예제 #1
0
def main(_):
    # setting up output directory
    outdir = os.path.expanduser(FLAGS.outdir)
    #os.makedirs(outdir, exist_ok=True)

    # DATA
    N, M, D, R_true, I_train, I_test = get_data()

    # MODEL
    I = tf.placeholder(tf.float32, [N, M])

    scale_uv = tf.concat(
        [tf.ones([D, N]),
            tf.ones([D, M])], axis=1)
    mean_uv = tf.concat(
        [tf.zeros([D, N]),
            tf.zeros([D, M])], axis=1)

    UV = Normal(loc=mean_uv, scale=scale_uv)
    #R = Normal(
    #    loc=tf.matmul(tf.transpose(UV[:, :N]), UV[:, N:]) * I,
    #    scale=tf.ones([N, M]))
    R = Normal(
        loc=tf.matmul(tf.transpose(UV[:, :N]), UV[:, N:]),
        scale=tf.ones([N, M]))  # generator dist. for matrix
    R_mask = R * I  # generated masked matrix

    sess = tf.InteractiveSession()
    p_joint = Joint(R_true, I_train, sess, D, N, M)

    # INFERENCE
    mean_suv = tf.concat([
        tf.get_variable("qU/loc", [D, N]),
        tf.get_variable("qV/loc", [D, M])
    ],
                            axis=1)
    scale_suv = tf.concat([
        tf.nn.softplus(tf.get_variable("qU/scale", [D, N])),
        tf.nn.softplus(tf.get_variable("qV/scale", [D, M]))
    ],
                            axis=1)

    qUV = Normal(loc=mean_suv, scale=scale_suv)

    inference = ed.KLqp({UV: qUV}, data={R_mask: R_true, I: I_train})
    inference.run(n_iter=FLAGS.VI_iter)

    # CRITICISM
    cR = ed.copy(R_mask, {UV: qUV}) # reconstructed matrix
    test_mse = ed.evaluate('mean_squared_error',
                            data={
                                cR: R_true,
                                I: I_test.astype(bool)
                            })
    logger.info("iters %d ed test mse %.5f" % (FLAGS.VI_iter, test_mse))
    train_mse = ed.evaluate('mean_squared_error',
                            data={
                                cR: R_true,
                                I: I_train.astype(bool)
                            })
    logger.info("iters %d ed train mse %.5f" % (FLAGS.VI_iter, train_mse))

    elbo_t = elbo(qUV, p_joint)
    logger.info('iters %d elbo %.2f' % (FLAGS.VI_iter, elbo_t))
예제 #2
0
def main(_):
    # setting up output directory
    outdir = os.path.expanduser(FLAGS.outdir)
    os.makedirs(outdir, exist_ok=True)

    N, M, D, R_true, I_train, I_test = get_data()
    debug('N, M, D', N, M, D)

    # Solution components
    weights, qUVt_components = [], []

    # Files to log metrics
    times_filename = os.path.join(outdir, 'times.csv')
    mse_train_filename = os.path.join(outdir, 'mse_train.csv')
    mse_test_filename = os.path.join(outdir, 'mse_test.csv')
    ll_test_filename = os.path.join(outdir, 'll_test.csv')
    ll_train_filename = os.path.join(outdir, 'll_train.csv')
    elbos_filename = os.path.join(outdir, 'elbos.csv')
    gap_filename = os.path.join(outdir, 'gap.csv')
    step_filename = os.path.join(outdir, 'steps.csv')
    # 'adafw', 'ada_afw', 'ada_pfw'
    if FLAGS.fw_variant.startswith('ada'):
        lipschitz_filename = os.path.join(outdir, 'lipschitz.csv')
        iter_info_filename = os.path.join(outdir, 'iter_info.txt')

    start = 0
    if FLAGS.restore:
        #start = 50
        #qUVt_components = get_random_components(D, N, M, start)
        #weights = np.random.dirichlet([1.] * start).astype(np.float32)
        #lipschitz_estimate = opt.adafw_linit()
        parameters = np.load(os.path.join(outdir, 'qt_latest.npz'))
        weights = list(parameters['weights'])
        start = parameters['fw_iter']
        qUVt_components = list(parameters['comps'])
        assert len(weights) == len(qUVt_components), "Inconsistent storage"
        # get lipschitz estimate from the file, could've stored it
        # in params but that would mean different saved file for
        # adaptive variants
        if FLAGS.fw_variant.startswith('ada'):
            lipschitz_filename = os.path.join(outdir, 'lipschitz.csv')
            if not os.path.isfile(lipschitz_filename):
                raise ValueError("Inconsistent storage")
            with open(lipschitz_filename, 'r') as f:
                l = f.readlines()
                lipschitz_estimate = float(l[-1].strip())
    else:
        # empty the files present in the folder already
        open(times_filename, 'w').close()
        open(mse_train_filename, 'w').close()
        open(mse_test_filename, 'w').close()
        open(ll_test_filename, 'w').close()
        open(ll_train_filename, 'w').close()
        open(elbos_filename, 'w').close()
        open(gap_filename, 'w').close()
        open(step_filename, 'w').close()
        # 'adafw', 'ada_afw', 'ada_pfw'
        if FLAGS.fw_variant.startswith('ada'):
            open(lipschitz_filename, 'w').close()
            open(iter_info_filename, 'w').close()

    for t in range(start, start + FLAGS.n_fw_iter):
        g = tf.Graph()
        with g.as_default():
            tf.set_random_seed(FLAGS.seed)
            sess = tf.InteractiveSession()
            with sess.as_default():
                # MODEL
                I = tf.placeholder(tf.float32, [N, M])

                scale_uv = tf.concat(
                    [tf.ones([D, N]), tf.ones([D, M])], axis=1)
                mean_uv = tf.concat(
                    [tf.zeros([D, N]), tf.zeros([D, M])], axis=1)

                UV = Normal(loc=mean_uv, scale=scale_uv)
                R = Normal(loc=tf.matmul(tf.transpose(UV[:, :N]), UV[:, N:]),
                           scale=tf.ones([N, M]))  # generator dist. for matrix
                R_mask = R * I  # generated masked matrix

                p_joint = Joint(R_true, I_train, sess, D, N, M)

                if t == 0:
                    fw_iterates = {}
                else:
                    # Current solution
                    prev_components = [
                        coreutils.base_loc_scale('mvn0',
                                                 c['loc'],
                                                 c['scale'],
                                                 multivariate=False)
                        for c in qUVt_components
                    ]
                    qUV_prev = coreutils.get_mixture(weights, prev_components)
                    fw_iterates = {UV: qUV_prev}

                # LMO (via relbo INFERENCE)
                mean_suv = tf.concat([
                    tf.get_variable("qU/loc", [D, N]),
                    tf.get_variable("qV/loc", [D, M])
                ],
                                     axis=1)
                scale_suv = tf.concat([
                    tf.nn.softplus(tf.get_variable("qU/scale", [D, N])),
                    tf.nn.softplus(tf.get_variable("qV/scale", [D, M]))
                ],
                                      axis=1)

                sUV = Normal(loc=mean_suv, scale=scale_suv)

                #inference = relbo.KLqp({UV: sUV}, data={R: R_true, I: I_train},
                inference = relbo.KLqp({UV: sUV},
                                       data={
                                           R_mask: R_true,
                                           I: I_train
                                       },
                                       fw_iterates=fw_iterates,
                                       fw_iter=t)
                inference.run(n_iter=FLAGS.LMO_iter)

                loc_s = sUV.mean().eval()
                scale_s = sUV.stddev().eval()
                # sUV is batched distrbution, there are issues making
                # Mixture with batch distributions. mvn0
                # with event size (D, N + M) and batch size ()
                # NOTE log_prob(sample) still returns tensor
                # mvn and multivariatenormaldiag work for 1-D not 2-D shapes
                sUV_mv = coreutils.base_loc_scale('mvn0',
                                                  loc_s,
                                                  scale_s,
                                                  multivariate=False)
                # TODO send sUV or sUV_mv as argument to step size? sample
                # works the same way. same with log_prob

                total_time = 0.
                data = {R: R_true, I: I_train}
                if t == 0:
                    gamma = 1.
                    lipschitz_estimate = opt.adafw_linit()
                    step_type = 'init'
                elif FLAGS.fw_variant == 'fixed':
                    start_step_time = time.time()
                    step_result = opt.fixed(weights, qUVt_components, qUV_prev,
                                            loc_s, scale_s, sUV, p_joint, data,
                                            t)
                    end_step_time = time.time()
                    total_time += float(end_step_time - start_step_time)
                elif FLAGS.fw_variant == 'line_search':
                    start_step_time = time.time()
                    step_result = opt.line_search_dkl(weights, qUVt_components,
                                                      qUV_prev, loc_s, scale_s,
                                                      sUV, p_joint, data, t)
                    end_step_time = time.time()
                    total_time += float(end_step_time - start_step_time)
                elif FLAGS.fw_variant == 'adafw':
                    start_step_time = time.time()
                    step_result = opt.adaptive_fw(weights, qUVt_components,
                                                  qUV_prev, loc_s, scale_s,
                                                  sUV, p_joint, data, t,
                                                  lipschitz_estimate)
                    end_step_time = time.time()
                    total_time += float(end_step_time - start_step_time)

                    step_type = step_result['step_type']
                    if step_type == 'adaptive':
                        lipschitz_estimate = step_result['l_estimate']
                elif FLAGS.fw_variant == 'ada_pfw':
                    start_step_time = time.time()
                    step_result = opt.adaptive_pfw(weights, qUVt_components,
                                                   qUV_prev, loc_s, scale_s,
                                                   sUV, p_joint, data, t,
                                                   lipschitz_estimate)
                    end_step_time = time.time()
                    total_time += float(end_step_time - start_step_time)

                    step_type = step_result['step_type']
                    if step_type in ['adaptive', 'drop']:
                        lipschitz_estimate = step_result['l_estimate']
                elif FLAGS.fw_variant == 'ada_afw':
                    start_step_time = time.time()
                    step_result = opt.adaptive_pfw(weights, qUVt_components,
                                                   qUV_prev, loc_s, scale_s,
                                                   sUV, p_joint, data, t,
                                                   lipschitz_estimate)
                    end_step_time = time.time()
                    total_time += float(end_step_time - start_step_time)

                    step_type = step_result['step_type']
                    if step_type in ['adaptive', 'away', 'drop']:
                        lipschitz_estimate = step_result['l_estimate']

                if t == 0:
                    gamma = 1.
                    weights.append(gamma)
                    qUVt_components.append({'loc': loc_s, 'scale': scale_s})
                    new_components = [sUV_mv]
                else:
                    qUVt_components = step_result['params']
                    weights = step_result['weights']
                    gamma = step_result['gamma']
                    new_components = [
                        coreutils.base_loc_scale('mvn0',
                                                 c['loc'],
                                                 c['scale'],
                                                 multivariate=False)
                        for c in qUVt_components
                    ]

                qUV_new = coreutils.get_mixture(weights, new_components)

                #qR = Normal(
                #    loc=tf.matmul(
                #        tf.transpose(qUV_new[:, :N]), qUV_new[:, N:]),
                #    scale=tf.ones([N, M]))
                qR = ed.copy(R, {UV: qUV_new})
                cR = ed.copy(R_mask, {UV: qUV_new})  # reconstructed matrix

                # Log metrics for current iteration
                logger.info('total time %f' % total_time)
                append_to_file(times_filename, total_time)

                logger.info('iter %d, gamma %.4f' % (t, gamma))
                append_to_file(step_filename, gamma)

                if t > 0:
                    gap_t = step_result['gap']
                    logger.info('iter %d, gap %.4f' % (t, gap_t))
                    append_to_file(gap_filename, gap_t)

                # CRITICISM
                if FLAGS.fw_variant.startswith('ada'):
                    append_to_file(lipschitz_filename, lipschitz_estimate)
                    append_to_file(iter_info_filename, step_type)
                    logger.info('lt = %.5f, iter_type = %s' %
                                (lipschitz_estimate, step_type))

                test_mse = ed.evaluate('mean_squared_error',
                                       data={
                                           cR: R_true,
                                           I: I_test
                                       })
                logger.info("iter %d ed test mse %.5f" % (t, test_mse))
                append_to_file(mse_test_filename, test_mse)

                train_mse = ed.evaluate('mean_squared_error',
                                        data={
                                            cR: R_true,
                                            I: I_train
                                        })
                logger.info("iter %d ed train mse %.5f" % (t, train_mse))
                append_to_file(mse_train_filename, train_mse)

                # very slow
                #train_ll = log_likelihood(qUV_new, R_true, I_train, sess, D, N,
                #                          M)
                train_ll = ed.evaluate('log_lik',
                                       data={
                                           qR: R_true.astype(np.float32),
                                           I: I_train
                                       })
                logger.info("iter %d train log lik %.5f" % (t, train_ll))
                append_to_file(ll_train_filename, train_ll)

                #test_ll = log_likelihood(qUV_new, R_true, I_test, sess, D, N, M)
                test_ll = ed.evaluate('log_lik',
                                      data={
                                          qR: R_true.astype(np.float32),
                                          I: I_test
                                      })
                logger.info("iter %d test log lik %.5f" % (t, test_ll))
                append_to_file(ll_test_filename, test_ll)

                # elbo_loss might be meaningless
                elbo_loss = elboModel.KLqp({UV: qUV_new},
                                           data={
                                               R: R_true,
                                               I: I_train
                                           })
                elbo_t = elbo(qUV_new, p_joint)
                res_update = elbo_loss.run()
                logger.info('iter %d -elbo loss %.2f or %.2f' %
                            (t, res_update['loss'], elbo_t))
                append_to_file(elbos_filename,
                               "%f,%f" % (elbo_t, res_update['loss']))

                # serialize the current iterate
                np.savez(os.path.join(outdir, 'qt_latest.npz'),
                         weights=weights,
                         comps=qUVt_components,
                         fw_iter=t + 1)

                sess.close()
        tf.reset_default_graph()
예제 #3
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def adaptive_pfw(weights, params, q_t, mu_s, cov_s, s_t, p, data, k, l_prev):
    """Adaptive pairwise variant.
    
    Args:
        weights: [k], weights of the mixture components of q_t
        params: list containing dictionary of mixture params ('mu', 'scale')
        q_t: current mixture iterate q_t
        mu_s: [dim], mean for LMO solution s
        cov_s: [dim], cov matrix for LMO solution s
        s_t: Current atom & LMO Solution s
        p: joint distribution p(z, x)
        data: training data
        k: iteration number of Frank-Wolfe
        l_prev: previous lipschitz estimate
        gap: Duality-Gap (if already computed)
    Returns:
        a dictionary containing gamma, new weights, new parameters
        lipschitz estimate, duality gap of current iterate
        and step information
    """
    d_t_norm = divergence(s_t, q_t, metric=FLAGS.distance_metric)
    logger.info('\ndistance norm is %.3e' % d_t_norm)

    # Find v_t
    qcomps = q_t.components
    index_v_t, step_v_t = argmax_grad_dotp(p, q_t, qcomps)
    v_t = qcomps[index_v_t]

    # Pairwise gap
    step_s = grad_kl_dotp(q_t, p, s_t)
    gap_pw = step_v_t - step_s
    logger.info('Pairwise gap %.3e' % gap_pw)
    if gap_pw <= 0:
        logger.warning('Pairwise gap <= 0, returning fixed step')
        return fixed(weights, params, q_t, mu_s, cov_s, s_t, p, data, k,
                     gap_pw)

    gap = gap_pw
    MAX_GAMMA = weights[index_v_t]

    gamma = 2. / (k + 2.)
    tau = FLAGS.exp_adafw
    eta = FLAGS.damping_adafw
    pow_tau = 1.0
    i, l_t = 0, l_prev
    f_t = -elbo(q_t, p)
    debug('f(q_t) = %.3e' % f_t)
    is_drop_step = False
    while gamma >= MIN_GAMMA and i < FLAGS.adafw_MAXITER:
        # compute L_t and gamma_t
        l_t = pow_tau * eta * l_prev
        gamma = min(gap / (l_t * d_t_norm), MAX_GAMMA)

        d_1 = -gamma * gap
        d_2 = gamma * gamma * l_t * d_t_norm / 2.
        debug('linear d1 = %.5f, quad d2 = %.5f' % (d_1, d_2))
        quad_bound_rhs = f_t + d_1 + d_2

        # construct q_{t + 1}
        # handle the case of MAX_GAMMA separately
        new_weights = copy.copy(weights)
        new_weights.append(gamma)
        new_params = copy.copy(params)
        new_params.append({'loc': mu_s, 'scale': cov_s})
        if gamma != MAX_GAMMA:
            new_weights[index_v_t] -= gamma
            is_drop_step = False
        else:
            # hardcoding to 0
            del new_weights[index_v_t]
            del new_params[index_v_t]
            is_drop_step = True

        new_components = [
            coreutils.base_loc_scale(FLAGS.base_dist,
                                     c['loc'],
                                     c['scale'],
                                     multivariate=False) for c in new_params
        ]

        qt_new = coreutils.get_mixture(new_weights, new_components)
        quad_bound_lhs = -elbo(qt_new, p)
        logger.info('lt = %.3e, gamma = %.3f, f_(qt_new) = %.3e, '
                    'linear extrapolated = %.3e' %
                    (l_t, gamma, quad_bound_lhs, quad_bound_rhs))
        if quad_bound_lhs <= quad_bound_rhs:
            # Adaptive loop succeeded
            return {
                'gamma': gamma,
                'l_estimate': l_t,
                'weights': new_weights,
                'params': new_params,
                'gap': gap,
                'step_type': 'drop' if is_drop_step else 'adaptive'
            }
        pow_tau *= tau
        i += 1

    # gamma below MIN_GAMMA
    logger.warning("gamma below threshold value, returning fixed step")
    return fixed(weights, params, q_t, mu_s, cov_s, s_t, p, data, k, gap)
예제 #4
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def adaptive_afw(weights, params, q_t, mu_s, cov_s, s_t, p, data, k, l_prev):
    """Adaptive Away Steps algorithm.

    Args:
        weights: [k], weights of the mixture components of q_t
        params: list containing dictionary of mixture params ('mu', 'scale')
        q_t: current mixture iterate q_t
        mu_s: [dim], mean for LMO solution s
        cov_s: [dim], cov matrix for LMO solution s
        s_t: Current atom & LMO Solution s
        p: joint distribution p(z, x)
        data: training data
        k: iteration number of Frank-Wolfe
        l_prev: previous lipschitz estimate
    Returns:
        a dictionary containing gamma, new weights, new parameters
        lipschitz estimate, duality gap of current iterate
        and step information
    """
    d_t_norm = divergence(s_t, q_t, metric=FLAGS.distance_metric)
    logger.info('\ndistance norm is %.3e' % d_t_norm)

    # Find v_t
    qcomps = q_t.components
    index_v_t, step_v_t = argmax_grad_dotp(p, q_t, qcomps)
    v_t = qcomps[index_v_t]

    # Frank-Wolfe gap
    step_s = grad_kl_dotp(q_t, p, s_t)
    step_q = grad_kl_dotp(q_t, p, q_t)
    gap_fw = step_q - step_s
    if gap_fw < 0: logger.warning("Frank-Wolfe duality gap is negative")
    # Away gap
    gap_a = step_v_t - step_q
    if gap_a < 0: eprint('Away gap < 0!!!')
    logger.info('fw gap %.3e, away gap %.3e' % (gap_fw, gap_a))

    if (gap_fw >= gap_a) or (len(params) == 1):
        # FW direction, proceeds exactly as adafw
        logger.info('Proceeding in FW direction ')
        return adaptive_fw(weights, params, q_t, mu_s, cov_s, s_t, p, data, k,
                           l_prev, gap_fw)

    # Away direction
    logger.info('Proceeding in Away direction ')
    adaptive_step_type = 'away'
    gap = gap_a
    if weights[index_v_t] < 1.0:
        MAX_GAMMA = weights[index_v_t] / (1.0 - weights[index_v_t])
    else:
        MAX_GAMMA = 100.  # Large value when t = 1

    gamma = 2. / (k + 2.)
    tau = FLAGS.exp_adafw
    eta = FLAGS.damping_adafw
    pow_tau = 1.0
    i, l_t = 0, l_prev
    f_t = -elbo(q_t, p)
    debug('f(q_t) = %.5f' % (f_t))
    is_drop_step = False
    while gamma >= MIN_GAMMA and i < FLAGS.adafw_MAXITER:
        # compute $L_t$ and $\gamma_t$
        l_t = pow_tau * eta * l_prev
        # NOTE: Handle extreme values of gamma carefully
        gamma = min(gap / (l_t * d_t_norm), MAX_GAMMA)

        d_1 = -gamma * gap
        d_2 = gamma * gamma * l_t * d_t_norm / 2.
        debug('linear d1 = %.5f, quad d2 = %.5f' % (d_1, d_2))
        quad_bound_rhs = f_t + d_1 + d_2

        # construct $q_{t + 1}$
        new_weights = copy.copy(weights)
        new_params = copy.copy(params)
        if gamma == MAX_GAMMA:
            # drop v_t
            is_drop_step = True
            del new_weights[index_v_t]
            new_weights = [(1. + gamma) * w for w in new_weights]
            del new_params[index_v_t]
        else:
            is_drop_step = False
            new_weights = [(1. + gamma) * w for w in new_weights]
            new_weights[index_v_t] -= gamma

        new_components = [
            coreutils.base_loc_scale(FLAGS.base_dist,
                                     c['loc'],
                                     c['scale'],
                                     multivariate=False) for c in new_params
        ]

        qt_new = coreutils.get_mixture(new_weights, new_components)
        quad_bound_lhs = -elbo(qt_new, p)
        logger.info('lt = %.3e, gamma = %.3f, f_(qt_new) = %.3e, '
                    'linear extrapolated = %.3e' %
                    (l_t, gamma, quad_bound_lhs, quad_bound_rhs))
        if quad_bound_lhs <= quad_bound_rhs:
            return {
                'gamma': gamma,
                'l_estimate': l_t,
                'weights': new_weights,
                'params': new_params,
                'gap': gap,
                'step_type': "drop" if is_drop_step else "away"
            }
        pow_tau *= tau
        i += 1

    # gamma below MIN_GAMMA
    logger.warning("gamma below threshold value, returning fixed step")
    return fixed(weights, params, q_t, mu_s, cov_s, s_t, p, data, k, gap)
예제 #5
0
def adaptive_fw(weights,
                params,
                q_t,
                mu_s,
                cov_s,
                s_t,
                p,
                data,
                k,
                l_prev,
                gap=None):
    """Adaptive Frank-Wolfe algorithm.
    
    Sets step size as suggested in Algorithm 1 of
    https://arxiv.org/pdf/1806.05123.pdf

    Args:
        weights: [k], weights of the mixture components of q_t
        params: list containing dictionary of mixture params ('mu', 'scale')
        q_t: current mixture iterate q_t
        mu_s: [dim], mean for LMO solution s
        cov_s: [dim], cov matrix for LMO solution s
        s_t: Current atom & LMO Solution s
        p: joint distribution p(z, x)
        data: training data
        k: iteration number of Frank-Wolfe
        l_prev: previous lipschitz estimate
        gap: Duality-Gap (if already computed)
    Returns:
        a dictionary containing gamma, new weights, new parameters
        lipschitz estimate, duality gap of current iterate
        and step information
    """

    # NOTE TODO try div(q_t, s_t)
    d_t_norm = divergence(s_t, q_t, metric=FLAGS.distance_metric)
    logger.info('\ndistance norm is %.3e' % d_t_norm)

    if gap is None:
        step_s = grad_kl_dotp(q_t, p, s_t)
        step_q = grad_kl_dotp(q_t, p, q_t)
        gap = step_q - step_s
    logger.info('duality gap %.3e' % gap)
    if gap < 0:
        logger.warning("Duality gap is negative returning fixed step")
        return fixed(weights, params, q_t, mu_s, cov_s, s_t, p, data, k, gap)

    gamma = 2. / (k + 2.)
    tau = FLAGS.exp_adafw
    eta = FLAGS.damping_adafw
    # NOTE: this is from v1 of the paper, new version
    # replaces multiplicative eta with divisor eta
    pow_tau = 1.0
    i, l_t = 0, l_prev

    # Objective in this case is -ELBO, elbo loss
    def neg_elbo(q):
        elbo_loss = elboModel.KLqp({pz: q}, data)
        return elbo_loss.run()['loss']

    f_t = -elbo(q_t, p)

    debug('f(q_t) = %.3e' % (f_t))
    # return intial estimate if gap is -ve
    while gamma >= MIN_GAMMA and i < FLAGS.adafw_MAXITER:
        # compute $L_t$ and $\gamma_t$
        l_t = pow_tau * eta * l_prev
        gamma = min(gap / (l_t * d_t_norm), 1.0)
        d_1 = -gamma * gap
        d_2 = gamma * gamma * l_t * d_t_norm / 2.
        #debug('linear d1 = %.3e, quad d2 = %.3e' % (d_1, d_2))
        quad_bound_rhs = f_t + d_1 + d_2

        # $w_{t + 1} = [(1 - \gamma)w_t, \gamma]$
        # Handling the case of gamma = 1.0
        # separately, weights might not get exactly 0 because
        # of precision issues. 0 wt components should be removed
        if gamma != 1.0:
            new_weights = copy.copy(weights)
            new_weights = [(1. - gamma) * w for w in new_weights]
            new_weights.append(gamma)
            new_params = copy.copy(params)
            new_params.append({'loc': mu_s, 'scale': cov_s})
        else:
            new_weights = [1.]
            new_params = [{'loc': mu_s, 'scale': cov_s}]

        new_components = [
            coreutils.base_loc_scale(FLAGS.base_dist,
                                     c['loc'],
                                     c['scale'],
                                     multivariate=False) for c in new_params
        ]

        qt_new = coreutils.get_mixture(new_weights, new_components)
        quad_bound_lhs = -elbo(qt_new, p)
        #quad_bound_lhs = neg_elbo(qt_new)
        logger.info('lt = %.3e, gamma = %.3f, f_(qt_new) = %.3e, '
                    'linear extrapolated = %.3e' %
                    (l_t, gamma, quad_bound_lhs, quad_bound_rhs))
        if quad_bound_lhs <= quad_bound_rhs:
            # Adaptive loop succeeded
            return {
                'gamma': gamma,
                'l_estimate': l_t,
                'weights': new_weights,
                'params': new_params,
                'gap': gap,
                'step_type': 'adaptive'
            }
        pow_tau *= tau
        i += 1

    # gamma below MIN_GAMMA
    logger.warning("gamma below threshold value, returning fixed step")
    return fixed(weights, params, q_t, mu_s, cov_s, s_t, p, data, k, gap)