Implimented MultiHeadAttention

model.py

@@ -1,12 +1,28 @@
 from tinygrad import Tensor,nn,TinyJit
 
 class MultiHeadAttention:
-    def __init__(self):
-        pass #TODO
-    def __call__(self):
-        pass #TODO
-    def cast(self):
-        pass #TODO
+    def __init__(self,embed_size,n_heads):
+        assert embed_size % n_heads == 0
+        self.head_size = embed_size//n_heads
+        self.n_heads = n_heads
+        self.qkv = nn.Linear(embed_size, embed_size*3,bias=False)
+        self.projection = nn.Linear(embed_size, embed_size,bias=False)
+    def __call__(self,x):
+        B,T,C=x.shape
+
+        q,k,v = self.qkv(x).chunk(3,dim=-1)
+        q = q.view(B, T, self.n_heads, self.head_size).transpose(1, 2)
+        k = k.view(B, T, self.n_heads, self.head_size).transpose(1, 2)
+        v = v.view(B, T, self.n_heads, self.head_size).transpose(1, 2)
+        #B H T S
+
+        out = q.scaled_dot_product_attention(k,v,is_causal=True,dropout_p=0.01)
+        out = out.transpose(1,2).view(B,T,C)
+        return self.projection(out)
+    def cast(self,dtype):
+        self.qkv.weight = self.qkv.weight.cast(dtype)
+        self.projection.weight = self.projection.weight.cast(dtype)
+        return self
 
 
 class FeedForwardNetwork: