Remove meta and enable uint8 quantization (#3222)

Fixes # .

### Description

Bug in dequantization meta removal, also enabling uint8 quantization

### Types of changes
<!--- Put an `x` in all the boxes that apply, and remove the not
applicable items -->
- [x] Non-breaking change (fix or new feature that would not break
existing functionality).
- [ ] Breaking change (fix or new feature that would cause existing
functionality to change).
- [ ] New tests added to cover the changes.
- [ ] Quick tests passed locally by running `./runtest.sh`.
- [ ] In-line docstrings updated.
- [ ] Documentation updated.

nvflare/app_opt/pt/quantization/dequantizor.py

@@ -178,20 +178,18 @@ def process_dxo(self, dxo: DXO, shareable: Shareable, fl_ctx: FLContext) -> Unio
         quantization_type = dxo.get_meta_prop(key=MetaKey.PROCESSED_ALGORITHM, default=None)
         if quantization_type.upper() not in QUANTIZATION_TYPE:
             raise ValueError(f"Invalid quantization type: {quantization_type}, valid: {QUANTIZATION_TYPE}")
-
+        source_datatype = dxo.get_meta_prop(key="source_datatype", default=None)
         dequantized_params = self.dequantization(
             params=dxo.data,
             quant_state=dxo.meta["quant_state"],
             quantization_type=quantization_type,
-            source_datatype=dxo.meta["source_datatype"],
+            source_datatype=source_datatype,
             fl_ctx=fl_ctx,
         )
         # Compose new DXO with dequantized data
         dxo.data = dequantized_params
-        dxo.remove_meta_props(MetaKey.PROCESSED_ALGORITHM)
-        dxo.remove_meta_props("quant_state")
-        dxo.remove_meta_props("source_datatype")
+        dxo.remove_meta_props([MetaKey.PROCESSED_ALGORITHM, "quant_state", "source_datatype", "quantized_flag"])
         dxo.update_shareable(shareable)
-        self.log_info(fl_ctx, "Dequantized back")
+        self.log_info(fl_ctx, f"Dequantized back to {source_datatype}")
 
         return dxo

nvflare/app_opt/pt/quantization/quantizor.py

@@ -195,13 +195,33 @@ def process_dxo(self, dxo: DXO, shareable: Shareable, fl_ctx: FLContext) -> Unio
         """
 
         self.log_info(fl_ctx, "Running quantization...")
-        quantized_params, quant_state, source_datatype = self.quantization(params=dxo.data, fl_ctx=fl_ctx)
-        # Compose new DXO with quantized data
-        # Add quant_state to the new DXO meta
-        new_dxo = DXO(data_kind=dxo.data_kind, data=quantized_params, meta=dxo.meta)
-        new_dxo.set_meta_prop(key=MetaKey.PROCESSED_ALGORITHM, value=self.quantization_type)
-        new_dxo.set_meta_prop(key="quant_state", value=quant_state)
-        new_dxo.set_meta_prop(key="source_datatype", value=source_datatype)
-        self.log_info(fl_ctx, f"Quantized to {self.quantization_type}")
+
+        # for already quantized message, skip quantization
+        # The reason in this current example:
+        # server job in this case is 1-N communication with identical quantization operation
+        # the first communication to client will apply quantization and change the data on the server
+        # thus the subsequent communications to the rest of clients will no longer need to apply quantization
+        # This will not apply to client job, since the client job will be 1-1 and quantization applies to each client
+        # Potentially:
+        # If clients talks to each other, it will also be 1-N and same rule applies
+        # If 1-N server-client filters can be different (Filter_1 applies to server-client_subset_1, etc.), then
+        # a deep copy of the server data should be made by filter before applying a different filter
+
+        # quantized_flag None if does not exist in meta
+        quantized_flag = dxo.get_meta_prop("quantized_flag")
+        if quantized_flag:
+            self.log_info(fl_ctx, "Already quantized, skip quantization")
+            new_dxo = dxo
+        else:
+            # apply quantization
+            quantized_params, quant_state, source_datatype = self.quantization(params=dxo.data, fl_ctx=fl_ctx)
+            # Compose new DXO with quantized data
+            # Add quant_state to the new DXO meta
+            new_dxo = DXO(data_kind=dxo.data_kind, data=quantized_params, meta=dxo.meta)
+            new_dxo.set_meta_prop(key=MetaKey.PROCESSED_ALGORITHM, value=self.quantization_type)
+            new_dxo.set_meta_prop(key="quant_state", value=quant_state)
+            new_dxo.set_meta_prop(key="source_datatype", value=source_datatype)
+            new_dxo.set_meta_prop(key="quantized_flag", value=True)
+            self.log_info(fl_ctx, f"Quantized from {source_datatype} to {self.quantization_type}")
 
         return new_dxo