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Feature #487

ScalarProduct accepts MatrixRow?

Added by John Abbott about 10 years ago. Updated almost 5 years ago.

Status:
New
Priority:
Normal
Assignee:
-
Category:
CoCoA-4 function to be added
Target version:
CoCoA-5.?.?
Start date:
21 Mar 2014
Due date:
% Done:

0%

Estimated time:
Spent time:
0.50 h

Description

Yesterday I saw some old C4 code. In it the author had a call of the form ScalarProduct(M[I],L) where M is a matrix and L a list. Presumably it worked in C4; but it does not in C5 because ScalarProduct expects two lists.

An easy workaround is to write ScalarProduct(GetRow(M,I),L); not as compact or elegant as the C4 version, but its meaning is clear. I believe the function GetRow actually copies the entries, so there is a little wasted effort...

Should we extend ScalarProduct to accept MATRIXROW?

Related issues

Related to CoCoA-5 - Support #1031: ScalarProduct: exact defn and manual pageNew2017-03-17

Related to CoCoA-5 - Feature #1296: Matrixrow-functionsIn Progress2019-06-16

History

#1 Updated by John Abbott about 10 years ago

I'm rather undecided about this.

I suppose KISS would say not to widen the arg types accepted by ScalarProduct, at least no until we observe that it is a frequent paradigm.

One "irritating" aspect is that the obvious C5 implementation would probably work with MATRIXROW args. Actually, the only obstacle to it working is that len throws when given a MATRIXROW.

Opinions?

#2 Updated by Anna Maria Bigatti about 10 years ago

  • Target version set to CoCoA-5.1.0 Easter14

I like defining (mathematically) matrix multiplication by scalar products, so I'm in favour of adding it.
GetRow would makes copies, so can get quite costly in a loop.

I don't think it is trivial to implement, probably "not hard".

#3 Updated by John Abbott about 10 years ago

  • Target version changed from CoCoA-5.1.0 Easter14 to CoCoA-5.1.1 Seoul14

#4 Updated by Anna Maria Bigatti almost 10 years ago

  • Target version changed from CoCoA-5.1.1 Seoul14 to CoCoA-5.?.?

I think it is possible, but tedious work. Is it worth the effort?

#5 Updated by John Abbott about 7 years ago

  • Related to Support #1031: ScalarProduct: exact defn and manual page added

#6 Updated by Anna Maria Bigatti almost 5 years ago

#7 Updated by Anna Maria Bigatti almost 5 years ago

Anna Maria Bigatti wrote:

I like defining (mathematically) matrix multiplication by scalar products, so I'm in favour of adding it.
GetRow would makes copies, so can get quite costly in a loop.

I don't think it is trivial to implement, probably "not hard".

I changed my mind: MATRIXROW is a very dodgy type.

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