Characteristic polynomial of symbolic matrix of size 7

ScreenName
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tmonteil
27483 ●32 ●205 ●519 http://wiki.sagemath.o...

There is a problem when computing the characteristic polynomial of a matrix of size greater than 7 containing a large number of symbolic variables.

a = SR.var('a', 100)
M = identity_matrix(SR, 7)
for i in range(7):
  for j in range(7):
    M[i,j] = a[i*7+j]
print(M.charpoly().degree()) # prints 5

The value it should print is 7. Over $\mathbb{Z}[a_0,a_1,\dots]$ , the result is correct.

I use Sage 8.3 (Release Date: 2018-08-03), installed from the official repository of Archlinux. The bug is present both in command line and with sage file.sage (if I copy and paste the code above).

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answered 6 years ago

arojas
241 ●5 ●8

Hi, This should be fixed now with pynac 0.7.22-5

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Thanks for the clarification !

tmonteil ( 6 years ago )

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answered 6 years ago

tmonteil
27483 ●32 ●205 ●519 http://wiki.sagemath.o...

updated 6 years ago

It works for me (Sage 8.4.beta7 complied on Debian stretch 64bit, run from the command line).

Could you please give us some informations so that someone can try to reproduce your problem:

which version of Sage did you use ?
which OS ?
did you install Sage from the binaries, and which ones ?
did you compile Sage yourself ?
which notebook did you use (Sage notebook or jupyter notebook) ?
did you use the command line ?
which commands did you type precisely to get the error ?
which error message did you get ?
... ?

EDIT thanks for reporting, it seems to be an issue with Archlinux port, since it works well on Sage Cell which also ships 8.3:

http://sagecell.sagemath.org/?z=eJxlz...

Second EDIT: this is now trac ticket 26427, i will contact Archlinux devs about that issue.

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I added information in the original post. I tried to install the 8.4 beta7 version but it failed.

ScreenName ( 6 years ago )

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