def initialize(self,num_reals=1,enforce_bounds="reset",
                   parensemble=None,obsensemble=None,restart_obsensemble=None):
        """Initialize.  Depending on arguments, draws or loads
        initial parameter observations ensembles and runs the initial parameter
        ensemble

        Parameters
        ----------
            num_reals : int
                the number of realizations to draw.  Ignored if parensemble/obsensemble
                are not None
            enforce_bounds : str
                how to enfore parameter bound transgression.  options are
                reset, drop, or None
            parensemble : pyemu.ParameterEnsemble or str
                a parameter ensemble or filename to use as the initial
                parameter ensemble.  If not None, then obsenemble must not be
                None
            obsensemble : pyemu.ObservationEnsemble or str
                an observation ensemble or filename to use as the initial
                observation ensemble.  If not None, then parensemble must
                not be None
            restart_obsensemble : pyemu.ObservationEnsemble or str
                an observation ensemble or filename to use as an
                evaluated observation ensemble.  If not None, this will skip the initial
                parameter ensemble evaluation - user beware!

        """

        build_empirical_prior = False

        # initialize the phi report csv
        self.enforce_bounds = enforce_bounds

        self.total_runs = 0
        # this matrix gets used a lot, so only calc once and store
        self.obscov_inv_sqrt = self.obscov.get(self.pst.nnz_obs_names).inv.sqrt

        self.logger.log("forming inverse sqrt parcov matrix")
        self.parcov_inv_sqrt = self.parcov.inv.sqrt
        self.logger.log("forming inverse sqrt parcov matrix")

        if parensemble is not None and obsensemble is not None:
            self.logger.log("initializing with existing ensembles")
            if isinstance(parensemble,str):
                self.logger.log("loading parensemble from file")
                if not os.path.exists(obsensemble):
                    self.logger.lraise("can not find parensemble file: {0}".\
                                       format(parensemble))
                df = pd.read_csv(parensemble,index_col=0)
                df.columns = df.columns.str.lower()
                #df.index = [str(i) for i in df.index]
                self.parensemble_0 = pyemu.ParameterEnsemble.from_dataframe(df=df,pst=self.pst)
                self.logger.log("loading parensemble from file")

            elif isinstance(parensemble,ParameterEnsemble):
                self.parensemble_0 = parensemble.copy()
            else:
                raise Exception("unrecognized arg type for parensemble, " +\
                                "should be filename or ParameterEnsemble" +\
                                ", not {0}".format(type(parensemble)))
            self.parensemble = self.parensemble_0.copy()
            if isinstance(obsensemble,str):
                self.logger.log("loading obsensemble from file")
                if not os.path.exists(obsensemble):
                    self.logger.lraise("can not find obsensemble file: {0}".\
                                       format(obsensemble))
                df = pd.read_csv(obsensemble,index_col=0)
                df.columns = df.columns.str.lower()
                df = df.loc[:,self.pst.nnz_obs_names]
                #df.index = [str(i) for i in df.index]
                self.obsensemble_0 = pyemu.ObservationEnsemble.from_dataframe(df=df,pst=self.pst)
                self.logger.log("loading obsensemble from file")

            elif isinstance(obsensemble,ObservationEnsemble):
                self.obsensemble_0 = obsensemble.copy()
            else:
                raise Exception("unrecognized arg type for obsensemble, " +\
                                "should be filename or ObservationEnsemble" +\
                                ", not {0}".format(type(obsensemble)))

            assert self.parensemble_0.shape[0] == self.obsensemble_0.shape[0]
            #self.num_reals = self.parensemble_0.shape[0]
            num_reals = self.parensemble.shape[0]
            self.logger.log("initializing with existing ensembles")

            if build_empirical_prior:

                self.reset_parcov(self.parensemble.covariance_matrix())
                if self.save_mats:
                    self.parcov.to_binary(self.pst.filename+".empcov.jcb")

        else:
            if build_empirical_prior:
                self.logger.lraise("can't use build_emprirical_prior without parensemble...")
            self.logger.log("initializing with {0} realizations".format(num_reals))
            self.logger.log("initializing parensemble")
            self.parensemble_0 = pyemu.ParameterEnsemble.from_gaussian_draw(self.pst,
                                                                            self.parcov,num_reals=num_reals)
            self.parensemble_0.enforce(enforce_bounds=enforce_bounds)
            self.logger.log("initializing parensemble")
            self.parensemble = self.parensemble_0.copy()
            self.parensemble_0.to_csv(self.pst.filename +\
                                      self.paren_prefix.format(0))
            self.logger.log("initializing parensemble")
            self.logger.log("initializing obsensemble")
            self.obsensemble_0 = pyemu.ObservationEnsemble.from_id_gaussian_draw(self.pst,
                                                                                 num_reals=num_reals)
            #self.obsensemble = self.obsensemble_0.copy()

            # save the base obsensemble
            self.obsensemble_0.to_csv(self.pst.filename +\
                                      self.obsen_prefix.format(-1))
            self.logger.log("initializing obsensemble")
            self.logger.log("initializing with {0} realizations".format(num_reals))


        self.enforce_bounds = enforce_bounds

        if restart_obsensemble is not None:
            self.logger.log("loading restart_obsensemble {0}".format(restart_obsensemble))
            #failed_runs,self.obsensemble = self._load_obs_ensemble(restart_obsensemble)
            df = pd.read_csv(restart_obsensemble, index_col=0)
            df.columns = df.columns.str.lower()
            #df = df.loc[:, self.pst.nnz_obs_names]
            # df.index = [str(i) for i in df.index]
            self.obsensemble = pyemu.ObservationEnsemble.from_dataframe(df=df, pst=self.pst)
            assert self.obsensemble.shape[0] == self.obsensemble_0.shape[0]
            assert list(self.obsensemble.columns) == list(self.obsensemble_0.columns)
            self.logger.log("loading restart_obsensemble {0}".format(restart_obsensemble))

        else:
            # run the initial parameter ensemble
            self.logger.log("evaluating initial ensembles")
            self.obsensemble = self.forecast()
            self.logger.log("evaluating initial ensembles")

        #if not self.parensemble.istransformed:
        self.parensemble._transform(inplace=True)
        #if not self.parensemble_0.istransformed:
        self.parensemble_0._transform(inplace=True)
        self._initialized = True
Initialize.  Depending on arguments, draws or loads
        initial parameter observations ensembles and runs the initial parameter
        ensemble

        Parameters
        ----------
            num_reals : int
                the number of realizations to draw.  Ignored if parensemble/obsensemble
                are not None
            enforce_bounds : str
                how to enfore parameter bound transgression.  options are
                reset, drop, or None
            parensemble : pyemu.ParameterEnsemble or str
                a parameter ensemble or filename to use as the initial
                parameter ensemble.  If not None, then obsenemble must not be
                None
            obsensemble : pyemu.ObservationEnsemble or str
                an observation ensemble or filename to use as the initial
                observation ensemble.  If not None, then parensemble must
                not be None
            restart_obsensemble : pyemu.ObservationEnsemble or str
                an observation ensemble or filename to use as an
                evaluated observation ensemble.  If not None, this will skip the initial
                parameter ensemble evaluation - user beware!