From: merch-redmine@jeremyevans.net
To: ruby-core@ruby-lang.org
Subject: [ruby-core:94513] [Ruby master Bug#12356] Vector covector incorrect multiplication with another vector.
Date: Fri, 23 Aug 2019 22:35:50 +0000 (UTC) [thread overview]
Message-ID: <redmine.journal-80949.20190823223549.dc9aab4cb2feb60e@ruby-lang.org> (raw)
In-Reply-To: redmine.issue-12356.20160506235154@ruby-lang.org
Issue #12356 has been updated by jeremyevans0 (Jeremy Evans).
Assignee set to marcandre (Marc-Andre Lafortune)
Status changed from Open to Assigned
I don't think this is a bug, but I'll let marcandre make the determination. `Vector` can't be multipled with `Vector`, you get an error. You can multiple a `Vector` by a `Matrix` and vice-versa by design, and `Vector#covector` returns a `Matrix`. You can multiple a `Matrix` by a `Matrix` only if the column_count of the receiver is the row count of the argument.
Whether `Vector` is good design or bad design I'm not going to speculate on. However, you could consider using NMatrix (https://rubygems.org/gems/nmatrix), as that represents vectors as matrices.
----------------------------------------
Bug #12356: Vector covector incorrect multiplication with another vector.
https://bugs.ruby-lang.org/issues/12356#change-80949
* Author: edmorte (Rafael Silva)
* Status: Assigned
* Priority: Normal
* Assignee: marcandre (Marc-Andre Lafortune)
* Target version:
* ruby -v: ruby 2.2.4p230 (2015-12-16 revision 53155) [x86_64-linux]
* Backport: 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN
----------------------------------------
Version 2.2.4
v1 = Vector[2,3,4]
v2 = Vector[4,5,6]
v1.covector.row_size #1
v1.covector.column_size #3
v2.covector.row_size #1
v2.covector.column_size #3
Vector does not have distinction between row and column, there's no column vector notion in the language.
v1 * v2.covector #Matrix[[8,10,12],[12,15,18],[16,20,24]]
# Should be illegal. But works like if v2.covector is transposed / column vector which it's clearly not.
v1.covector * v2.covector #ExceptionForMatrix::ErrDimensionMismatch: Matrix dimension mismatch
# Expected
v1 * v2 #ExceptionForMatrix::ErrOperationNotDefined: Operation(*) can't be defined: Vector op Vector
# No comments, see my observation below.
v1.covector * v2 #Vector[47]
#Again covector treated like transposed / column vector.
Personal observation: Terrible choice to represent Vector like an Array, Vector should be a shortcut to Matrix.
--
https://bugs.ruby-lang.org/
next prev parent reply other threads:[~2019-08-23 22:35 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <redmine.issue-12356.20160506235154@ruby-lang.org>
2016-05-06 23:51 ` [ruby-core:75394] [Ruby trunk Bug#12356] Vector covector incorrect multiplication with another vector rafael.soares81
2019-08-23 22:35 ` merch-redmine [this message]
2019-08-26 14:54 ` [ruby-core:94568] [Ruby master " ruby-core
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