Find Relative Error of A: 2.33

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Discussion Overview

The discussion revolves around calculating the relative error of a value \( A \) derived from a mathematical expression involving addition and subtraction. Participants explore the implications of their calculations and the definitions of relative error in the context of floating-point representation.

Discussion Character

  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant presents the calculation of \( A \) as \( A=(317+0.3)-(171.499+145.501) \) and claims to find the relative error as \( \frac{||A-fl(A)||}{||A||}=\frac{7}{5}=2.33 \).
  • Another participant confirms the values of \( A \) and \( fl(A) \) as \( A=0.3 \) and \( fl(A)=1 \), and recalculates the relative error, suggesting it should be \( \frac{|0.3 - 1|}{|0.3|} = \frac{0.7}{0.3} = 2.33 \).
  • A later reply corrects the initial claim of \( \frac{7}{5} \) to \( \frac{7}{3} \), indicating a potential misunderstanding in the calculation of relative error.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the correct calculation of relative error, with conflicting interpretations of the values and formulas used. No consensus is reached on the correct relative error value.

Contextual Notes

There are unresolved issues regarding the definitions and calculations of relative error, particularly in the context of floating-point arithmetic and the assumptions made about the values of \( A \) and \( fl(A) \).

evinda
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Hey! :rolleyes: I have also an other question :o
Suppose the base $\beta =10$ ,the precision $t=3$, $-L=U=10$ and $$A=(317+0.3)-(171.499+145.501)$$
I have to find the relative error for $A$.
We don't make rounding.For example,if we have the value $345.924$ it is equal to $0.345924*10^3$ and the corresponding floating number is $0.345*10^3$.
I found that it is equal to
$$\frac{||A-fl(A)||}{||A||}=\frac{7}{5}=2.33$$
Could you tell me if it is right?
 
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evinda said:
Hey! :rolleyes: I have also an other question :o
Suppose the base $\beta =10$ ,the precision $t=3$, $-L=U=10$ and $$A=(317+0.3)-(171.499+145.501)$$
I have to find the relative error for $A$.
We don't make rounding.For example,if we have the value $345.924$ it is equal to $0.345924*10^3$ and the corresponding floating number is $0.345*10^3$.
I found that it is equal to
$$\frac{||A-fl(A)||}{||A||}=\frac{7}{5}=2.33$$
Could you tell me if it is right?

I found that A=0.3 and fl(A)=1..
 
evinda said:
I found that A=0.3 and fl(A)=1..

Looks good! ;)... but doesn't that mean that:
$$\frac{||A-fl(A)||}{||A||} = \frac{|0.3 - 1|}{|0.3|} = \frac{0.7}{0.3} = 2.33$$

Oh wait! You also got $2.33$... while you shouldn't have. :eek: :rolleyes:
 
I like Serena said:
Looks good! ;)... but doesn't that mean that:
$$\frac{||A-fl(A)||}{||A||} = \frac{|0.3 - 1|}{|0.3|} = \frac{0.7}{0.3} = 2.33$$

Oh wait! You also got $2.33$... while you shouldn't have. :eek: :rolleyes:

I accidentally wrote $\frac{7}{5}$ :o I meant that it is equal to $\frac{7}{3}$..

Thank you very much! (Mmm)
 

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