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Macaulay2 / M2

The primary source code repository for Macaulay2, a system for computing in commutative algebra, algebraic geometry and related fields.
https://macaulay2.com
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Order of entry multiplication for matrix multiplication #131

Open jimmathews opened 10 years ago

jimmathews commented 10 years ago

I'm not sure if there is a reason for this, but it appears that M2 multiplies the entries of matrices in the `opposite ring'. This is undetectable for commutative rings, but gives unexpected results in the skew-commutative case.

DanGrayson commented 10 years ago

That's true, and it's documented at http://www.math.uiuc.edu/Macaulay2/doc/Macaulay2-1.6.0.1-20131031-2/share/doc/Macaulay2/Macaulay2Doc/html/_right_spmodules_spor_spleft_spmodules_qu.html . (There should be more links to that page.)

I wish we had done it the right way.

mikestillman commented 10 years ago

I thought we did do it the right way?

On May 12, 2014, at 7:03 PM, "Daniel R. Grayson" notifications@github.com wrote:

That's true, and it's documented at http://www.math.uiuc.edu/Macaulay2/doc/Macaulay2-1.6.0.1-20131031-2/share/doc/Macaulay2/Macaulay2Doc/html/_right_spmodules_spor_spleft_spmodules_qu.html . (There should be more links to that page.)

I wish we had done it the right way.

— Reply to this email directly or view it on GitHub.

DanGrayson commented 10 years ago

By "right" here, I mean standard and customary, not mathematically consistent. For example, since we wanted the matrices to act on free modules on the left, we could have had the scalars act on free modules on the right, i.e., we could have decreed all R-modules to be right R-modules.

On Mon, May 12, 2014 at 6:34 PM, Mike Stillman notifications@github.comwrote:

I thought we did do it the right way?

On May 12, 2014, at 7:03 PM, "Daniel R. Grayson" < notifications@github.com> wrote:

That's true, and it's documented at http://www.math.uiuc.edu/Macaulay2/doc/Macaulay2-1.6.0.1-20131031-2/share/doc/Macaulay2/Macaulay2Doc/html/_right_spmodules_spor_spleft_spmodules_qu.html. (There should be more links to that page.)

I wish we had done it the right way.

— Reply to this email directly or view it on GitHub.

— Reply to this email directly or view it on GitHubhttps://github.com/Macaulay2/M2/issues/131#issuecomment-42901578 .