Fix (example/quantizers): correct zero point handling

src/brevitas_examples/common/generative/quant_blocks.py

@@ -12,6 +12,8 @@
 import brevitas
 from brevitas.core.function_wrapper.shape import PermuteDims
 from brevitas.core.utils import SliceTensor
+from brevitas.core.zero_point import _ScaleShiftZeroPoint
+from brevitas.function.ops_ste import abs_binary_sign_grad
 
 
 class OverSubChannelBlockView(brevitas.jit.ScriptModule):
@@ -108,6 +110,32 @@ def forward(self, x) -> Tensor:
         return x
 
 
+class RuntimeDynamicStatsZeroPoint(brevitas.jit.ScriptModule):
+    __constants__ = ['dynamic_scaling_broadcastable_shape']
+
+    def __init__(
+            self,
+            zero_point_stats_impl: nn.Module,
+            int_quant: nn.Module,
+            quantize_zero_point: bool,
+            dynamic_scaling_broadcastable_shape: Tuple[int, ...],
+            zero_point_stats_input_view_shape_impl: nn.Module) -> None:
+        super(RuntimeDynamicStatsZeroPoint, self).__init__()
+        self.zero_point_stats_input_view_shape_impl = zero_point_stats_input_view_shape_impl
+        self.zero_point_stats_impl = zero_point_stats_impl
+        self.dynamic_scaling_broadcastable_shape = dynamic_scaling_broadcastable_shape
+        self.scale_shift_zero_point = _ScaleShiftZeroPoint(int_quant, quantize_zero_point)
+
+    @brevitas.jit.script_method
+    def forward(self, x, scale, bit_width) -> Tensor:
+        x = self.zero_point_stats_input_view_shape_impl(x)
+        x = self.zero_point_stats_impl(x)
+        x = x.view(self.dynamic_scaling_broadcastable_shape)
+        x = abs_binary_sign_grad(x)
+        x = self.scale_shift_zero_point(x, scale, bit_width)
+        return x
+
+
 class RuntimeDynamicGroupStatsScaling(brevitas.jit.ScriptModule):
 
     def __init__(self, group_size: int, group_dim: int, scaling_stats_impl: nn.Module) -> None:

src/brevitas_examples/common/generative/quantizers.py

@@ -162,5 +162,6 @@ class ShiftedUint8DynamicActPerTensorFloat(DynamicActProxyMixin, ShiftedUint8Act
     scaling_impl = RuntimeDynamicStatsScaling
     scaling_stats_input_view_shape_impl = OverTensorView
     scaling_stats_op = 'min_max'
+    zero_point_impl = RuntimeDynamicStatsZeroPoint
     zero_point_stats_impl = NegativeMinOrZero
     dynamic_scaling_broadcastable_shape = this.scaling_shape