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Error in 2-norm computation #222

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dpo opened this issue Jun 20, 2015 · 1 comment · Fixed by JuliaLang/julia#12571
Closed

Error in 2-norm computation #222

dpo opened this issue Jun 20, 2015 · 1 comment · Fixed by JuliaLang/julia#12571
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@dpo
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dpo commented Jun 20, 2015 

julia> VERSION
v"0.4.0-dev+5413"
julia> norm([2.4e-322,4.4e-323])
Inf

The same happens in 3.x.

Python:

>>> import numpy as np
>>> np.linalg.norm([2.4e-322,4.4e-323])
0.0

Matlab:

>> norm([2.4e-322,4.4e-323])
ans =
  2.4703e-322
nalimilan referenced this issue in JuliaLang/julia Jun 20, 2015
@nalimilan
Avoid overflow in generic_vecnorm()
9a9dc08 
No need to take the inverse too early. Fixes #11788.
nalimilan referenced this issue in JuliaLang/julia Jun 20, 2015
@nalimilan
Avoid overflow in generic_vecnorm()
f110415 
No need to take the inverse too early. Fixes #11788.
@nalimilan nalimilan mentioned this issue Jun 20, 2015
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nalimilan referenced this issue in JuliaLang/julia Jun 20, 2015
@nalimilan
Avoid overflow in generic_vecnorm()
0030786 
No need to take the inverse too early. Fixes #11788.
@nalimilan
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The issue is in the Julia generic implementation, Base.LinAlg.generic_vecnorm2, when taking the inverse of this:

julia> Base.LinAlg.vecnormInf([2.4e-322, 4.4e-323])
2.4e-322

julia> 1/Base.LinAlg.vecnormInf([2.4e-322, 4.4e-323])
Inf

I've made a PR to try to fix this: JuliaLang/julia#11789

@JeffBezanson JeffBezanson added bug Something isn't working linear algebra labels Jun 21, 2015
nalimilan referenced this issue in JuliaLang/julia Aug 11, 2015
@nalimilan @andreasnoack
Avoid overflow in generic_vecnorm()
2996f74 
No need to take the inverse too early. Fixes #11788.
andreasnoack referenced this issue in JuliaLang/julia Aug 11, 2015
@andreasnoack
Use division instead of multiplication with reciprocal when scaling
0b32a01 
elements in vecnorm methods. This fixes #11788.
@andreasnoack andreasnoack mentioned this issue Aug 11, 2015
Merged
andreasnoack referenced this issue in JuliaLang/julia Aug 11, 2015
@andreasnoack
Use division instead of multiplication with reciprocal when scaling
8ea075e 
elements in vecnorm methods. This fixes #11788.
andreasnoack referenced this issue in JuliaLang/julia Aug 11, 2015
@andreasnoack
Use division instead of multiplication with reciprocal when scaling
e29282d 
elements in vecnorm methods. This fixes #11788.
@KristofferC KristofferC transferred this issue from JuliaLang/julia Nov 26, 2024
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Avoid overflow in p norms JuliaLang/julia
Avoid overflow in generic_vecnorm() JuliaLang/julia
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@dpo @JeffBezanson @nalimilan