution. A machine precision error?

I'm drawing from the Inverse-Wishart Distribution, but I got the following error message: ...
1
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1answer
180 views

How can I suppress the warning “precision may be lost”?

When I import data from a .dat file, V11.3 emits the message: is too small to represent as a normalized machine number; precision may be lost. How can I close the ...
4
votes
1answer
221 views

Inexact numbers as keys in Association?

Can someone explain me how Mathematica's Associations behave with inexact numbers as keys: <| 0.22499999999999964` -> a |> [0.22499999999999965`] and <...
2
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1answer
93 views

Efficient Round edition with different rounding direction

As pointed out in this post, Mathematica has a special version of Round that Round rounds numbers of the form x.5 toward the nearest even integer. A comment by ...
2
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1answer
126 views

How to prevent Mathematica from giving inexact answers

Upon doing a simple subtraction 13.725 - 13.5 both Mathematica 11.3 and 12.0 beta version are giving me 0.22499999999999964 ...
3
votes
1answer
64 views

Forcing divisions to be a machine-precision floating point divisions instead of multiplication by inverse

I want to imitate machine-precision, de facto IEEE division on Mathematica. On my quick trials I find this surprisingly hard to accomplish, since Mma rewrites a / b ...
0
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1answer
65 views

ContourPlot showing breaks in contours

I'm trying find graphically the solutions of the intersection of the following functions. ...
2
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2answers
237 views

Why is 0 vs 0.0 causing a precision problem?

I wasn't sure what to title this Question. I tried calculating different forms of a continued fraction, and I found that I get a correct result when I set d to 0 but a wrong result (in the final two ...
5
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0answers
67 views

Small positive machine number calculation in Mathematica 11.3

In Mathematica version < 11.3, any positive Machine‐Precision Numbers exceeding the range [$MinMachineNumber,$MaxMachineNumber...
6
votes
1answer
107 views

Extracting binary digits of machine precision numbers

Currently, I am developing an octree data structure. And I need it to be fast. To this end, I would like to have a fast way to extract the $m$ binary digits "after the dot" of each entry in a matrix ...
1
vote
2answers
468 views

Truncate a number in mathematica

I want to truncate a simple number to n decimal digits. For example, 2/3. I used f[x_, n_] := N[IntegerPart[x 10^n]/10^n] but I get ...
0
votes
1answer
56 views

How to get the correct result in a simple operation in Mathematica

I have the following values for x[[i]], y[[i]] and A[[i,j]]: ...
2
votes
2answers
143 views

What's the smallest positive real allowed in mathematica?

This question may be a bit strange, but in this question, one of the answers suggests substituting some negatives values in a matrix by the smallest positive real number allowed. So, I was wondering ...
0
votes
1answer
48 views

Simple division with high precision in Mathematica [closed]

I want to do a simple division i.e. 0.70524/0.51824 . What I want is to find the result of the roundation of this division for precision from 1 to 19 decimal digits....
3
votes
1answer
83 views

Numerical precision problem

I have this simple code: ep = 1 - 80000000000 (-(199999/200000) + 1/E^(1/200000)) ep // N -8.27404*10^-8 ...
0
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0answers
147 views

Plot a function with very small values, close to zero

I want to plot a function with very small values, close to zero, but even though the limit is -3/2 as x->0, I can't get any ...
2
votes
1answer
90 views

Copy-paste with annoying trailing 0s

When one copies an output containing machine-precision numbers to a input, many trailing 0s appears. For example : Evaluate the following expression : ...
0
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2answers
74 views

equal expressions give different numerical result

I have two expressions, and they are really equal: ...
2
votes
1answer
71 views

Working Precision warnings for ParametricPlot

I wish to plot a series of parametric curves for the following function called poly that has five parameters (Γ, ...
1
vote
1answer
41 views

How to choose elements of a matrix with internally generated variables and rank them with real coefficients

I have a Code (a long one), part of it is below. The following piece basically multiplies an adjacency matrix with a vector of equilibrium values. Then tries to pick non-zero elements to be used in ...
14
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4answers
449 views

Terrible accuracy of DawsonF

DawsonF[30.] returns 0. The correct value is 0.016676... At least it prints a warning message, ...
5
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2answers
382 views

Why does N not upgrade precision? [duplicate]

Precision[N[1.0, 20]] Precision[N[1, 20]] MachinePrecision 20. It would be so much more intuitive and less error prone, if <...
9
votes
1answer
177 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: ...
4
votes
1answer
100 views

Machine Epsilon is not equal to $MachineEpsilon [duplicate]

I try to wrap my head around machine precision calculations in Mathematica (11.2, Linux). I do not understand the following behavior: ...