diff --git a/onn/optimizer.py b/onn/optimizer.py
index 14d0d1e..2aa05f8 100644
--- a/onn/optimizer.py
+++ b/onn/optimizer.py
@@ -248,141 +248,6 @@ class MomentumClip(Optimizer):
             return -self.lr * self.accum
 
 
-class YellowFin(Optimizer):
-    # paper: https://arxiv.org/abs/1706.03471
-    # knowyourmeme: http://cs.stanford.edu/~zjian/project/YellowFin/
-    # author's implementation:
-    # https://github.com/JianGoForIt/YellowFin/blob/master/tuner_utils/yellowfin.py
-    # code lifted:
-    # https://gist.github.com/botev/f8b32c00eafee222e47393f7f0747666
-
-    def __init__(self, lr=0.1, mu=0.0, beta=0.999, window_size=20,
-                 debias=True, clip=1.0):
-        self.lr_default = _f(lr)
-        self.mu_default = _f(mu)
-        self.beta = _f(beta)
-        self.window_size = int(window_size)  # curv_win_width
-        self.debias_enabled = bool(debias)
-        self.clip = _f(clip)
-
-        self.mu = _f(mu)  # momentum
-        super().__init__(lr)
-
-    def reset(self):
-        self.accum = None
-
-        self.lr = self.lr_default
-        self.mu = self.mu_default
-
-        self.step = 0
-        self.beta_t = self.beta
-
-        self.curv_win = np.zeros([self.window_size, ], dtype=np.float32)
-
-        self.h_min = None
-        self.h_max = None
-
-        self.g_lpf = 0
-        # self.g_squared_lpf = 0
-        self.g_norm_squared_lpf = 0
-        self.g_norm_lpf = 0
-        self.h_min_lpf = 0
-        self.h_max_lpf = 0
-        self.dist_lpf = 0
-        self.lr_lpf = 0
-        self.mu_lpf = 0
-
-    def get_lr_mu(self):
-        p = (np.square(self.dist_avg) * np.square(self.h_min)) \
-            / (2 * self.g_var)
-        w3 = p * (np.sqrt(0.25 + p / 27.0) - 0.5)
-        w = np.power(w3, 1/3)
-        y = w - p / (3 * w)
-        sqrt_mu1 = y + 1
-
-        sqrt_h_min = np.sqrt(self.h_min)
-        sqrt_h_max = np.sqrt(self.h_max)
-        sqrt_mu2 = (sqrt_h_max - sqrt_h_min) / (sqrt_h_max + sqrt_h_min)
-
-        sqrt_mu = max(sqrt_mu1, sqrt_mu2)
-        if sqrt_mu2 > sqrt_mu1:
-            print('note: taking dr calculation. something may have exploded.')
-
-        lr = np.square(1 - sqrt_mu) / self.h_min
-        mu = np.square(sqrt_mu)
-        return lr, mu
-
-    def compute(self, dW, W):
-        if self.accum is None:
-            self.accum = np.zeros_like(dW)
-
-        # TODO: prevent allocations everywhere by using [:].
-        #       assuming that really works. i haven't actually checked.
-
-        total_norm = np.linalg.norm(dW)
-        clip_scale = self.clip / (total_norm + 1e-6)
-        if clip_scale < 1:
-            # print("clipping gradients; norm: {:10.5f}".format(total_norm))
-            dW *= clip_scale
-
-        # fmt = 'W std: {:10.7f}e-3,  dWstd: {:10.7f}e-3,  V std: {:10.7f}e-3'
-        # print(fmt.format(np.std(W), np.std(dW) * 100, np.std(V) * 100))
-
-        b = self.beta
-        m1b = 1 - self.beta
-        debias = 1 / (1 - self.beta_t) if self.debias_enabled else 1
-
-        g = dW
-        g_squared = np.square(g)
-        g_norm_squared = np.sum(g_squared)
-        g_norm = np.sqrt(g_norm_squared)
-
-        self.curv_win[self.step % self.window_size] = g_norm_squared
-        valid_window = self.curv_win[:min(self.window_size, self.step + 1)]
-        h_min_t = np.min(valid_window)
-        h_max_t = np.max(valid_window)
-
-        self.g_lpf = b * self.g_lpf + m1b * g
-        # self.g_squared_lpf = b * self.g_squared_lpf + m1b * g_squared
-        self.g_norm_squared_lpf = b * self.g_norm_squared_lpf \
-            + m1b * g_norm_squared
-        self.g_norm_lpf = b * self.g_norm_lpf + m1b * g_norm
-        self.h_min_lpf = b * self.h_min_lpf + m1b * h_min_t
-        self.h_max_lpf = b * self.h_max_lpf + m1b * h_max_t
-
-        g_avg = debias * self.g_lpf
-        # g_squared_avg = debias * self.g_squared_lpf
-        g_norm_squared_avg = debias * self.g_norm_squared_lpf
-        g_norm_avg = debias * self.g_norm_lpf
-        self.h_min = debias * self.h_min_lpf
-        self.h_max = debias * self.h_max_lpf
-        assert self.h_max >= self.h_min
-
-        dist = g_norm_avg / g_norm_squared_avg
-
-        self.dist_lpf = b * self.dist_lpf + m1b * dist
-
-        self.dist_avg = debias * self.dist_lpf
-
-        self.g_var = g_norm_squared_avg - np.sum(np.square(g_avg))
-        # equivalently:
-        # self.g_var = np.sum(np.abs(g_squared_avg - np.square(g_avg)))
-
-        if self.step > 0:
-            lr_for_real, mu_for_real = self.get_lr_mu()
-            self.mu_lpf = b * self.mu_lpf + m1b * mu_for_real
-            self.lr_lpf = b * self.lr_lpf + m1b * lr_for_real
-            self.mu = debias * self.mu_lpf
-            self.lr = debias * self.lr_lpf
-
-        self.accum[:] = self.accum * self.mu - self.lr * dW
-        V = self.accum
-
-        self.step += 1
-        self.beta_t *= self.beta
-        return V
-
-
 class AddSign(Optimizer):
     # paper: https://arxiv.org/abs/1709.07417