Opened 5 years ago
Closed 5 years ago
#19418 closed enhancement (fixed)
skewHadamard matrices and related srg's
Reported by:  dimpase  Owned by:  

Priority:  major  Milestone:  sage6.10 
Component:  combinatorics  Keywords:  
Cc:  ncohen  Merged in:  
Authors:  Dima Pasechnik  Reviewers:  Nathann Cohen 
Report Upstream:  N/A  Work issues:  
Branch:  c50c78d (Commits)  Commit:  c50c78df2b1a236b32b42f5f3bf83d5f9d3b8015 
Dependencies:  #19309  Stopgaps: 
Description (last modified by )
implementing few basic constructions of skewHadamard matrices and 3 families of assoc. srg's.
Attachments (1)
Change History (56)
Changed 5 years ago by
comment:1 Changed 5 years ago by
 Cc ncohen added
comment:2 Changed 5 years ago by
 Commit changed from 347b37e0c1e3267c97fcb7680a6743b703fccfc8 to 3453e163484475d929f533cb9083b103d0f914ff
Branch pushed to git repo; I updated commit sha1. New commits:
3453e16  merged...

comment:3 Changed 5 years ago by
 Commit changed from 3453e163484475d929f533cb9083b103d0f914ff to bf8dcc10b89a99dfb97aa67005e2e9338e33d073
Branch pushed to git repo; I updated commit sha1. New commits:
bf8dcc1  added GoethalsSeidel construction; this gives orders 36 and 52

comment:4 Changed 5 years ago by
 Commit changed from bf8dcc10b89a99dfb97aa67005e2e9338e33d073 to 9e0ff0fb5380445d1fdac8a6828a878c77caf8bc
Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:
9e0ff0f  added GoethalsSeidel construction; this gives orders 36, 52, and 92

comment:5 Changed 5 years ago by
 Commit changed from 9e0ff0fb5380445d1fdac8a6828a878c77caf8bc to f4e3a06484b02a5990a2152426791d104e7b55b5
Branch pushed to git repo; I updated commit sha1. New commits:
f4e3a06  graph constructions added (prelim version, refs etc missing)

comment:6 Changed 5 years ago by
 Commit changed from f4e3a06484b02a5990a2152426791d104e7b55b5 to 4aa73f7cc4b503c3ad19cc77904a1a5e1e035cbb
Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:
4aa73f7  graph constructions added, with skewnormalizing Hadamard mats

comment:7 Changed 5 years ago by
 Description modified (diff)
 Status changed from new to needs_review
comment:8 Changed 5 years ago by
Hello Dima,
I just merged #19309 with the latest beta. Could you do *rebase* this branch on top of it (not merge) so that your commits appear on top of that other branch and are easier to review ?
Nathann
comment:9 Changed 5 years ago by
(right now the branch consists of 13 commits, 10 of which are merges with tickets that belong to the latest release)
comment:10 Changed 5 years ago by
I just did it: the rebased branch corresponding to this ticket can be found at public/19418.
Nathann
comment:11 Changed 5 years ago by
 Status changed from needs_review to needs_work
comment:12 Changed 5 years ago by
 Branch changed from u/dimpase/skewhad to public/19418
 Commit changed from 4aa73f7cc4b503c3ad19cc77904a1a5e1e035cbb to c5a7eee39d4c6dce006d1f6f8fd7a23383d540b7
 Status changed from needs_work to needs_review
New commits:
8607575  trac #19309: Polhill strongly regular graphs

2cd7910  trac #19309: Note for later

7bbefd1  trac #19309: Merged with 6.9.rc1

acba28b  trac #19309: Broken doctest

732f243  trac #19309: Merged with 6.10.beta0

e65da7e  trac #19309: Merged with 6.10.beta1

c5a7eee  trac #19418: skewHadamard matrices and related srg's

comment:13 Changed 5 years ago by
I assume you meant switching to this branch by 'work' :) By the way, I've left a function _L_g_n_params in the source (it's actually not used). If you think it should be removed, I will do so.
comment:14 followups: ↓ 15 ↓ 19 Changed 5 years ago by
 Reviewers set to Nathann Cohen
 Status changed from needs_review to needs_work
Helloooooo Dima,
Firstpass review:
 Why don't you call
normalise_hadamard
instead of adding a keyword inside ofhadamard_matrix_paleyI
(without changinghadamard_matrix_paleyII
)? Those two functions are not directly available to the users, who are meant to callhadamard_matrix
directly.
is_hadamard_martrix
 could you move 'skew=False' to before 'verbose=False' ? Usually the verbosity/check flags are the last ones to appear as they do not change the behaviour of the functon.
 Call
is_skew_symmetric
instead of doing it yourself. In theory you shouldn't have to create two copies of the matrix in memory in order to check that.
zero_position=1
 you have to write documentation for private functions too. Does [the paraeter that you add] appear in the lemma cited in the docstring?
zero_position=1
 if you meantTrue
, writeTrue
.
_circulant_matrix
 if it does not exist yet, this constructor should be added in the matrix/ code and be available throughmatrix.<tab>
mod(ji,n)
is(ji)%n
. One day you will have to accept that you write Python code.
 Instead of a
_GS_skew_hadamard
function that encodes 4 matrices, why don't you reserve cases `if n == 36' (and others) in the main functionskew_hadamard_matrix
? That would also solve the problem that this function has no documentation whatsoever.
 'and' (see wikipedia: https://en.wikipedia.org/wiki/Bitwise_operation#AND) is a useful operator in computer science. E.g.:
+ if M is None: # try WilliamsonGoethalsSeidel construction + if _GS_skew_hadamard(n, existence=True):
becomes
+ if M is None and_GS_skew_hadamard(n, existence=True):
switch_skewhad_pow2
 please respect the current standard for the names ingraphs.<tab>
. Upper case, no underscore, ends withGraph
. Actually, it could be named 'SwitchSkewhadGraph?and only mention the
pow2` part in the docstring.
graphs.Pseudo_L_2n_4n_m_1
? Seriously? If you cannot give it a clear and meaningful name easily, then take it as a sign that this function should not be exposed to the users directly.
_L_g_n_params
 yes, please remove this function if you do not use it.
Nathann
comment:15 in reply to: ↑ 14 ; followup: ↓ 17 Changed 5 years ago by
Replying to ncohen:
Firstpass review:
thanks, and apologies for sloppy code (back to Oxford with huge jetlag)
 Why don't you call
normalise_hadamard
instead of adding a keyword inside ofhadamard_matrix_paleyI
(without changinghadamard_matrix_paleyII
)? Those two functions are not directly available to the users, who are meant to callhadamard_matrix
directly.
normalize_hadamard
does not do what I need; I need a different type of normalization, in fact, where the matrix has the 1st row consisting of 1s, and still H+H.T==2*I,
i.e. the 1st column of H is all 1 (with exception of the top left entry)
Should I perhaps introduce skew_normalize_hadamard
,
that can only be applied to skew Hadamard matrices?
(I'd have uses for it in graph constructions, too)
is_hadamard_martrix
 could you move 'skew=False' to before 'verbose=False' ? Usually the verbosity/check flags are the last ones to appear as they do not change the behaviour of the functon.
right. I forgot that keyword args can be positional, too...
 Call
is_skew_symmetric
instead of doing it yourself. In theory you shouldn't have to create two copies of the matrix in memory in order to check that.
zero_position=1
 you have to write documentation for private functions too. Does [the paraeter that you add] appear in the lemma cited in the docstring?
zero_position=1
 if you meantTrue
, writeTrue
.
_circulant_matrix
 if it does not exist yet, this constructor should be added in the matrix/ code and be available throughmatrix.<tab>
OK
mod(ji,n)
is(ji)%n
. One day you will have to accept that you write Python code.
 Instead of a
_GS_skew_hadamard
function that encodes 4 matrices, why don't you reserve cases `if n == 36' (and others) in the main functionskew_hadamard_matrix
? That would also solve the problem that this function has no documentation whatsoever.
I'd rather add documentation, thanks for reminding.
I find skew_hadamard_matrix
already hard to read, and
it would positively turn ugly if I start adding that explicit data for matrices there.
 'and' (see wikipedia: https://en.wikipedia.org/wiki/Bitwise_operation#AND) is a useful operator in computer science. E.g.:
+ if M is None: # try WilliamsonGoethalsSeidel construction + if _GS_skew_hadamard(n, existence=True):becomes
+ if M is None and_GS_skew_hadamard(n, existence=True):
oops  there is an extra if
there that should go...
switch_skewhad_pow2
 please respect the current standard for the names ingraphs.<tab>
. Upper case, no underscore, ends withGraph
. Actually, it could be named 'SwitchSkewhadGraph?and only mention the
pow2` part in the docstring.
graphs.Pseudo_L_2n_4n_m_1
? Seriously? If you cannot give it a clear and meaningful name easily, then take it as a sign that this function should not be exposed to the users directly.
How about we have a PseudoLatinSquaresGraph(m,n)
or PseudoOrthogonalArrayBlockGraph(m,n)
? (I'd prefer the former name; or maybe we can have both?)
It would include Pseudo_L_2n_4n_m_1
and OrthogonalArrayBlockGraph
as subcases.
(Perhaps there are more subcases, in fact, but we don't have to worry about it now).
_L_g_n_params
 yes, please remove this function if you do not use it.
sure.
comment:16 Changed 5 years ago by
 Dependencies set to #19309
comment:17 in reply to: ↑ 15 ; followup: ↓ 18 Changed 5 years ago by
Helloooooooooooooooooooo,
(back to Oxford with huge jetlag)
Wow. Common timezone again. Cool ;)
normalize_hadamard
does not do what I need; I need a different type of normalization, in fact, where the matrix has the 1st row consisting of 1s, and still H+H.T==2*I, i.e. the 1st column of H is all 1 (with exception of the top left entry)Should I perhaps introduce
skew_normalize_hadamard
, that can only be applied to skew Hadamard matrices? (I'd have uses for it in graph constructions, too)
Sounds right. Then you can have a proper documentation and stuff. If you plan to use it elsewhere that's even better.
I'd rather add documentation, thanks for reminding. I find
skew_hadamard_matrix
already hard to read, and it would positively turn ugly if I start adding that explicit data for matrices there.
Okayokay.
How about we have a
PseudoLatinSquaresGraph(m,n)
orPseudoOrthogonalArrayBlockGraph(m,n)
? (I'd prefer the former name; or maybe we can have both?)
+1 to the former. With a description of what it is in its doc, if possible ^^;
Nathann
comment:18 in reply to: ↑ 17 ; followup: ↓ 20 Changed 5 years ago by
Replying to ncohen:
(back to Oxford with huge jetlag)
Wow. Common timezone again. Cool
;)
an hour difference, still :)
normalize_hadamard
does not do what I need; I need a different type of normalization, in fact, where the matrix has the 1st row consisting of 1s, and still H+H.T==2*I, i.e. the 1st column of H is all 1 (with exception of the top left entry)Should I perhaps introduce
skew_normalize_hadamard
, that can only be applied to skew Hadamard matrices? (I'd have uses for it in graph constructions, too)Sounds right. Then you can have a proper documentation and stuff. If you plan to use it elsewhere that's even better.
oops, this won't fly. The problem is that once a skewHadamard matrix was deskewed (e.g. by the usual normalization procedure, producing the 1st row and column of 1s), there is no general way known to make it skew again. (and in fact not every Hadamard matrix can be made skew, AFAIK).
That is, I have to disable normalization right at the point it is done in hadamard_matrix_paleyI
. (writing an ad hoc code to undo this specific normalization seems silly).
comment:19 in reply to: ↑ 14 Changed 5 years ago by
Replying to ncohen:
Helloooooo Dima,
Firstpass review:
 Why don't you call
normalise_hadamard
instead of adding a keyword inside ofhadamard_matrix_paleyI
(without changinghadamard_matrix_paleyII
)? Those two functions are not directly available to the users, who are meant to callhadamard_matrix
directly.
is_hadamard_martrix
 could you move 'skew=False' to before 'verbose=False' ? Usually the verbosity/check flags are the last ones to appear as they do not change the behaviour of the functon.
 Call
is_skew_symmetric
instead of doing it yourself. In theory you shouldn't have to create two copies of the matrix in memory in order to check that.
this won't fly either, as a skew Hadamard matrix H is not skewsymmetric. What is skewsymmetric is the matrix HI, so it has to be created anyway
(by the way, this explains why making a Hadamard matrix skew is not too obvious; indeed,
the trick mentioned in the docs of is_skew_symmetrizable
would only work if H had
constant diagonal.)
comment:20 in reply to: ↑ 18 Changed 5 years ago by
Yo,
oops, this won't fly. The problem is that once a skewHadamard matrix was deskewed (e.g. by the usual normalization procedure, producing the 1st row and column of 1s), there is no general way known to make it skew again. (and in fact not every Hadamard matrix can be made skew, AFAIK).
That is, I have to disable normalization right at the point it is done in
hadamard_matrix_paleyI
. (writing an ad hoc code to undo this specific normalization seems silly).
I cannot say that I understand what you have in mind, but as long as what happens is made clear in the documentation I guess that it is okay.
this won't fly either, as a skew Hadamard matrix H is not skewsymmetric. What is skewsymmetric is the matrix HI, so it has to be created anyway
Then create HI, but don't create S nor S.T.
Nathann
comment:21 Changed 5 years ago by
 Commit changed from c5a7eee39d4c6dce006d1f6f8fd7a23383d540b7 to c284eda90adb73aa4e0a36e0d6467fb76c779654
comment:22 followup: ↓ 23 Changed 5 years ago by
a couple of remarks about the last commit:
 except without the name of a specific exception makes Jeroen scream.
 It is a weird that the value of 'sparse' is ignored when 'v.is_sparse' says otherwise. The expected behaviour would be sparse=None by default (auto detect) and use the userprovided value otherwise.
comment:23 in reply to: ↑ 22 ; followup: ↓ 33 Changed 5 years ago by
Replying to ncohen:
a couple of remarks about the last commit:
 except without the name of a specific exception makes Jeroen scream.
OK, sure, I will make it catch NoneType
 It is a weird that the value of 'sparse' is ignored when 'v.is_sparse' says otherwise. The expected behaviour would be sparse=None by default (auto detect) and use the userprovided value otherwise.
I want to implement something like this:
def f(vector v): stuff... def f(list v, sparse=False): stuff...
and this is what my code does.
The userprovided value of sparse for vector v
is present in v
already.
If the user wants to make it explicit, he can call the function with the
parameter vector(v, sparse=whatever)
instead of just v
comment:24 Changed 5 years ago by
 Commit changed from c284eda90adb73aa4e0a36e0d6467fb76c779654 to 6f5488747fe670975c27d262711b6561fda7c548
Branch pushed to git repo; I updated commit sha1. New commits:
6f54887  function renaming, documenting, and doctesting, and removing extra if

comment:25 Changed 5 years ago by
 Commit changed from 6f5488747fe670975c27d262711b6561fda7c548 to 6b80f002f5e13f9d165e7ffc41fb984110d6c36a
Branch pushed to git repo; I updated commit sha1. New commits:
6b80f00  added AttributeError to check for in except:

comment:26 Changed 5 years ago by
 Commit changed from 6b80f002f5e13f9d165e7ffc41fb984110d6c36a to c04916b8e3924ff6da6066185cee62148ecf20c8
comment:27 Changed 5 years ago by
 Status changed from needs_work to needs_review
looks like I have addressed all the points raised; (I didn't mention in commit messages that the code now does checking of skewHadamardness inplace). ready for another round, hopefully...
New commits:
135c0ea  for a skew Hadamard matrix, check that the diagonal entries are all 1

c04916b  return skewnormalized Hadamard mats by default

comment:28 Changed 5 years ago by
 Commit changed from c04916b8e3924ff6da6066185cee62148ecf20c8 to 535e1096291f0c2fdc34b5b28cf5f6728ed76fa1
Branch pushed to git repo; I updated commit sha1. New commits:
535e109  putting reference in the right file

comment:29 Changed 5 years ago by
now make docclean && make
passes.
comment:30 Changed 5 years ago by
 Commit changed from 535e1096291f0c2fdc34b5b28cf5f6728ed76fa1 to b3fb30b3c62a11a0609d578e8f71f706c220d24e
Branch pushed to git repo; I updated commit sha1. New commits:
b3fb30b  Merge branch 'develop' of git://trac.sagemath.org/sage into skewhad

comment:31 followup: ↓ 32 Changed 5 years ago by
 Commit changed from b3fb30b3c62a11a0609d578e8f71f706c220d24e to 01763fd38506f8721560fa29e60227e5081db08b
Branch pushed to git repo; I updated commit sha1. New commits:
01763fd  remove #random from paleyI/II and fix the test

comment:32 in reply to: ↑ 31 Changed 5 years ago by
comment:33 in reply to: ↑ 23 Changed 5 years ago by
I want to implement something like this:
def f(vector v): stuff... def f(list v, sparse=False): stuff...and this is what my code does.
The userprovided value of sparse for vector
v
is present inv
already. If the user wants to make it explicit, he can call the function with the parametervector(v, sparse=whatever)
instead of justv
Usually the explicit value overrides the implicit value:
sage: Graph(graphs.PetersenGraph())._backend <type 'sage.graphs.base.sparse_graph.SparseGraphBackend'> sage: Graph(graphs.PetersenGraph(),sparse=False)._backend <type 'sage.graphs.base.dense_graph.DenseGraphBackend'>
It is not the case in your code.
Nathann
comment:34 followup: ↓ 35 Changed 5 years ago by
could be something like that
def thing(v,sparse=None): if sparse is None: try: sparse = v.is_sparse() except AttributeError: sparse = False
comment:35 in reply to: ↑ 34 Changed 5 years ago by
Replying to ncohen:
could be something like that
def thing(v,sparse=None): if sparse is None: try: sparse = v.is_sparse() except AttributeError: sparse = False
I'll be happy to fix it as you prefer. (You could also add a commit, of course :))
comment:36 Changed 5 years ago by
Okayokay. Well I'm reviewing the code at the moment.
By the way on my way to here I finished a wonderful script that extracts tables from a pdf file. Some french guys need that to turn into open data what the government releases to feel open (i.e. ugly pdf files).
But we'll show 'em.
Nathann
comment:37 followups: ↓ 38 ↓ 40 Changed 5 years ago by
 Status changed from needs_review to needs_work
Helloooooooooo Dima,
Here is another pass:
 I don't think that you need to import functions at the top of every single '::' block. If you imported them in a previous doctest of the same function they are usually around. I say 'usually' because I don't think I read that anywhere, but it just works. If the order in which doctests are run can be 'random', I think that it just shuffles the functions and not the doctests inside of a function.
 docstring of zero_position: bad alignment of 'place it first'. Misses one space.
 Same line: the sentence is not complete  what about adding 'When it' at its beginning?
 You did not doctest your new flag. Also, the code *looks* wrong.
 Docstring of
williamson_goethals_seidel_skew_hadamard_matrix
. Things seem to miss from the first sentence of the paragraph. Or it's me being sick again. P.S.: syntactically, a ')' is missing at least.
 Same function. The following doc should be in the function that actually
returns those matrices:
+ Matrices for `n=36` and `52` are given in [GS70s]_. Matrices for `n=92` are given + in [Wall71]_.
_GS_skew_hadamard
 the name of that function is a bit too vague. What aboutGS_skew_hadamard_smallcases
? You don't necessarily need to make it private, by the way. It lives in a module and does not appear in the global namespace, so only the interested guys will find it. And it's not technically complicated to use, the input/output is well defined and reliable. It can't be misused.
 private functions need doctests too. 'cdef' is the only situation in which you don't need them.
def pmtoZ(s):
could be defined in the only 'if' that requires it (not very important).
 docstring of
skew_hadamard_matrix
 in the block of doc about 'existence', one reads 'but that design does not exist'. Could you replace 'design' by 'matrix'?
 I don't see why the following doctest has a 'long' flag
sage: skew_hadamard_matrix(784,existence=True) # long time
If you actually built the matrix, however, that would be correct.
 I don't think that
check=False
is useful whenexistence=True
skew_hadamard_matrix(n//2,existence=True, check=False)
 In the
n%8==0
case you implement the product construction of skew hadamard matrices with a 2x2 matrix only. Is there a reason to that?
if _GS_skew_hadamard(n, existence=True)
 it hardly matters, but it would be 'cleaner' to call this (quick) function before checking the more complicated (recursive) constructions.
 Shouldn't you also check that the matrix is 'skewnormalized', as we do with
the regular normalization?
+ if skew_normalize: + dd = diagonal_matrix(M[0]) + M = dd*M*dd + if check: + assert is_hadamard_matrix(M, normalized=False, skew=True)
 If you are too humble to do it yourself, I will change that to 'Return the
Pasechnik graph of order n'
:)
+ Pseudo`OA(2n1,4n1)`graph from a skew Hadamard matrix of order `4n`
 Please add your new graphs to the
graphs.<tab>
constructor.
Nathann
comment:38 in reply to: ↑ 37 Changed 5 years ago by
Replying to ncohen:
 In the
n%8==0
case you implement the product construction of skew hadamard matrices with a 2x2 matrix only. Is there a reason to that?
huh? I have there
elif n % 8 == 0: if skew_hadamard_matrix(n//2,existence=True, check=False): if existence: return true() H = skew_hadamard_matrix(n//2,check=False) M = block_matrix([[H,H], [H.T,H.T]]) else: # try Williamson construction for d in divisors(n)[2:2]: # skip 1, 2, n/2, and n ... more stuff
so I first check if I can multiply with 2x2 matrix, and if not, I try Williamson construction
.
comment:39 Changed 5 years ago by
 Commit changed from 01763fd38506f8721560fa29e60227e5081db08b to 3503d6218c68b2d1f8e08ffe832daeb0c4b393d4
comment:40 in reply to: ↑ 37 Changed 5 years ago by
Replying to ncohen:
 I don't think that you need to import functions at the top of every single '::' block. If you imported them in a previous doctest of the same function they are usually around. I say 'usually' because I don't think I read that anywhere, but it just works. If the order in which doctests are run can be 'random', I think that it just shuffles the functions and not the doctests inside of a function.
OK. Removed some of these...
 docstring of zero_position: bad alignment of 'place it first'. Misses one space.
 Same line: the sentence is not complete  what about adding 'When it' at its beginning?
 You did not doctest your new flag. Also, the code *looks* wrong.
well, actually in this case the code is not doing what is advertised; without my flag the matrix for n=4k1 is not symmetric w.r.t. the antidiagonal; the submatrix obtained by removal of the 1st row and the 1st column is symmetric w.r.t. the antidiagonal. I changed the doc accordingly. And added a doctest.
 Docstring of
williamson_goethals_seidel_skew_hadamard_matrix
. Things seem to miss from the first sentence of the paragraph. Or it's me being sick again. P.S.: syntactically, a ')' is missing at least.
fixed.
 Same function. The following doc should be in the function that actually returns those matrices:
+ Matrices for `n=36` and `52` are given in [GS70s]_. Matrices for `n=92` are given + in [Wall71]_.
moved
_GS_skew_hadamard
 the name of that function is a bit too vague. What aboutGS_skew_hadamard_smallcases
? You don't necessarily need to make it private, by the way. It lives in a module and does not appear in the global namespace, so only the interested guys will find it. And it's not technically complicated to use, the input/output is well defined and reliable. It can't be misused.
renamed as you proposed.
 private functions need doctests too. 'cdef' is the only situation in which you don't need them.
OK, OK... added
def pmtoZ(s):
could be defined in the only 'if' that requires it (not very important).
well, if we added more data in +  format, it would be at the right place as it is.
 docstring of
skew_hadamard_matrix
 in the block of doc about 'existence', one reads 'but that design does not exist'. Could you replace 'design' by 'matrix'?
done
 I don't see why the following doctest has a 'long' flag
sage: skew_hadamard_matrix(784,existence=True) # long timeIf you actually built the matrix, however, that would be correct.
good catch  fixed
 I don't think that
check=False
is useful whenexistence=True
skew_hadamard_matrix(n//2,existence=True, check=False)
uh oh... fixed.
if _GS_skew_hadamard(n, existence=True)
 it hardly matters, but it would be 'cleaner' to call this (quick) function before checking the more complicated (recursive) constructions.
Oh, well, if you feel like changing this, go ahead...
 Shouldn't you also check that the matrix is 'skewnormalized', as we do with the regular normalization?
+ if skew_normalize: + dd = diagonal_matrix(M[0]) + M = dd*M*dd + if check: + assert is_hadamard_matrix(M, normalized=False, skew=True)
added a check.
 If you are too humble to do it yourself, I will change that to 'Return the Pasechnik graph of order n'
:)
+ Pseudo`OA(2n1,4n1)`graph from a skew Hadamard matrix of order `4n`
if you must...
 Please add your new graphs to the
graphs.<tab>
constructor.
actually, I removed them, but I'll add them again...
New commits:
fd7894a  check that skew_normalize worked

3503d62  rest of fixes for hadamard_matrix.py

New commits:
fd7894a  check that skew_normalize worked

3503d62  rest of fixes for hadamard_matrix.py

comment:41 Changed 5 years ago by
 Commit changed from 3503d6218c68b2d1f8e08ffe832daeb0c4b393d4 to 595f7e9f55f9566a315394df4f998a56e3dfab40
Branch pushed to git repo; I updated commit sha1. New commits:
595f7e9  added graphs to graphs.<tab>, and doc(test)s additions and fixes

comment:42 Changed 5 years ago by
 Status changed from needs_work to needs_review
comment:43 Changed 5 years ago by
 Status changed from needs_review to needs_work
sage: skew_hadamard_matrix(816) ... TypeError: unsupported operand parent(s) for '*': 'Full MatrixSpace of 12 by 12 dense matrices over Integer Ring' and 'Full MatrixSpace of 68 by 68 dense matrices over Integer Ring'
comment:44 followup: ↓ 46 Changed 5 years ago by
Can you tell me why you apparently refuse my request about the behaviour of 'sparse' in 'circulant'?
Nathann
comment:45 Changed 5 years ago by
 Commit changed from 595f7e9f55f9566a315394df4f998a56e3dfab40 to 06fd9b4212d1a64448df1cbb39ba53b72865c3d1
Branch pushed to git repo; I updated commit sha1. New commits:
06fd9b4  fix the bug, and add docs

comment:46 in reply to: ↑ 44 Changed 5 years ago by
Replying to ncohen:
Can you tell me why you apparently refuse my request about the behaviour of 'sparse' in 'circulant'?
oops  forgot about it. Tonight I'll have more time to look at it.
The last commit fixes the n=816 bug (facepalm)  thanks for the example. I checked now the values of n up to 1200, they appears to work fine...
comment:47 Changed 5 years ago by
Okayyy. Thanks for the fix ;)
comment:48 Changed 5 years ago by
 Commit changed from 06fd9b4212d1a64448df1cbb39ba53b72865c3d1 to c50c78df2b1a236b32b42f5f3bf83d5f9d3b8015
Branch pushed to git repo; I updated commit sha1. New commits:
c50c78d  fixing circulant's behaviour

comment:49 Changed 5 years ago by
 Status changed from needs_work to needs_review
comment:50 Changed 5 years ago by
Okayyyyyyyyyyyy... Thanks for this branch ! ;)
Nathann
comment:51 Changed 5 years ago by
OK, with all the changes, patchbots (most of them) seem to be happy. And the reviewer?
comment:52 Changed 5 years ago by
 Status changed from needs_review to positive_review
He's happy too.
comment:53 followup: ↓ 54 Changed 5 years ago by
Thanks! By the way, _check_database() now says for me:
... Sage can build a (1024, 462, 206, 210), Brouwer's database cannot Sage can build a (1024, 561, 308, 306), Brouwer's database cannot In Andries Brouwer's database:  448 impossible entries  2950 undecided entries  1140 realizable entries (Sage misses 36 of them)
On the other hand the graphs above can be found in http://www.win.tue.nl/~aeb/graphs/srg/srgtab10011050.html Does it mean that Sage's copy of the DB needs an update?
OK, so should I next take out Mathon's v=45?
comment:54 in reply to: ↑ 53 Changed 5 years ago by
Does it mean that Sage's copy of the DB needs an update?
Yes. We gave him info to update his database but we didn't update our copy. By the way, the difference between our copy and his can be seen as 'one of the sideeffects' of the work we have been doing. We may need that info.
OK, so should I next take out Mathon's v=45?
Take as many as you can out. I don't think that there is any left that I can implement: those that I thought manageable were apparently wrong constructions, and the authors 'play dead'.
Nathann
comment:55 Changed 5 years ago by
 Branch changed from public/19418 to c50c78df2b1a236b32b42f5f3bf83d5f9d3b8015
 Resolution set to fixed
 Status changed from positive_review to closed
a draft implementation of the corresponding SRGs