From: Michael Orlitzky <michael@orlitzky.com>
Date: Fri, 12 Mar 2021 02:57:16 +0000 (-0500)
Subject: eja: cache the span of the matrix basis when written out as long vectors.
X-Git-Url: http://gitweb.michael.orlitzky.com/?p=sage.d.git;a=commitdiff_plain;h=fd6a4ce03de36bb2551160e08440b0c0049746e1

eja: cache the span of the matrix basis when written out as long vectors.

This GREATLY improves the speed of the _element_constructor_(), and
therefore of Cartesian products.
---

diff --git a/mjo/eja/eja_algebra.py b/mjo/eja/eja_algebra.py
index ee2b526..5e2c315 100644
--- a/mjo/eja/eja_algebra.py
+++ b/mjo/eja/eja_algebra.py
@@ -347,14 +347,19 @@ class FiniteDimensionalEJA(CombinatorialFreeModule):
         # its own set of non-ambient coordinates (in terms of the
         # supplied basis).
         vector_basis = tuple( V(_all2list(b)) for b in basis )
-        W = V.span_of_basis( vector_basis, check=check_axioms)
+
+        # Save the span of our matrix basis (when written out as long
+        # vectors) because otherwise we'll have to reconstruct it
+        # every time we want to coerce a matrix into the algebra.
+        self._matrix_span = V.span_of_basis( vector_basis, check=check_axioms)
 
         if orthonormalize:
-            # Now "W" is the vector space of our algebra coordinates. The
-            # variables "X1", "X2",...  refer to the entries of vectors in
-            # W. Thus to convert back and forth between the orthonormal
-            # coordinates and the given ones, we need to stick the original
-            # basis in W.
+            # Now "self._matrix_span" is the vector space of our
+            # algebra coordinates. The variables "X1", "X2",...  refer
+            # to the entries of vectors in self._matrix_span. Thus to
+            # convert back and forth between the orthonormal
+            # coordinates and the given ones, we need to stick the
+            # original basis in self._matrix_span.
             U = V.span_of_basis( deortho_vector_basis, check=check_axioms)
             self._deortho_matrix = matrix.column( U.coordinate_vector(q)
                                                   for q in vector_basis )
@@ -378,7 +383,7 @@ class FiniteDimensionalEJA(CombinatorialFreeModule):
                 # The jordan product returns a matrixy answer, so we
                 # have to convert it to the algebra coordinates.
                 elt = jordan_product(q_i, q_j)
-                elt = W.coordinate_vector(V(_all2list(elt)))
+                elt = self._matrix_span.coordinate_vector(V(_all2list(elt)))
                 self._multiplication_table[i][j] = self.from_vector(elt)
 
                 if not orthonormalize:
@@ -781,15 +786,10 @@ class FiniteDimensionalEJA(CombinatorialFreeModule):
         # is that we're already converting everything to long vectors,
         # and that strategy works for tuples as well.
         #
-        # We pass check=False because the matrix basis is "guaranteed"
-        # to be linearly independent... right? Ha ha.
-        elt = _all2list(elt)
-        V = VectorSpace(self.base_ring(), len(elt))
-        W = V.span_of_basis( (V(_all2list(s)) for s in self.matrix_basis()),
-                             check=False)
+        elt = self._matrix_span.ambient_vector_space()(_all2list(elt))
 
         try:
-            coords = W.coordinate_vector(V(elt))
+            coords = self._matrix_span.coordinate_vector(elt)
         except ArithmeticError:  # vector is not in free module
             raise ValueError(msg)