Beispiel #1
0
def projector(ms: xp.ndarray) -> xp.ndarray:
    # projector
    proj = xp.tensordot(ms, ms.conj(), axes=(-1, -1))
    sz = int(np.prod(ms.shape[:-1]))
    Iden = xp.array(xp.diag(xp.ones(sz)), dtype=backend.real_dtype).reshape(proj.shape)
    proj = Iden - proj
    return proj
Beispiel #2
0
 def apply(self, mp, canonicalise=False) -> "MpDmBase":
     # Note usually mp is an mpo
     assert not mp.is_mps
     new_mpdm = self.metacopy()
     if mp.is_complex:
         new_mpdm.to_complex(inplace=True)
     # todo: also duplicate with MPO apply. What to do???
     for i, (mt_self, mt_other) in enumerate(zip(self, mp)):
         assert mt_self.shape[2] == mt_other.shape[1]
         # mt=np.einsum("apqb,cqrd->acprbd",mt_s,mt_o)
         mt = xp.moveaxis(
             xp.tensordot(mt_self.array, mt_other.array, axes=([2], [1])),
             [-3, -2],
             [1, 3],
         )
         mt = mt.reshape((
             mt_self.shape[0] * mt_other.shape[0],
             mt_self.shape[1],
             mt_other.shape[2],
             mt_self.shape[-1] * mt_other.shape[-1],
         ))
         new_mpdm[i] = mt
     qn = mp.dummy_qn
     new_mpdm.qn = [
         np.add.outer(np.array(qn_o), np.array(qn_m)).ravel().tolist()
         for qn_o, qn_m in zip(self.qn, qn)
     ]
     if canonicalise:
         new_mpdm.canonicalise()
     return new_mpdm
Beispiel #3
0
def tensordot(a: Union[Matrix, xp.ndarray], b: Union[Matrix, xp.ndarray], axes):
    matrix_flag = False
    if isinstance(a, Matrix):
        a = a.array
        assert isinstance(b, Matrix)
        b = b.array
        matrix_flag = True
    else:
        assert isinstance(b, xp.ndarray)
    res = xp.tensordot(a, b, axes)
    if matrix_flag:
        return Matrix(res)
    else:
        return res
Beispiel #4
0
    def optimize_cv(self, lr_group, direction, isite, num, percent=0):
        if self.spectratype == "abs":
            # quantum number restriction, |1><0|
            up_exciton, down_exciton = 1, 0
        elif self.spectratype == "emi":
            # quantum number restriction, |0><1|
            up_exciton, down_exciton = 0, 1
        nexciton = 1
        first_LR, second_LR, third_LR, forth_LR = lr_group

        if self.method == "1site":
            add_list = [isite - 1]
            first_L = asxp(first_LR[isite - 1])
            first_R = asxp(first_LR[isite])
            second_L = asxp(second_LR[isite - 1])
            second_R = asxp(second_LR[isite])
            third_L = asxp(third_LR[isite - 1])
            third_R = asxp(third_LR[isite])
            forth_L = asxp(forth_LR[isite - 1])
            forth_R = asxp(forth_LR[isite])
        else:
            add_list = [isite - 2, isite - 1]
            first_L = asxp(first_LR[isite - 2])
            first_R = asxp(first_LR[isite])
            second_L = asxp(second_LR[isite - 2])
            second_R = asxp(second_LR[isite])
            third_L = asxp(third_LR[isite - 2])
            third_R = asxp(third_LR[isite])
            forth_L = asxp(forth_LR[isite - 2])
            forth_R = asxp(forth_LR[isite])

        xqnmat, xqnbigl, xqnbigr, xshape = \
            self.construct_X_qnmat(add_list, direction)
        dag_qnmat, dag_qnbigl, dag_qnbigr = self.swap(xqnmat, xqnbigl, xqnbigr,
                                                      direction)

        nonzeros = np.sum(self.condition(dag_qnmat,
                                         [down_exciton, up_exciton]))

        if self.method == "1site":
            guess = moveaxis(self.cv_mpo[isite - 1], (1, 2), (2, 1))
        else:
            guess = tensordot(moveaxis(self.cv_mpo[isite - 2], (1, 2), (2, 1)),
                              moveaxis(self.cv_mpo[isite - 1]),
                              axes=(-1, 0))
        guess = guess[self.condition(dag_qnmat,
                                     [down_exciton, up_exciton])].reshape(
                                         nonzeros, 1)

        if self.method == "1site":
            # define dot path
            path_1 = [([0, 1], "abc, adef -> bcdef"),
                      ([2, 0], "bcdef, begh -> cdfgh"),
                      ([1, 0], "cdfgh, fhi -> cdgi")]
            path_2 = [([0, 1], "abcd, aefg -> bcdefg"),
                      ([3, 0], "bcdefg, bfhi -> cdeghi"),
                      ([2, 0], "cdeghi, djek -> cghijk"),
                      ([1, 0], "cghijk, gilk -> chjl")]
            path_4 = [([0, 1], "ab, acde -> bcde"), ([1,
                                                      0], "bcde, ef -> bcdf")]

            vecb = multi_tensor_contract(
                path_4, forth_L,
                moveaxis(self.a_ket_mpo[isite - 1], (1, 2), (2, 1)), forth_R)
            vecb = -self.eta * vecb

        a_oper_isite = asxp(self.a_oper[isite - 1])
        b_oper_isite = asxp(self.b_oper[isite - 1])
        h_mpo_isite = asxp(self.h_mpo[isite - 1])
        # construct preconditioner
        Idt = xp.identity(h_mpo_isite.shape[1])
        M1_1 = xp.einsum('aea->ae', first_L)
        M1_2 = xp.einsum('eccf->ecf', a_oper_isite)
        M1_3 = xp.einsum('dfd->df', first_R)
        M1_4 = xp.einsum('bb->b', Idt)
        path_m1 = [([0, 1], "ae,b->aeb"), ([2, 0], "aeb,ecf->abcf"),
                   ([1, 0], "abcf, df->abcd")]
        pre_M1 = multi_tensor_contract(path_m1, M1_1, M1_4, M1_2, M1_3)
        pre_M1 = pre_M1[self.condition(dag_qnmat, [down_exciton, up_exciton])]

        M2_1 = xp.einsum('aeag->aeg', second_L)
        M2_2 = xp.einsum('eccf->ecf', b_oper_isite)
        M2_3 = xp.einsum('gbbh->gbh', h_mpo_isite)
        M2_4 = xp.einsum('dfdh->dfh', second_R)
        path_m2 = [([0, 1], "aeg,gbh->aebh"), ([2, 0], "aebh,ecf->abchf"),
                   ([1, 0], "abhcf,dfh->abcd")]
        pre_M2 = multi_tensor_contract(path_m2, M2_1, M2_3, M2_2, M2_4)
        pre_M2 = pre_M2[self.condition(dag_qnmat, [down_exciton, up_exciton])]

        M4_1 = xp.einsum('faah->fah', third_L)
        M4_4 = xp.einsum('gddi->gdi', third_R)
        M4_5 = xp.einsum('cc->c', Idt)
        M4_path = [([0, 1], "fah,febg->ahebg"), ([2, 0], "ahebg,hjei->abgji"),
                   ([1, 0], "abgji,gdi->abjd")]
        pre_M4 = multi_tensor_contract(M4_path, M4_1, h_mpo_isite, h_mpo_isite,
                                       M4_4)
        pre_M4 = xp.einsum('abbd->abd', pre_M4)
        pre_M4 = xp.tensordot(pre_M4, M4_5, axes=0)
        pre_M4 = xp.moveaxis(pre_M4, [2, 3], [3, 2])[self.condition(
            dag_qnmat, [down_exciton, up_exciton])]

        pre_M = (pre_M1 + 2 * pre_M2 + pre_M4)

        indices = np.array(range(nonzeros))
        indptr = np.array(range(nonzeros + 1))
        pre_M = scipy.sparse.csc_matrix((asnumpy(pre_M), indices, indptr),
                                        shape=(nonzeros, nonzeros))

        M_x = lambda x: scipy.sparse.linalg.spsolve(pre_M, x)
        M = scipy.sparse.linalg.LinearOperator((nonzeros, nonzeros), M_x)

        count = 0

        def hop(x):
            nonlocal count
            count += 1
            dag_struct = asxp(self.dag2mat(xshape, x, dag_qnmat, direction))
            if self.method == "1site":

                M1 = multi_tensor_contract(path_1, first_L, dag_struct,
                                           a_oper_isite, first_R)
                M2 = multi_tensor_contract(path_2, second_L, dag_struct,
                                           b_oper_isite, h_mpo_isite, second_R)
                M2 = xp.moveaxis(M2, (1, 2), (2, 1))
                M3 = multi_tensor_contract(path_2, third_L, h_mpo_isite,
                                           dag_struct, h_mpo_isite, third_R)
                M3 = xp.moveaxis(M3, (1, 2), (2, 1))
                cout = M1 + 2 * M2 + M3
            cout = cout[self.condition(dag_qnmat,
                                       [down_exciton, up_exciton])].reshape(
                                           nonzeros, 1)
            return asnumpy(cout)

        # Matrix A and Vector b
        vecb = asnumpy(vecb)[self.condition(
            dag_qnmat, [down_exciton, up_exciton])].reshape(nonzeros, 1)
        mata = scipy.sparse.linalg.LinearOperator((nonzeros, nonzeros),
                                                  matvec=hop)

        # conjugate gradient method
        # x, info = scipy.sparse.linalg.cg(MatA, VecB, atol=0)
        if num == 1:
            x, info = scipy.sparse.linalg.cg(mata,
                                             vecb,
                                             tol=1.e-5,
                                             maxiter=500,
                                             M=M,
                                             atol=0)
        else:
            x, info = scipy.sparse.linalg.cg(mata,
                                             vecb,
                                             tol=1.e-5,
                                             x0=guess,
                                             maxiter=500,
                                             M=M,
                                             atol=0)
        # logger.info(f"linear eq dim: {nonzeros}")
        # logger.info(f'times for hop:{count}')
        self.hop_time.append(count)
        if info != 0:
            logger.warning(
                f"cg not converged, vecb.norm:{np.linalg.norm(vecb)}")
        l_value = np.inner(
            hop(x).reshape(1, nonzeros), x.reshape(1, nonzeros)) - \
            2 * np.inner(vecb.reshape(1, nonzeros), x.reshape(1, nonzeros))

        x = self.dag2mat(xshape, x, dag_qnmat, direction)
        if self.method == "1site":
            x = np.moveaxis(x, [1, 2], [2, 1])
        x, xdim, xqn, compx = self.x_svd(x,
                                         xqnbigl,
                                         xqnbigr,
                                         nexciton,
                                         direction,
                                         percent=percent)

        if self.method == "1site":
            self.cv_mpo[isite - 1] = x
            if direction == "left":
                if isite != 1:
                    self.cv_mpo[isite - 2] = \
                        tensordot(self.cv_mpo[isite - 2], compx, axes=(-1, 0))
                    self.cv_mpo.qn[isite - 1] = xqn
                else:
                    self.cv_mpo[isite - 1] = \
                        tensordot(compx, self.cv_mpo[isite - 1], axes=(-1, 0))
            elif direction == "right":
                if isite != len(self.cv_mpo):
                    self.cv_mpo[isite] = \
                        tensordot(compx, self.cv_mpo[isite], axes=(-1, 0))
                    self.cv_mpo.qn[isite] = xqn
                else:
                    self.cv_mpo[isite - 1] = \
                        tensordot(self.cv_mpo[isite - 1], compx, axes=(-1, 0))

        else:
            if direction == "left":
                self.cv_mpo[isite - 2] = compx
                self.cv_mpo[isite - 1] = x
            else:
                self.cv_mpo[isite - 2] = x
                self.cv_mpo[isite - 1] = compx
            self.cv_mpo.qn[isite - 1] = xqn

        return l_value[0][0]
Beispiel #5
0
def tensordot(a: Union[Matrix, np.ndarray],
              b: Union[Matrix, np.ndarray, xp.ndarray], axes) -> xp.ndarray:
    return xp.tensordot(asxp(a), asxp(b), axes)
Beispiel #6
0
    def optimize_cv(self, lr_group, isite, percent=0.0):
        # depending on the spectratype, to restrict the exction
        first_LR = lr_group[0]
        second_LR = lr_group[1]
        constrain_qn = self.cv_mps.qntot
        # this function aims at solving the work equation of ZT CV-DMRG
        # L = <CV|op_a|CV>+2\eta<op_b|CV>, take a derivative to local CV
        # S-a-S-e-S                          S-a-S-d-S
        # |   d   |                          |   |   |
        # O-b-O-g-O  * CV[isite-1]  = -\eta  |   c   |
        # |   f   |                          |   |   |
        # S-c- -h-S                          S-b- -e-S

        # note to be a_mat * x = vec_b
        # the environment matrix

        if self.method == "1site":
            cidx = [isite - 1]
            first_L = asxp(first_LR[isite - 1])
            first_R = asxp(first_LR[isite])
            second_L = asxp(second_LR[isite - 1])
            second_R = asxp(second_LR[isite])
        else:
            cidx = [isite - 2, isite - 1]
            first_L = asxp(first_LR[isite - 2])
            first_R = asxp(first_LR[isite])
            second_L = asxp(second_LR[isite - 2])
            second_R = asxp(second_LR[isite])

        # this part just be similar with ground state calculation
        qnbigl, qnbigr, qnmat = self.cv_mps._get_big_qn(cidx)
        xshape = qnmat.shape
        nonzeros = int(np.sum(qnmat == constrain_qn))
        if self.method == '1site':
            guess = self.cv_mps[isite - 1][qnmat == constrain_qn]
            path_b = [([0, 1], "ab, acd->bcd"),
                      ([1, 0], "bcd, de->bce")]
            vec_b = multi_tensor_contract(
                path_b, second_L, self.b_mps[isite - 1], second_R
            )[qnmat == constrain_qn]
        else:
            guess = tensordot(
                self.cv_mps[isite - 2], self.cv_mps[isite - 1], axes=(-1, 0)
            )[qnmat == constrain_qn]
            path_b = [([0, 1], "ab, acd->bcd"),
                      ([2, 0], "bcd, def->bcef"),
                      ([1, 0], "bcef, fg->bceg")]
            vec_b = multi_tensor_contract(
                path_b, second_L, self.b_mps[isite - 2],
                self.b_mps[isite - 1], second_R
            )[qnmat == constrain_qn]

        if self.method == "2site":
            a_oper_isite2 = asxp(self.a_oper[isite - 2])
        else:
            a_oper_isite2 = None
        a_oper_isite1 = asxp(self.a_oper[isite - 1])

        # use the diagonal part of mat_a to construct the preconditinoner
        # for linear solver
        part_l = xp.einsum('abca->abc', first_L)
        part_r = xp.einsum('hfgh->hfg', first_R)
        if self.method == "1site":
            #  S-a   d    h-S
            #  O-b  -O-   f-O
            #  |     e      |
            #  O-c  -O-   g-O
            #  S-a   i    h-S
            path_pre = [([0, 1], "abc, bdef -> acdef"),
                        ([1, 0], "acdef, ceig -> adfig")]
            a_diag = multi_tensor_contract(path_pre, part_l, a_oper_isite1,
                                           a_oper_isite1)
            a_diag = xp.einsum("adfdg -> adfg", a_diag)
            a_diag = xp.tensordot(a_diag, part_r,
                                  axes=([2, 3], [1, 2]))[qnmat == constrain_qn]
        else:
            #  S-a   d     k   h-S
            #  O-b  -O- j -O-  f-O
            #  |     e     l   |
            #  O-c  -O- m -O-  g-O
            #  S-a   i     n   h-S
            # first left half, second right half, last contraction

            path_pre = [([0, 1], "abc, bdej -> acdej"),
                        ([1, 0], "acdej, ceim -> adjim")]
            a_diagl = multi_tensor_contract(path_pre, part_l, a_oper_isite2,
                                            a_oper_isite2)
            a_diagl = xp.einsum("adjdm -> adjm", a_diagl)

            path_pre = [([0, 1], "hfg, jklf -> hgjkl"),
                        ([1, 0], "hgjkl, mlng -> hjkmn")]
            a_diagr = multi_tensor_contract(path_pre, part_r, a_oper_isite1,
                                            a_oper_isite1)
            a_diagr = xp.einsum("hjkmk -> khjm", a_diagr)

            a_diag = xp.tensordot(
                a_diagl, a_diagr, axes=([2, 3], [2, 3]))[qnmat == constrain_qn]

        a_diag = asnumpy(a_diag + xp.ones(nonzeros) * self.eta**2)
        M_x = lambda x: x / a_diag
        pre_M = scipy.sparse.linalg.LinearOperator((nonzeros, nonzeros), M_x)

        count = 0

        # cache oe path
        if self.method == "2site":
            expr = oe.contract_expression(
                "abcd, befh, cfgi, hjkn, iklo, mnop, dglp -> aejm",
                first_L, a_oper_isite2, a_oper_isite2, a_oper_isite1,
                a_oper_isite1, first_R, xshape,
                constants=[0, 1, 2, 3, 4, 5])

        def hop(c):
            nonlocal count
            count += 1
            xstruct = asxp(cvec2cmat(xshape, c, qnmat, constrain_qn))
            if self.method == "1site":
                path_a = [([0, 1], "abcd, aef->bcdef"),
                          ([3, 0], "bcdef, begh->cdfgh"),
                          ([2, 0], "cdfgh, cgij->dfhij"),
                          ([1, 0], "dfhij, fhjk->dik")]
                ax1 = multi_tensor_contract(path_a, first_L, xstruct,
                                            a_oper_isite1, a_oper_isite1, first_R)
            else:
                # opt_einsum v3.2.1 is not bad, ~10% faster than the hand-design
                # contraction path for this complicated cases and consumes a little bit less memory
                # this is the only place in renormalizer we use opt_einsum now.
                # we keep it here just for a demo.
                # ax1 = oe.contract("abcd, befh, cfgi, hjkn, iklo, mnop, dglp -> aejm",
                #        first_L, a_oper_isite2, a_oper_isite2, a_oper_isite1,
                #        a_oper_isite1, first_R, xstruct)
                if USE_GPU:
                    oe_backend = "cupy"
                else:
                    oe_backend = "numpy"
                ax1 = expr(xstruct, backend=oe_backend)   
                #print(oe.contract_path("abcd, befh, cfgi, hjkn, iklo, mnop, dglp -> aejm",
                #        first_L, a_oper_isite2, a_oper_isite2, a_oper_isite1,
                #        a_oper_isite1, first_R, xstruct))

                #path_a = [([0, 1], "abcd, aefg->bcdefg"),
                #          ([5, 0], "bcdefg, behi->cdfghi"),
                #          ([4, 0], "cdfghi, ifjk->cdghjk"),
                #          ([3, 0], "cdghjk, chlm->dgjklm"),
                #          ([2, 0], "dgjklm, mjno->dgklno"),
                #          ([1, 0], "dgklno, gkop->dlnp")]
                #ax1 = multi_tensor_contract(path_a, first_L, xstruct,
                #                           a_oper_isite2, a_oper_isite1,
                #                           a_oper_isite2, a_oper_isite1,
                #                           first_R)
            ax = ax1 + xstruct * self.eta**2
            cout = ax[qnmat == constrain_qn]
            return asnumpy(cout)

        mat_a = scipy.sparse.linalg.LinearOperator((nonzeros, nonzeros),
                                                   matvec=hop)

        x, info = scipy.sparse.linalg.cg(mat_a, asnumpy(vec_b), tol=1.e-5,
                                         x0=asnumpy(guess),
                                         M=pre_M, atol=0)

        self.hop_time.append(count)
        if info != 0:
            logger.info(f"iteration solver not converged")
        # the value of the functional L
        l_value = xp.dot(asxp(hop(x)), asxp(x)) - 2 * xp.dot(vec_b, asxp(x))
        xstruct = cvec2cmat(xshape, x, qnmat, constrain_qn)
        self.cv_mps._update_mps(xstruct, cidx, qnbigl, qnbigr, self.m_max, percent)
        
        return float(l_value)
Beispiel #7
0
    def optimize_cv(self, lr_group, isite, percent=0):
        if self.spectratype == "abs":
            # quantum number restriction, |1><0|
            up_exciton, down_exciton = 1, 0
        elif self.spectratype == "emi":
            # quantum number restriction, |0><1|
            up_exciton, down_exciton = 0, 1
        nexciton = 1
        first_LR, second_LR, third_LR, forth_LR = lr_group

        if self.method == "1site":
            add_list = [isite - 1]
            first_L = asxp(first_LR[isite - 1])
            first_R = asxp(first_LR[isite])
            second_L = asxp(second_LR[isite - 1])
            second_R = asxp(second_LR[isite])
            third_L = asxp(third_LR[isite - 1])
            third_R = asxp(third_LR[isite])
            forth_L = asxp(forth_LR[isite - 1])
            forth_R = asxp(forth_LR[isite])
        else:
            add_list = [isite - 2, isite - 1]
            first_L = asxp(first_LR[isite - 2])
            first_R = asxp(first_LR[isite])
            second_L = asxp(second_LR[isite - 2])
            second_R = asxp(second_LR[isite])
            third_L = asxp(third_LR[isite - 2])
            third_R = asxp(third_LR[isite])
            forth_L = asxp(forth_LR[isite - 2])
            forth_R = asxp(forth_LR[isite])

        xqnmat, xqnbigl, xqnbigr, xshape = \
            self.construct_X_qnmat(add_list)
        dag_qnmat, dag_qnbigl, dag_qnbigr = self.swap(xqnmat, xqnbigl, xqnbigr)
        nonzeros = int(
            np.sum(self.condition(dag_qnmat, [down_exciton, up_exciton])))

        if self.method == "1site":
            guess = moveaxis(self.cv_mpo[isite - 1], (1, 2), (2, 1))
        else:
            guess = tensordot(moveaxis(self.cv_mpo[isite - 2], (1, 2), (2, 1)),
                              moveaxis(self.cv_mpo[isite - 1]),
                              axes=(-1, 0))
        guess = guess[self.condition(dag_qnmat, [down_exciton, up_exciton])]

        if self.method == "1site":
            # define dot path
            path_1 = [([0, 1], "abcd, aefg -> bcdefg"),
                      ([3, 0], "bcdefg, bfhi -> cdeghi"),
                      ([2, 0], "cdeghi, chjk -> degijk"),
                      ([1, 0], "degijk, gikl -> dejl")]
            path_2 = [([0, 1], "abcd, aefg -> bcdefg"),
                      ([3, 0], "bcdefg, bfhi -> cdeghi"),
                      ([2, 0], "cdeghi, djek -> cghijk"),
                      ([1, 0], "cghijk, gilk -> chjl")]
            path_3 = [([0, 1], "ab, acde -> bcde"), ([1,
                                                      0], "bcde, ef -> bcdf")]

            vecb = multi_tensor_contract(
                path_3, forth_L, moveaxis(self.b_mpo[isite - 1], (1, 2),
                                          (2, 1)),
                forth_R)[self.condition(dag_qnmat, [down_exciton, up_exciton])]

        a_oper_isite = asxp(self.a_oper[isite - 1])
        h_mpo_isite = asxp(self.h_mpo[isite - 1])
        # construct preconditioner
        Idt = xp.identity(h_mpo_isite.shape[1])
        M1_1 = xp.einsum('abca->abc', first_L)
        path_m1 = [([0, 1], "abc, bdef->acdef"), ([1,
                                                   0], "acdef, cegh->adfgh")]
        M1_2 = multi_tensor_contract(path_m1, M1_1, a_oper_isite, a_oper_isite)
        M1_2 = xp.einsum("abcbd->abcd", M1_2)
        M1_3 = xp.einsum('ecde->ecd', first_R)
        M1_4 = xp.einsum('ff->f', Idt)
        path_m1 = [([0, 1], "abcd,ecd->abe"), ([1, 0], "abe,f->abef")]
        pre_M1 = multi_tensor_contract(path_m1, M1_2, M1_3, M1_4)
        pre_M1 = xp.moveaxis(pre_M1, [-2, -1], [-1, -2])[self.condition(
            dag_qnmat, [down_exciton, up_exciton])]

        M2_1 = xp.einsum('aeag->aeg', second_L)
        M2_2 = xp.einsum('eccf->ecf', a_oper_isite)
        M2_3 = xp.einsum('gbbh->gbh', h_mpo_isite)
        M2_4 = xp.einsum('dfdh->dfh', second_R)
        path_m2 = [([0, 1], "aeg,gbh->aebh"), ([2, 0], "aebh,ecf->abchf"),
                   ([1, 0], "abhcf,dfh->abcd")]
        pre_M2 = multi_tensor_contract(path_m2, M2_1, M2_3, M2_2, M2_4)
        pre_M2 = pre_M2[self.condition(dag_qnmat, [down_exciton, up_exciton])]

        M4_1 = xp.einsum('faah->fah', third_L)
        M4_4 = xp.einsum('gddi->gdi', third_R)
        M4_5 = xp.einsum('cc->c', Idt)
        M4_path = [([0, 1], "fah,febg->ahebg"), ([2, 0], "ahebg,hjei->abgji"),
                   ([1, 0], "abgji,gdi->abjd")]
        pre_M4 = multi_tensor_contract(M4_path, M4_1, h_mpo_isite, h_mpo_isite,
                                       M4_4)
        pre_M4 = xp.einsum('abbd->abd', pre_M4)
        pre_M4 = xp.tensordot(pre_M4, M4_5, axes=0)
        pre_M4 = xp.moveaxis(pre_M4, [2, 3], [3, 2])[self.condition(
            dag_qnmat, [down_exciton, up_exciton])]

        M_x = lambda x: asnumpy(
            asxp(x) /
            (pre_M1 + 2 * pre_M2 + pre_M4 + xp.ones(nonzeros) * self.eta**2))
        pre_M = scipy.sparse.linalg.LinearOperator((nonzeros, nonzeros), M_x)

        count = 0

        def hop(x):
            nonlocal count
            count += 1
            dag_struct = asxp(self.dag2mat(xshape, x, dag_qnmat))
            if self.method == "1site":

                M1 = multi_tensor_contract(path_1, first_L, dag_struct,
                                           a_oper_isite, a_oper_isite, first_R)
                M2 = multi_tensor_contract(path_2, second_L, dag_struct,
                                           a_oper_isite, h_mpo_isite, second_R)
                M2 = xp.moveaxis(M2, (1, 2), (2, 1))
                M3 = multi_tensor_contract(path_2, third_L, h_mpo_isite,
                                           dag_struct, h_mpo_isite, third_R)
                M3 = xp.moveaxis(M3, (1, 2), (2, 1))
                cout = M1 + 2 * M2 + M3 + dag_struct * self.eta**2
            cout = cout[self.condition(dag_qnmat, [down_exciton, up_exciton])]
            return asnumpy(cout)

        # Matrix A
        mat_a = scipy.sparse.linalg.LinearOperator((nonzeros, nonzeros),
                                                   matvec=hop)

        x, info = scipy.sparse.linalg.cg(mat_a,
                                         asnumpy(vecb),
                                         tol=1.e-5,
                                         x0=asnumpy(guess),
                                         maxiter=500,
                                         M=pre_M,
                                         atol=0)
        # logger.info(f"linear eq dim: {nonzeros}")
        # logger.info(f'times for hop:{count}')
        self.hop_time.append(count)
        if info != 0:
            logger.warning(
                f"cg not converged, vecb.norm:{xp.linalg.norm(vecb)}")
        l_value = xp.dot(asxp(hop(x)), asxp(x)) - 2 * xp.dot(vecb, asxp(x))

        x = self.dag2mat(xshape, x, dag_qnmat)
        if self.method == "1site":
            x = np.moveaxis(x, [1, 2], [2, 1])
        x, xdim, xqn, compx = self.x_svd(x,
                                         xqnbigl,
                                         xqnbigr,
                                         nexciton,
                                         percent=percent)

        if self.method == "1site":
            self.cv_mpo[isite - 1] = x
            if not self.cv_mpo.to_right:
                if isite != 1:
                    self.cv_mpo[isite - 2] = \
                        tensordot(self.cv_mpo[isite - 2], compx, axes=(-1, 0))
                    self.cv_mpo.qn[isite - 1] = xqn
                    self.cv_mpo.qnidx = isite - 2
                else:
                    self.cv_mpo[isite - 1] = \
                        tensordot(compx, self.cv_mpo[isite - 1], axes=(-1, 0))
                    self.cv_mpo.qnidx = 0
            else:
                if isite != len(self.cv_mpo):
                    self.cv_mpo[isite] = \
                        tensordot(compx, self.cv_mpo[isite], axes=(-1, 0))
                    self.cv_mpo.qn[isite] = xqn
                    self.cv_mpo.qnidx = isite
                else:
                    self.cv_mpo[isite - 1] = \
                        tensordot(self.cv_mpo[isite - 1], compx, axes=(-1, 0))
                    self.cv_mpo.qnidx = self.cv_mpo.site_num - 1

        else:
            if not self.cv_mpo.to_right:
                self.cv_mpo[isite - 2] = compx
                self.cv_mpo[isite - 1] = x
                self.cv_mpo.qnidx = isite - 2
            else:
                self.cv_mpo[isite - 2] = x
                self.cv_mpo[isite - 1] = compx
                self.cv_mpo.qnidx = isite - 1
            self.cv_mpo.qn[isite - 1] = xqn

        return float(l_value)