From 46d631759f59bc6b65458202641e5f5a9bc30b7b Mon Sep 17 00:00:00 2001
From: Volpeon <git@volpeon.ink>
Date: Mon, 2 Jan 2023 20:13:59 +0100
Subject: Fixed LR finder

---
 training/lr.py | 38 +++++++++++++++++++++-----------------
 1 file changed, 21 insertions(+), 17 deletions(-)

(limited to 'training/lr.py')

diff --git a/training/lr.py b/training/lr.py
index fe166ed..acc01a2 100644
--- a/training/lr.py
+++ b/training/lr.py
@@ -1,6 +1,7 @@
 import math
 import copy
 from typing import Callable
+from functools import partial
 
 import matplotlib.pyplot as plt
 import numpy as np
@@ -41,7 +42,7 @@ class LRFinder():
 
     def run(
         self,
-        min_lr,
+        end_lr,
         skip_start: int = 10,
         skip_end: int = 5,
         num_epochs: int = 100,
@@ -57,7 +58,7 @@ class LRFinder():
         losses = []
         accs = []
 
-        lr_scheduler = get_exponential_schedule(self.optimizer, min_lr, num_epochs)
+        lr_scheduler = get_exponential_schedule(self.optimizer, end_lr, num_epochs)
 
         steps = min(num_train_batches, len(self.train_dataloader))
         steps += min(num_val_batches, len(self.val_dataloader))
@@ -152,29 +153,30 @@ class LRFinder():
                 print("Stopping early, the loss has diverged")
                 break
 
-        if skip_end == 0:
-            lrs = lrs[skip_start:]
-            losses = losses[skip_start:]
-            accs = accs[skip_start:]
-        else:
-            lrs = lrs[skip_start:-skip_end]
-            losses = losses[skip_start:-skip_end]
-            accs = accs[skip_start:-skip_end]
-
         fig, ax_loss = plt.subplots()
+        ax_acc = ax_loss.twinx()
 
         ax_loss.plot(lrs, losses, color='red')
         ax_loss.set_xscale("log")
-        ax_loss.set_xlabel("Learning rate")
+        ax_loss.set_xlabel(f"Learning rate")
         ax_loss.set_ylabel("Loss")
 
-        ax_acc = ax_loss.twinx()
         ax_acc.plot(lrs, accs, color='blue')
+        ax_acc.set_xscale("log")
         ax_acc.set_ylabel("Accuracy")
 
         print("LR suggestion: steepest gradient")
         min_grad_idx = None
 
+        if skip_end == 0:
+            lrs = lrs[skip_start:]
+            losses = losses[skip_start:]
+            accs = accs[skip_start:]
+        else:
+            lrs = lrs[skip_start:-skip_end]
+            losses = losses[skip_start:-skip_end]
+            accs = accs[skip_start:-skip_end]
+
         try:
             min_grad_idx = (np.gradient(np.array(losses))).argmin()
         except ValueError:
@@ -196,8 +198,10 @@ class LRFinder():
             ax_loss.legend()
 
 
-def get_exponential_schedule(optimizer, min_lr, num_epochs, last_epoch=-1):
-    def lr_lambda(current_epoch: int):
-        return min_lr + ((current_epoch / num_epochs) ** 10) * (1 - min_lr)
+def get_exponential_schedule(optimizer, end_lr: float, num_epochs: int, last_epoch: int = -1):
+    def lr_lambda(base_lr: float, current_epoch: int):
+        return (end_lr / base_lr) ** (current_epoch / num_epochs)
+
+    lr_lambdas = [partial(lr_lambda, group["lr"]) for group in optimizer.param_groups]
 
-    return LambdaLR(optimizer, lr_lambda, last_epoch)
+    return LambdaLR(optimizer, lr_lambdas, last_epoch)
-- 
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