Ticket #8096: 8096-zero-matrix.patch

sage/matrix/matrix_space.py

@@ -342 +342 @@
             [1 1]
             [0 1]
         """
-        if entries is None:
-            entries = 0
-
-        if entries == 0 and hasattr(self, '__zero_matrix'):
+        if entries is None or entries == 0:
             return self.zero_matrix()
 
         if isinstance(entries, (list, tuple)) and len(entries) > 0 and \
@@ -1016 +1013 @@
         try:
             z = self.__zero_matrix
         except AttributeError:
-            z = self(0)
+            z = self.matrix(0)
             self.__zero_matrix = z
         return z.__copy__()
     
@@ -1053 +1050 @@
             [1 3]
             [2 4]
         """
+        if x is 0 or x is None:
+            return self.__matrix_class(self, x, False, False) 
+        
         if isinstance(x, (types.GeneratorType, xrange)):
             x = list(x)
         elif isinstance(x, (int, integer.Integer)) and x==1:

sage/matrix/matrix_window.pxd

@@ -3 +3 @@
 cdef class MatrixWindow:
     cdef Py_ssize_t _row, _col, _nrows, _ncols
     cdef Matrix _matrix
-    cdef object _zero
-
+    cdef object _cached_zero
+    
     # YOU *REALLY SHOULD* OVERRIDE THESE:
     cpdef add(MatrixWindow self, MatrixWindow A)
     cpdef subtract(MatrixWindow self, MatrixWindow A)
@@ -32 +32 @@
                                          Py_ssize_t n_rows, Py_ssize_t n_cols)
     cpdef matrix(MatrixWindow self)
     cpdef swap_rows(MatrixWindow self, Py_ssize_t a, Py_ssize_t b)
-
-
-            
+    cdef object _zero(self)

sage/matrix/matrix_window.pyx

@@ -34 +34 @@
         M._col = col
         M._nrows = n_rows
         M._ncols = n_cols
-        M._zero = self._zero
+        M._cached_zero = self._cached_zero
         return M
 
     def __init__(MatrixWindow self, Matrix matrix,
@@ -44 +44 @@
         self._col = col
         self._nrows = nrows
         self._ncols = ncols
-        self._zero = matrix.base_ring()(0)  # expensive
+    
+    cdef object _zero(self):
+        if self._cached_zero is None:
+            self._cached_zero = self._matrix.base_ring()(0)  # expensive
+        return self._cached_zero
 
     cpdef MatrixWindow matrix_window(MatrixWindow self, Py_ssize_t row, Py_ssize_t col,
                                     Py_ssize_t n_rows, Py_ssize_t n_cols):
@@ -151 +155 @@
                 
     cpdef set_to_zero(MatrixWindow self):
         cdef Py_ssize_t i, j
-        z = self._zero
+        z = self._zero()
         for i from 0 <= i < self._nrows:
             for j from 0 <= j < self._ncols:
                 self.set_unsafe(i, j, z)
@@ -194 +198 @@
             raise ArithmeticError, "incompatible dimensions"
         for i from 0 <= i < A._nrows:
             for j from 0 <= j < B._ncols:
-                s = self._zero
+                s = self._zero()
                 for k from 0 <= k < A._ncols:
                     s = s + A.get_unsafe(i, k) * B.get_unsafe(k, j)
                 self.set_unsafe(i, j, s)
@@ -234 +238 @@
         return echelon.pivots()
         
     cpdef bint element_is_zero(MatrixWindow self, Py_ssize_t i, Py_ssize_t j):
-        return self._matrix.get_unsafe(i+self._row, j+self._col) == self._zero
+        return self._matrix.get_unsafe(i+self._row, j+self._col) == self._zero()