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multiplication is not checked by default for overflow #5054

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StefanKarpinski opened this issue Dec 7, 2013 · 3 comments
Closed

multiplication is not checked by default for overflow #5054

StefanKarpinski opened this issue Dec 7, 2013 · 3 comments
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bug Indicates an unexpected problem or unintended behavior
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0.4.x

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@StefanKarpinski
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julia> 128738872312*invmod(128738872312,9223372036854775783)
9223369465230597584

julia> ans < 9223372036854775783
true
@vtjnash vtjnash added this to the 0.4 milestone Apr 25, 2014
@skariel
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skariel commented Sep 20, 2014

You are overflowing the invmod return value, which is an Int64. The following works good:

BigInt(128738872312)*invmod(128738872312,9223372036854775783)

so, this is no bug I guess :)

@vtjnash
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vtjnash commented Aug 26, 2015 

julia> Base.checked_mul(128738872312, invmod(128738872312,9223372036854775783))
ERROR: OverflowError()
 in checked_mul at int.jl:514

@vtjnash vtjnash changed the title invmod: incorrect for large moduli multiplication is not checked by default for overflow Aug 26, 2015
@vtjnash
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vtjnash commented Aug 26, 2015

duplicate of #855

@vtjnash vtjnash closed this as completed Aug 26, 2015
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@StefanKarpinski @vtjnash @skariel