From cc8569fcd243d7c96a20e0f531f6f97a90df83f7 Mon Sep 17 00:00:00 2001
From: Fredrik Svedberg <fredrik.svedberg@arm.com>
Date: Mon, 1 Nov 2021 14:25:29 +0100
Subject: MLBEDSW-5209 Vela: output diff depthwise with non-zero zero points

Fixed by adjusting zero points for ops with int8 IFM and asymmetric weights
since the reference does not support asymmetric weights for int8 IFM and
ignores the zero points.

Signed-off-by: Fredrik Svedberg <fredrik.svedberg@arm.com>
Change-Id: I2a206a01a471a53aa864a6a3616aa23d2a5a23c8
---
 ethosu/vela/tensor.py                 | 14 +++++++++++++-
 ethosu/vela/tflite_graph_optimiser.py | 11 +++++++++++
 ethosu/vela/tflite_reader.py          |  1 +
 ethosu/vela/tflite_writer.py          |  2 ++
 4 files changed, 27 insertions(+), 1 deletion(-)

(limited to 'ethosu/vela')

diff --git a/ethosu/vela/tensor.py b/ethosu/vela/tensor.py
index d62ebc8e..8c5e277a 100644
--- a/ethosu/vela/tensor.py
+++ b/ethosu/vela/tensor.py
@@ -209,7 +209,17 @@ def create_equivalence_id(key) -> UUID:
 
 
 class QuantizationParameters:
-    __slots__ = "min", "max", "num_bits", "narrow_range", "scale_f32", "zero_point", "quant_min", "quant_max"
+    __slots__ = (
+        "min",
+        "max",
+        "num_bits",
+        "narrow_range",
+        "scale_f32",
+        "zero_point",
+        "quant_min",
+        "quant_max",
+        "quant_dim",
+    )
 
     def __init__(
         self,
@@ -228,6 +238,7 @@ class QuantizationParameters:
         self.zero_point: Union[int, np.ndarray, None] = None
         self.quant_min: Optional[float] = None
         self.quant_max: Optional[float] = None
+        self.quant_dim: Optional[int] = None
 
     def __str__(self):
         return "<nng.QuantizationParameters min=%s max=%s, num_bits=%s, scale=%s, zero_point=%s>" % (
@@ -252,6 +263,7 @@ class QuantizationParameters:
         res.zero_point = self.zero_point
         res.quant_min = self.quant_min
         res.quant_max = self.quant_max
+        res.quant_dim = self.quant_dim
         return res
 
     def dequantize(self, values) -> np.ndarray:
diff --git a/ethosu/vela/tflite_graph_optimiser.py b/ethosu/vela/tflite_graph_optimiser.py
index 2469a700..e01433d0 100644
--- a/ethosu/vela/tflite_graph_optimiser.py
+++ b/ethosu/vela/tflite_graph_optimiser.py
@@ -1152,6 +1152,16 @@ def fixup_bias_tensors(op, arch, nng):
     return op
 
 
+def fixup_asymmetric_weights(op, arch, nng):
+    if op.run_on_npu and (op.type.is_conv2d_op() or op.type.is_depthwise_conv2d_op()):
+        if op.ifm.dtype == DataType.int8:
+            if not np.all(op.weights.quantization.zero_point == 0):
+                print(f"Warning: {op.type} '{op.name}' has asymmetric weights, zero points have been adjusted.")
+                op.weights.quantization.zero_point *= 0
+
+    return op
+
+
 def convert_mean_to_depthwise_conv_or_avgpool(op, arch, nng):
     if op.type == Op.Mean and op.run_on_npu:
         keep_dims = op.attrs.get("keep_dims", False)
@@ -1405,6 +1415,7 @@ def tflite_optimise_graph(nng, arch):
         reorder_depthwise_weights,
         fixup_resizebilinear,
         fixup_bias_tensors,
+        fixup_asymmetric_weights,
         convert_mul_max_to_abs_or_lrelu,
         convert_lrelu,
         convert_tanh_sigmoid_to_lut,
diff --git a/ethosu/vela/tflite_reader.py b/ethosu/vela/tflite_reader.py
index fbee7930..8dc5efe1 100644
--- a/ethosu/vela/tflite_reader.py
+++ b/ethosu/vela/tflite_reader.py
@@ -88,6 +88,7 @@ class TFLiteSubgraph:
             tens.quantization.max = self.len1_array_to_scalar(quant.MaxAsNumpy())
             tens.quantization.scale_f32 = self.len1_array_to_scalar(quant.ScaleAsNumpy())
             tens.quantization.zero_point = self.len1_array_to_scalar(quant.ZeroPointAsNumpy())
+            tens.quantization.quant_dim = quant.QuantizedDimension()
 
         if dtype == DataType.uint8:
             tens.quantization.quant_min = 0
diff --git a/ethosu/vela/tflite_writer.py b/ethosu/vela/tflite_writer.py
index e6dd85b5..d134c07c 100644
--- a/ethosu/vela/tflite_writer.py
+++ b/ethosu/vela/tflite_writer.py
@@ -236,6 +236,8 @@ class TFLiteSerialiser:
                 QuantizationParameters.QuantizationParametersAddScale(builder, scale)
             if zero_point is not None:
                 QuantizationParameters.QuantizationParametersAddZeroPoint(builder, zero_point)
+            if quant.quant_dim is not None:
+                QuantizationParameters.QuantizationParametersAddQuantizedDimension(builder, quant.quant_dim)
             qp = QuantizationParameters.QuantizationParametersEnd(builder)
 
         return qp
-- 
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