Explicitly set `weight_decay` value (#8592)

* explicitly set weight_decay value The default weight_decay value of AdamW is 1e-2, so we should set it to zero. * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci * Cleanup Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com> Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>

Explicitly set `weight_decay` value (#8592)
7204c1ca · Yonghye Kwon · GitHub · 72a81e7a · 7204c1ca
--- a/train.py
+++ b/train.py
@@ -163,12 +163,12 @@ def train(hyp, opt, device, callbacks):  # hyp is path/to/hyp.yaml or hyp dictio
    if opt.optimizer == 'Adam':
        optimizer = Adam(g[2], lr=hyp['lr0'], betas=(hyp['momentum'], 0.999))  # adjust beta1 to momentum
    elif opt.optimizer == 'AdamW':
-        optimizer = AdamW(g[2], lr=hyp['lr0'], betas=(hyp['momentum'], 0.999))  # adjust beta1 to momentum
+        optimizer = AdamW(g[2], lr=hyp['lr0'], betas=(hyp['momentum'], 0.999), weight_decay=0.0)
    else:
        optimizer = SGD(g[2], lr=hyp['lr0'], momentum=hyp['momentum'], nesterov=True)
    optimizer.add_param_group({'params': g[0], 'weight_decay': hyp['weight_decay']})  # add g0 with weight_decay
-    optimizer.add_param_group({'params': g[1]})  # add g1 (BatchNorm2d weights)
+    optimizer.add_param_group({'params': g[1], 'weight_decay': 0.0})  # add g1 (BatchNorm2d weights)
    LOGGER.info(f"{colorstr('optimizer:')} {type(optimizer).__name__} with parameter groups "
                f"{len(g[1])} weight (no decay), {len(g[0])} weight, {len(g[2])} bias")
    del g