class DMRGEngine(object): ''' dmrg engine construct:DMRGEngine(lhgen,rhgen) attributes: lhgen:left hamiltonian generator rhgen:right hamiltonian generator N:length of whole chain lblocks:a list to store left generators rblocks:a list to store right generators sblock:super block ''' def __init__(self,lhgen,rhgen): self.lhgen=lhgen self.rhgen=rhgen self.L=self.rhgen.L self.lblocks=[deepcopy(self.lhgen)] self.rblocks=[deepcopy(self.rhgen)] self.d=self.lhgen.d def single_step(self,m): #only for infinite '''single dmrg step.m:number of kept states''' self.lhgen.enlarge() self.rhgen.enlarge() self.sblock=SuperBlock(self.lhgen,self.rhgen,joint=True) E,psi=self.sblock.eigen() print '*'*(self.lhgen.l-1)+'++'+'*'*(self.rhgen.l-1) print 'E=',float(E)/self.sblock.L U=self.sblock.transmat(m);self.lhgen.U=U self.lhgen.transform(U) V=self.sblock.rtransmat(m);self.rhgen.V=V self.rhgen.transform(V) self.lhgen.basis_sector_array=self.sblock.new_sector_array self.lhgen.basis_by_sector=self.sblock.new_basis_by_sector self.rhgen.basis_sector_array=self.sblock.rnew_sector_array self.rhgen.basis_by_sector=self.sblock.rnew_basis_by_sector self.lblocks.append(deepcopy(self.lhgen)) self.rblocks.append(deepcopy(self.rhgen)) def infinite(self,m): '''infinite algorithm''' for i in range(self.L/2-1): self.single_step(m) def right_sweep(self,m): '''sweep one site towards right''' self.rblocks.pop(-1) psi0_guess=np.reshape(self.sblock.full_psi0,(self.lblocks[-2].D*self.d,-1)) psi0_guess=self.lblocks[-1].U.conjugate().transpose().todense().dot(psi0_guess) psi0_guess=psi0_guess.reshape(-1,self.rblocks[-1].D) psi0_guess=psi0_guess.dot(self.rblocks[-1].V.conjugate().transpose().todense()) psi0_guess=psi0_guess.reshape(-1,1) self.rblocks.pop(-1) self.lhgen=deepcopy(self.lblocks[-1]) self.rhgen=deepcopy(self.rblocks[-1]) self.lhgen.enlarge();self.rhgen.enlarge() self.sblock=SuperBlock(self.lhgen,self.rhgen) E,psi=self.sblock.eigen(psi0_guess) print '-'*(self.lblocks[-1].l)+'++'+'='*(self.rblocks[-1].l) print 'E=',float(E)/self.L U=self.sblock.transmat(m);self.lhgen.U=U V=self.sblock.rtransmat(m);self.rhgen.V=V self.lhgen.transform(U) self.rhgen.transform(V) self.lhgen.basis_sector_array=self.sblock.new_sector_array self.lhgen.basis_by_sector=self.sblock.new_basis_by_sector self.rhgen.basis_sector_array=self.sblock.rnew_sector_array self.rhgen.basis_by_sector=self.sblock.rnew_basis_by_sector self.lblocks.append(deepcopy(self.lhgen)) self.rblocks.append(deepcopy(self.rhgen)) def left_sweep(self,m): '''sweep one site towards left''' self.lblocks.pop(-1) psi0_guess=np.reshape(self.sblock.full_psi0,(-1,self.rblocks[-2].D*self.d)) psi0_guess=psi0_guess.dot(self.rblocks[-1].V.todense()) psi0_guess=psi0_guess.reshape(self.lblocks[-1].D,-1) psi0_guess=self.lblocks[-1].U.todense().dot(psi0_guess) psi0_guess=psi0_guess.reshape(-1,1) self.lblocks.pop(-1) self.lhgen=deepcopy(self.lblocks[-1]) self.rhgen=deepcopy(self.rblocks[-1]) self.lhgen.enlarge() self.rhgen.enlarge() self.sblock=SuperBlock(self.lhgen,self.rhgen) E,psi=self.sblock.eigen(psi0_guess) print '='*(self.lblocks[-1].l)+'++'+'-'*(self.rblocks[-1].l) print 'E=',float(E)/self.L U=self.sblock.transmat(m);self.lhgen.U=U V=self.sblock.rtransmat(m);self.rhgen.V=V self.lhgen.transform(U) self.rhgen.transform(V) self.lhgen.basis_sector_array=self.sblock.new_sector_array self.lhgen.basis_by_sector=self.sblock.new_basis_by_sector self.rhgen.basis_sector_array=self.sblock.rnew_sector_array self.rhgen.basis_by_sector=self.sblock.rnew_basis_by_sector self.lblocks.append(deepcopy(self.lhgen)) self.rblocks.append(deepcopy(self.rhgen)) def finite(self,mwarmup,mlist): '''finite algorithm''' self.infinite(mwarmup) #mind the initialize problem for m in mlist: for i in range(self.L/2,self.L-2): self.right_sweep(m) for i in range(1,self.L-3): self.left_sweep(m) for i in range(1,self.L/2-1): self.right_sweep(m) def tomps(self): As=[np.array([[1.,0],[0,1.]])] As[0]=As[0].reshape(-1,2,As[0].shape[-1]) Bs=[np.array([[1.,0],[0,1.]])] Bs[0]=Bs[0].reshape(Bs[0].shape[0],2,-1) for lhgen in self.lblocks[1:]: A=copy(lhgen.U) A=A.toarray() A=A.reshape(-1,2,A.shape[-1]) As.append(A) for rhgen in self.rblocks[1:]: B=copy(rhgen.V) B=B.toarray() B=B.conjugate().transpose() B=B.reshape(B.shape[0],2,-1) Bs.append(B) Bs.reverse() S=self.sblock.s return MPS(self.d,self.L,As,Bs,S)
