fix save and reload model state (#49)

Co-authored-by: Srini Iyer <sviyer@meta.com>

bytelatent/model/local_models.py

@@ -74,12 +74,10 @@ class LocalModelBase(nn.Module):
 
         self.boe_id = BOE_ID
 
-        self.norm = RMSNorm(args.dim, eps=args.norm_eps)
         self.layers = nn.ModuleList(
             [TransformerBlock(args) for _ in range(args.n_layers)]
         )
 
-        self.tok_embeddings = nn.Embedding(self.vocab_size, args.dim)
         if not self.use_rope:
             self.pos_embeddings = nn.Embedding(args.max_length, args.dim)
         else:
@@ -131,16 +129,18 @@ class LocalModelBase(nn.Module):
 
     def init_weights(self, init_std=None):
         self.rope.reset_parameters()
-        self.norm.reset_parameters()
+        if hasattr(self, "norm"):
+            self.norm.reset_parameters()
 
         init_std = init_std or (self.dim ** (-0.5))
-        nn.init.trunc_normal_(
-            self.tok_embeddings.weight,
-            mean=0.0,
-            std=init_std,
-            a=-3 * init_std,
-            b=3 * init_std,
-        )
+        if hasattr(self, "tok_embeddings"):
+            nn.init.trunc_normal_(
+                self.tok_embeddings.weight,
+                mean=0.0,
+                std=init_std,
+                a=-3 * init_std,
+                b=3 * init_std,
+            )
         if self.pos_embeddings is not None:
             nn.init.trunc_normal_(
                 self.pos_embeddings.weight,
@@ -212,6 +212,8 @@ class LocalEncoder(LocalModelBase):
         self.cross_attn_init_by_pooling = args.cross_attn_init_by_pooling
         self.cross_attn_nheads = args.cross_attn_nheads
 
+        self.tok_embeddings = nn.Embedding(self.vocab_size, args.dim)
+
         if self.cross_attn_encoder:
             self.cross_attn_layers = torch.nn.ModuleList()
             layers_to_add = args.n_layers if self.cross_attn_all_layers_encoder else 1
@@ -314,6 +316,8 @@ class LocalDecoder(LocalModelBase):
         self.cross_attn_init_by_pooling = args.cross_attn_init_by_pooling
         self.cross_attn_nheads = args.cross_attn_nheads
 
+        self.norm = RMSNorm(args.dim, eps=args.norm_eps)
+
         if self.cross_attn_decoder:
             self.cross_attn_layers = torch.nn.ModuleList()
             layers_to_add = args.n_layers if self.cross_attn_all_layers_decoder else 1