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Increase the accuracy of "exp" and "exp2" #32

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PaulRBerg opened this issue May 18, 2021 · 2 comments
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Increase the accuracy of "exp" and "exp2" #32

PaulRBerg opened this issue May 18, 2021 · 2 comments

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@PaulRBerg
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Say you want to calculate e^88.722839111672999627. According to WolframAlpha, this is the correct answer:

340282366920938470811530194312354461908

But according to PRBMath, this is the answer:

340282366920938463220434743172917753977

I truncated the decimals in the Wolfram answer so that the numbers have the same precision.

The absolute delta between the two answers is a whopping 7591095451139436707931, a number with 21 digits!
@PaulRBerg
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Question: does adding 64 more magic factors in the "exp2" function increase the accuracy?

PaulRBerg added a commit that referenced this issue Jun 12, 2021
@PaulRBerg
perf: increase the accuracy of exp and exp2
6d28ff2 
chore: close issue #32
@PaulRBerg
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Question: does adding 64 more magic factors in the "exp2" function increase the accuracy?

Nope, that didn't cut it. What I ended up doing was change the internal representation used in PRBMath.exp2 from 128.128-bit to 192.64-bit.

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