def solve(self, B): # modified Algorithm 2.3.4 of Cohen's book
"""
Return solution X for self * X = B (B is a vector).
This function returns tuple (V, M) below.
V: one solution as vector
M: kernel of self as list of basis vectors.
If you want only one solution, use 'inverseImage'.
Warning: B should not be a matrix instead of a vector
"""
M_1 = self.copy()
M_1.insertColumn(self.column + 1, B.compo)
M_1._cohensSimplify = types.MethodType(parallel_cohens, M_1)
V = M_1.kernel()
ker = []
flag = False
if not V:
raise NoInverseImage("no solution")
n = V.row
for j in range(1, V.column + 1):
if not bool(V[n, j]): # self's kernel
ker.append(vector.Vector([V[i, j] for i in range(1, n)]))
elif not (flag):
d = -ring.inverse(V[n, j])
sol = vector.Vector([V[i, j] * d for i in range(1, n)])
flag = True
if not (flag):
raise NoInverseImage("no solution")
return sol, ker
def parallel_cohens(self):
"""
NS: Add some parallel processing to the cohensSimplify procedure
_cohensSimplify is a common process used in image() and kernel()
Return a tuple of modified matrix M, image data c and kernel data d.
"""
print >>sys.stderr, "Parallel Cohens simplify %dx%d" % (self.row, self.column)
M = self.copy()
c = [0] * (M.row + 1)
d = [-1] * (M.column + 1)
Mpr = [pack_vector(M.getRow(i)) for i in range1(M.row)]
for k in range(1, M.column + 1):
for j in range(1, M.row + 1):
if not c[j] and Mpr[j - 1][0][k - 1]:
break
else: # not found j such that m(j, k)!=0 and c[j]==0
d[k] = 0
continue
Mj = unpack_vector(Mpr[j - 1])
top = -ring.inverse(Mj[k])
Mj[k] = -self.coeff_ring.one
for s in range(k + 1, M.column + 1):
Mj[s] = top * Mj[s]
Mjp = pack_vector(Mj)
Mpr[j - 1] = Mjp
work = [(Mpr[i - 1], Mjp, k) for i in range(1, M.row + 1) if i != j]
result = pool.pool().map(cohens_worker, work)
i = 1
for v in result:
if i != j:
Mpr[i - 1] = v
else:
i += 1
Mpr[i - 1] = v
i += 1
c[j] = k
d[k] = j
for i in range(1, M.row + 1):
M.setRow(i, unpack_vector(Mpr[i - 1]))
return (M, c, d)
def reduce_groebner(gbasis, order):
"""
Return the reduced Groebner basis constructed from a Groebner
basis.
1) lb(f) divides lb(g) => g is not in reduced Groebner basis
2) monic
"""
reduced_basis = []
lb_rel = dict([(order.leading_term(g)[0], g) for g in gbasis])
lbs = sorted([order.leading_term(g)[0] for g in gbasis])[::-1]
for i, lbi in enumerate(lbs):
for lbj in lbs[(len(lbs) - 1) : i : -1]:
if lbi == lbj.lcm(lbi):
# divisor found
break
else:
g = lb_rel[lbi]
if g[lbi] != ring.getRing(g[lbi]).one:
# make it monic
g = g.scalar_mul(ring.inverse(g[lbi]))
reduced_basis.append(g)
return reduced_basis
def reduce_groebner(gbasis, order):
"""
Return the reduced Groebner basis constructed from a Groebner
basis.
1) lb(f) divides lb(g) => g is not in reduced Groebner basis
2) monic
"""
reduced_basis = []
lb_rel = dict([(order.leading_term(g)[0], g) for g in gbasis])
lbs = sorted([order.leading_term(g)[0] for g in gbasis])[::-1]
for i, lbi in enumerate(lbs):
for lbj in lbs[(len(lbs) - 1):i:-1]:
if lbi == lbj.lcm(lbi):
# divisor found
break
else:
g = lb_rel[lbi]
if g[lbi] != ring.getRing(g[lbi]).one:
# make it monic
g = g.scalar_mul(ring.inverse(g[lbi]))
reduced_basis.append(g)
return reduced_basis
def testRational(self):
self.assertEqual(rational.Rational(3, 2),
ring.inverse(rational.Rational(2, 3)))
def testComplex(self):
self.assertEqual(-1j, ring.inverse(1j))
def testFloat(self):
self.assertEqual(0.5, ring.inverse(2.0))
def testInt(self):
self.assertEqual(rational.Rational(1, 2), ring.inverse(2))
