Use nmod contexts for nmod_mat

Author: oscarbenjamin

src/flint/types/nmod.pyx

@@ -52,6 +52,23 @@ cdef class nmod_ctx:
         nmod_init(&self.mod, m)
         self._is_prime = n_is_prime(m)
 
+    def __eq__(self, other):
+        # XXX: If we could ensure uniqueness of nmod_ctx for given modulus then
+        # we would need to implement __eq__ and __hash__ at all...
+        #
+        # It isn't possible to ensure uniqueness in __new__ like it is in
+        # Python because we can't return an existing object from __new__. What
+        # we could do though is make it so that __init__ raises an error and
+        # use a static method .new() to create new objects.
+        if self is other:
+            return True
+        if not typecheck(other, nmod_ctx):
+            return NotImplemented
+        return self.mod.n == (<nmod_ctx>other).mod.n
+
+    def __repr__(self):
+        return f"nmod_ctx({self.modulus()})"
+
     cdef int any_as_nmod(self, mp_limb_t * val, obj) except -1:
         """Convert an object to an nmod element."""
         cdef int success
@@ -85,7 +102,7 @@ cdef class nmod_ctx:
         17
 
         """
-        return fmpz(self.mod)
+        return fmpz(self.mod.n)
 
     def is_prime(self):
         """Check if the modulus is prime.
@@ -121,10 +138,10 @@ cdef class nmod_ctx:
         return hash(self.mod)
 
     def __eq__(self, other):
-        if not typecheck(other, nmod_ctx):
-            return NotImplemented
+        if typecheck(other, nmod_ctx):
+            return self.mod.n == (<nmod_ctx>other).mod.n
         else:
-            return self.mod == other.mod
+            return NotImplemented
 
     def __str__(self):
         return f"Context for nmod with modulus: {self.modulus()}"
@@ -165,6 +182,7 @@ cdef class nmod(flint_scalar):
             raise TypeError("Invalid context/modulus for nmod: %s" % mod)
         if not ctx.any_as_nmod(&self.val, val):
             raise TypeError("cannot create nmod from object of type %s" % type(val))
+        self.ctx = ctx
 
     def repr(self):
         return "nmod(%s, %s)" % (self.val, self.ctx.mod.n)
@@ -386,14 +404,14 @@ cdef class nmod(flint_scalar):
         cdef nmod r
         cdef mp_limb_t val
         r = nmod.__new__(nmod)
-        r.mod = self.mod
+        r.ctx = self.ctx
 
         if self.val == 0:
             return r
 
-        val = n_sqrtmod(self.val, self.mod.n)
+        val = n_sqrtmod(self.val, self.ctx.mod.n)
         if val == 0:
-            raise DomainError("no square root exists for %s mod %s" % (self.val, self.mod.n))
+            raise DomainError("no square root exists for %s mod %s" % (self.val, self.ctx.mod.n))
 
         r.val = val
         return r

src/flint/types/nmod_mat.pxd

@@ -3,8 +3,13 @@ from flint.flint_base.flint_base cimport flint_mat
 from flint.flintlib.nmod_mat cimport nmod_mat_t
 from flint.flintlib.flint cimport mp_limb_t
 
+from flint.types.nmod cimport nmod_ctx
+
+
 cdef class nmod_mat(flint_mat):
     cdef nmod_mat_t val
+    cdef nmod_ctx ctx
+
     cpdef long nrows(self)
     cpdef long ncols(self)
     cpdef mp_limb_t modulus(self)

src/flint/types/nmod_mat.pyx

@@ -43,8 +43,7 @@ from flint.flintlib.nmod_mat cimport (
 from flint.utils.typecheck cimport typecheck
 from flint.types.fmpz_mat cimport any_as_fmpz_mat
 from flint.types.fmpz_mat cimport fmpz_mat
-from flint.types.nmod cimport nmod
-from flint.types.nmod cimport any_as_nmod
+from flint.types.nmod cimport nmod, any_as_nmod_ctx
 from flint.types.nmod_poly cimport nmod_poly
 from flint.pyflint cimport global_random_state
 from flint.flint_base.flint_context cimport thectx
@@ -87,20 +86,24 @@ cdef class nmod_mat(flint_mat):
     def __init__(self, *args):
         cdef long m, n, i, j
         cdef mp_limb_t mod
+        cdef nmod_ctx ctx
         if len(args) == 1:
             val = args[0]
             if typecheck(val, nmod_mat):
                 nmod_mat_init_set(self.val, (<nmod_mat>val).val)
+                self.ctx = (<nmod_mat>val).ctx
                 return
         mod = args[-1]
         args = args[:-1]
         if mod == 0:
             raise ValueError("modulus must be nonzero")
+        ctx = any_as_nmod_ctx(mod)
+        self.ctx = ctx
         if len(args) == 1:
             val = args[0]
             if typecheck(val, fmpz_mat):
                 nmod_mat_init(self.val, fmpz_mat_nrows((<fmpz_mat>val).val),
-                    fmpz_mat_ncols((<fmpz_mat>val).val), mod)
+                    fmpz_mat_ncols((<fmpz_mat>val).val), ctx.mod.n)
                 fmpz_mat_get_nmod_mat(self.val, (<fmpz_mat>val).val)
             elif isinstance(val, (list, tuple)):
                 m = len(val)
@@ -112,11 +115,11 @@ cdef class nmod_mat(flint_mat):
                     for i from 1 <= i < m:
                         if len(val[i]) != n:
                             raise ValueError("input rows have different lengths")
-                nmod_mat_init(self.val, m, n, mod)
+                nmod_mat_init(self.val, m, n, ctx.mod.n)
                 for i from 0 <= i < m:
                     row = val[i]
                     for j from 0 <= j < n:
-                        x = nmod(row[j], mod)
+                        x = nmod(row[j], ctx)        # XXX: slow
                         self.val.rows[i][j] = (<nmod>x).val
             else:
                 raise TypeError("cannot create nmod_mat from input of type %s" % type(val))
@@ -131,7 +134,7 @@ cdef class nmod_mat(flint_mat):
                 raise ValueError("list of entries has the wrong length")
             for i from 0 <= i < m:
                 for j from 0 <= j < n:
-                    x = nmod(entries[i*n + j], mod)         # XXX: slow
+                    x = nmod(entries[i*n + j], ctx)         # XXX: slow
                     self.val.rows[i][j] = (<nmod>x).val
         else:
             raise TypeError("nmod_mat: expected 1-3 arguments plus modulus")
@@ -208,7 +211,7 @@ cdef class nmod_mat(flint_mat):
         i, j = index
         if i < 0 or i >= self.nrows() or j < 0 or j >= self.ncols():
             raise IndexError("index %i,%i exceeds matrix dimensions" % (i, j))
-        if any_as_nmod(&v, value, self.val.mod):
+        if self.ctx.any_as_nmod(&v, value):
             nmod_mat_set_entry(self.val, i, j, v)
         else:
             raise TypeError("cannot set item of type %s" % type(value))
@@ -307,7 +310,7 @@ cdef class nmod_mat(flint_mat):
         sv = &(<nmod_mat>s).val[0]
         u = any_as_nmod_mat(t, sv.mod)
         if u is NotImplemented:
-            if any_as_nmod(&c, t, sv.mod):
+            if s.ctx.any_as_nmod(&c, t):
                 return (<nmod_mat>s).__mul_nmod(c)
             return NotImplemented
         tv = &(<nmod_mat>u).val[0]
@@ -324,7 +327,7 @@ cdef class nmod_mat(flint_mat):
         cdef nmod_mat_struct *sv
         cdef mp_limb_t c
         sv = &(<nmod_mat>s).val[0]
-        if any_as_nmod(&c, t, sv.mod):
+        if s.ctx.any_as_nmod(&c, t):
             return (<nmod_mat>s).__mul_nmod(c)
         u = any_as_nmod_mat(t, sv.mod)
         if u is NotImplemented:
@@ -349,7 +352,7 @@ cdef class nmod_mat(flint_mat):
     @staticmethod
     def _div_(nmod_mat s, t):
         cdef mp_limb_t v
-        if not any_as_nmod(&v, t, s.val.mod):
+        if not s.ctx.any_as_nmod(&v, t):
             return NotImplemented
         t = nmod(v, s.val.mod.n)
         return s * (~t)