Opened 12 years ago
Closed 12 years ago
#282 closed bug (fixed)
Incorrect tensor product of rings in positive char
Reported by: | levandov | Owned by: | Oleksandr |
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Priority: | major | Milestone: | 3-1-2 and higher |
Component: | singular-kernel | Version: | 3-1-1 |
Keywords: | tensor product of rings | Cc: | Oleksandr |
Description
Daniel Andres (RWTH Aachen) has communicated the following: When tensoring a non-commutative ring over positive characteristic with an arbitrary ring with a parameter over the same characteristic, Singular 3-1-1 is stuck in an infinite loop.
This did not occur in version 3-1-0.
In version 3-1-1 it works for:
- commutative rings,
- rings without parameters over positive char,
- rings with parameters over char 0.
LIB "nctools.lib"; ring @W = 2,(x,Dx),dp; def W = Weyl(); setring W; W; // Weyl algebra in char p ring r = (2,a),y,dp; def B = W + r;
In his computation (3-1-1 official release) it resulted into an infinite loop. On my recent svn build it takes time, terminates, but delivers very incorrect non-comm relation.
setring B; B; // characteristic : 2 // 1 parameter : a // minpoly : 0 // number of vars : 3 // block 1 : ordering dp // : names x Dx // block 2 : ordering dp // : names y // block 3 : ordering C // noncommutative relations: // Dxx=-2147483647*x*Dx+-2147483647
I suppose the problem lies in the incorrect initalization of non-commutative part.
Change History (2)
comment:1 Changed 12 years ago by
Owner: | changed from hannes to Oleksandr |
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Status: | new → assigned |
comment:2 Changed 12 years ago by
Resolution: | → fixed |
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Status: | assigned → closed |
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Bug was
ALWAYS
present due to the following block in rSum / rSumInternal:since nSetMap can change something global, i.e. not usable after the next nSetMap call :(