eja: factor out a class for real-embedded matrices.

[sage.d.git] / mjo / eja / TODO

diff --git a/mjo/eja/TODO b/mjo/eja/TODO
index feaf98ac872145accaa4788419dddd325fde917b..13b00ac6a3056eaf623ac5c2905be6c7d049706c 100644 (file)
--- a/mjo/eja/TODO
+++ b/mjo/eja/TODO
@@ -2,7 +2,8 @@
 
 2. Add references and start citing them.
 
-3. Implement the octonion simple EJA.
+3. Implement the octonion simple EJA. We don't actually need octonions
+   for this to work, only their real embedding (some 8x8 monstrosity).
 
 4. Pre-cache charpoly for some small algebras?
 
@@ -15,15 +16,22 @@ sage: a0 = (1/4)*X[4]**2*X[6]**2 - (1/2)*X[2]*X[5]*X[6]**2 - (1/2)*X[3]*X[4]*X[6
    15-dimensional QuaternionHermitianAlgebra(3)) to find out why
    they're so slow.
 
-6. We should compute whether or not the algebra is associative if it
-   is unknown. I guess the "associative" argument should be ternary
-   (True, False, None)? We should also figure out the correct
-   True/False values for the example classes, and of course add an
-   _is_associative() method.
+6. Instead of storing a basis multiplication matrix, just make
+   product_on_basis() a cached method and manually cache its
+   entries. The cython cached method lookup should be faster than a
+   python-based matrix lookup anyway.
 
-7. When field=RDF, subalgebra construction is failing because the
-   inner product isn't associative? Actually, it's the combination
-   of field=RDF and orthonormalize=True.
+7. What the ever-loving fuck is this shit?
 
-8. Set check_axioms=False for element-subalgebras outside of once or
-   twice in the test suite.
+       sage: O = Octonions(QQ)
+       sage: e0 = O.monomial(0)
+       sage: e0*[[[[]]]]
+       [[[[]]]]*e0
+
+8. In fact, could my octonion matrix algebra be generalized for any
+   algebra of matrices over the reals whose entries are not real? Then
+   we wouldn't need real embeddings at all. They might even be fricking
+   vector spaces if I did that...
+
+9. Add HurwitzMatrixAlgebra subclass between MatrixAlgebra and
+   OctonionMatrixAlgebra.