Very careless typoes in strongly_regular_db

[nathanncohen]

This branch fixes very bad typoes in that file, that made several constructions useless or broken. Mostly missing characters (emacs macros...)

Nathann

Depends on #19018

CC: @dimpase

Component: graph theory

Author: Nathann Cohen

Branch: cb0b3fb

Reviewer: Dima Pasechnik

Issue created by migration from https://trac.sagemath.org/ticket/19019

[nathanncohen]

Branch: u/ncohen/19019

[sagetrac-git]

Commit: 05b2fa8

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

a414c36	trac #19018: More SRGs using Regular Symmetric Hadamard matric with Constant Diagonal
05b2fa8	trac #19019: Very careless typoes in strongly_regular_db

[jm58660]

comment:3

Not relating to just this patch, but why functions like SRG_100_44_18_20(), SRG_100_45_20_20() etc. instead of something like SRG_from_db(100, 44, 18, 20)? There might be some rationale explained in some other ticket.

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

c430b4b	trac #19018: Link the new constructions with graphs.strongly_regular_graph
0e533bb	trac #19018: Bibliography
4abbce4	trac #19019: Very careless typoes in strongly_regular_db

[sagetrac-git]

Changed commit from 05b2fa8 to 4abbce4

[nathanncohen]

comment:5

Not relating to just this patch, but why functions like SRG_100_44_18_20(), SRG_100_45_20_20() etc. instead of something like SRG_from_db(100, 44, 18, 20)? There might be some rationale explained in some other ticket.

I do not understand what you mean, and I do not want the conversation to happen on this unrelated ticket. Please send me an email or write to sage-devel.

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

c5e24be

trac #19019: Missing space

[sagetrac-git]

Changed commit from 4abbce4 to c5e24be

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

6893ad1	trac #19018: Typo
e18bee7	trac #19019: Very careless typoes in strongly_regular_db
3f76966	trac #19019: Missing space

[sagetrac-git]

Changed commit from c5e24be to 3f76966

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

d66f0b6	trac #19018: Specify which graph is built
1cae2dc	trac #19028: Table 8.1
7045124	trac #19018: Merged with 6.9.beta2
99fa6ce	trac #19019: Very careless typoes in strongly_regular_db
cb071e2	trac #19019: Missing space
19b40d9	trac #19019: Sort the list of SRGs

[sagetrac-git]

Changed commit from 3f76966 to 19b40d9

[dimpase]

Changed branch from u/ncohen/19019 to public/19019

[dimpase]

comment:9

rebased over the latest developments on #19018. LGTM

[dimpase]

Changed commit from 19b40d9 to 778556f

[jm58660]

comment:10

Volker will reject this if you don't add your name to Reviewers-field.

[sagetrac-git]

Changed commit from 778556f to 323416f

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1 and set ticket back to needs_review. New commits:

323416f

added a doctest

[dimpase]

comment:12

Replying to @sagetrac-git:

Branch pushed to git repo; I updated commit sha1 and set ticket back to needs_review. New commits:

323416f

added a doctest

rebased over the latest #19018 branch

[dimpase]

comment:15

I cannot find the extra commit in question.

[dimpase]

Reviewer: Dima Pasechnik

[nathanncohen]

comment:16

It is the last commit of this branch.

[dimpase]

comment:17

In the local branch I do not have 2 copies of this commit. Naturally, if I were to remove it and push the result then it would not be there at all.

[nathanncohen]

comment:18

In the local branch you have this commit. In the branch of #19018 you have another copy of it. Because you cherry-picked it, when the two branches will be merged you will have two copies of it.

This commit belongs to the other branch, not to that one. If you remove it from this branch, it will be in Sage when #19018 will be merged.

You should have merged the branches, not cherry-picked the commit.

Nathann

[sagetrac-git]

Changed commit from 323416f to cb0b3fb

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1 and set ticket back to needs_review. This was a forced push. New commits:

6ed716d	added a doctest
cb0b3fb	Merge branch 'reg_symm_hadamard' into t19019

[dimpase]

comment:20

please review these git things. I'll be offline for the coming 10 hours.

[nathanncohen]

comment:21

Looks good, thanks.

Nathann

[vbraun]

Changed branch from public/19019 to cb0b3fb

[dimpase]

comment:23

I overlooked

+    When `\epsilon\in\{-1,+1\}`, we say that `M` is a `(n,\epsilon)-RSHCD` if
+    `M` is a regular symmetric Hadamard matrix with constant diagonal
+    `\delta\in\{-1,+1\}` and row values all equal to `\delta \epsilon
+    \sqrt(n)`. For more information, see [HX10]_ or 10.5.1 in
+    [BH12]_.

• what are "row values"? row sums?
• the definition of RSHCD here does not match one in [BH12], where the diagonal entries are all 1, and (n,e)-RSHCD has row sums e\sqrt{n}.
• it should be \sqrt{n}, not \sqrt(n)

And another thing - RSHCD should be mentioned in the module description in the beginning of the corr. file.

[dimpase]

Changed commit from cb0b3fb to none

[nathanncohen]

comment:24

• what are "row values"? row sums?

Arg... Yes. Row sums.

• the definition of RSHCD here does not match one in [BH12], where the diagonal entries are all 1, and (n,e)-RSHCD has row sums e\sqrt{n}.

So what do we do? With two papers that say contradictory things?

• it should be \sqrt{n}, not \sqrt(n)

Right.

And another thing - RSHCD should be mentioned in the module description in the beginning of the corr. file.

I don't understand.

Nathann

[jm58660]

comment:25

Replying to @nathanncohen:

So what do we do? With two papers that say contradictory things?

IMO select one and (almost) always document these cases. See chain_polynomial() on posets: "Warning: This is not what has been called the chain polynomial in [St1986]. The latter is - -".

[nathanncohen]

comment:26

IMO select one and (almost) always document these cases. See chain_polynomial() on posets: "Warning: This is not what has been called the chain polynomial in [St1986]. The latter is - -".

Jori, this was a rethoric question. The two definitions agree with each other.

[dimpase]

comment:27

Replying to @nathanncohen:

• the definition of RSHCD here does not match one in [BH12], where the diagonal entries are all 1, and (n,e)-RSHCD has row sums e\sqrt{n}.

So what do we do? With two papers that say contradictory things?

I was comparing your definition with the one from
http://homepages.cwi.nl/~aeb/math/ipm/ipm.pdf
and your definition is more complicated.
I did not check the other one.

And another thing - RSHCD should be mentioned in the module description in the beginning of the corr. file.

I don't understand.

If look at combinat/matrices/hadamard_matrix.py there is a paragraph saying

The module below implements the Paley constructions (see for example
[Hora]_) and the Sylvester construction. It also allows you to pull a
Hadamard matrix from the database at [HadaSloa]_.

But there is no word about RSHCDs.
Should it instead get a list of methods, etc, as more modern Sage modules have?

As well, you're not in the list of authors.

As I am gearing up for skew-Hadamard matrices, it can be done on the corresponding ticket.

[nathanncohen]

comment:28

I was comparing your definition with the one from
http://homepages.cwi.nl/~aeb/math/ipm/ipm.pdf
and your definition is more complicated.
I did not check the other one.

I don't see how. In the paper you give the matrix is requested to have 1 on the diagonal, that's the only difference I see.

If look at combinat/matrices/hadamard_matrix.py there is a paragraph saying
But there is no word about RSHCDs.

Oh, right. I'll do that.

Should it instead get a list of methods, etc, as more modern Sage modules have?

Probably. I am working on a patch related to index of functions at the moment, though. Something to make building a thematic index easier.

As well, you're not in the list of authors.

How I hate this "I am the one who did it" bullshit...

As I am gearing up for skew-Hadamard matrices, it can be done on the corresponding ticket.

Skew-hadamard? sigh.... Someday we will have all kind of designs in Sage. But today is not this day.

Nathann

[dimpase]

comment:29

Replying to @nathanncohen:

I was comparing your definition with the one from
http://homepages.cwi.nl/~aeb/math/ipm/ipm.pdf
and your definition is more complicated.
I did not check the other one.

I don't see how. In the paper you give the matrix is requested to have 1 on the diagonal, that's the only difference I see.

yes, this is the difference that makes your definition different.
I suppose this is very close to the original one, as all is needed is multiplication by -1 to convert one into the other. But still not the same...

As well, you're not in the list of authors.

How I hate this "I am the one who did it" bullshit...

well, if only for uniformity...

As I am gearing up for skew-Hadamard matrices, it can be done on the corresponding ticket.

Skew-hadamard? sigh.... Someday we will have all kind of designs in Sage. But today is not this day.

we need them to build "skewhad*" and your humble servant srg's, as I already mentioned.

[nathanncohen]

comment:30

yes, this is the difference that makes your definition different.
I suppose this is very close to the original one, as all is needed is multiplication by -1 to convert one into the other. But still not the same...

For all practical purposes it is the same. One says that the diagonal has to be 1, the other says that it can be -1 but adapts the value of row sums. If you get one which does not have a 1 on the diagonal, then -your_matrix does the job, and all results of existence/non-existence apply.

Nathann