From f2aaab3a06024b5d5c538cc42799fb2c91b4ca2b Mon Sep 17 00:00:00 2001
From: Matteo Martincigh <matteo.martincigh@arm.com>
Date: Thu, 6 Jun 2019 15:46:22 +0100
Subject: IVGCVSW-3223 Fix ref convolution performance regression

 * Do not use DataLayoutIndexed::GetIndex for weights and inputs,
   as it causes a large regression in performance
 * It turned out that the calculation of the indexes for the weights
   and inputs was the way it was because of an optimization done
   many months ago
 * Reverted the relevant hunks and added some comments so
   we won't make the same mistake again in the future
 * Made the GetIndex function inline to speed up other usages

Change-Id: I343b2ef0446993086f58b9dea1f0de0ba2d92216
Signed-off-by: Matteo Martincigh <matteo.martincigh@arm.com>
---
 src/armnnUtils/DataLayoutIndexed.hpp | 39 +++++++++++++++++++++++++++++++++---
 1 file changed, 36 insertions(+), 3 deletions(-)

(limited to 'src/armnnUtils/DataLayoutIndexed.hpp')

diff --git a/src/armnnUtils/DataLayoutIndexed.hpp b/src/armnnUtils/DataLayoutIndexed.hpp
index 5bb8e0d93f..8bd9701a5e 100644
--- a/src/armnnUtils/DataLayoutIndexed.hpp
+++ b/src/armnnUtils/DataLayoutIndexed.hpp
@@ -8,6 +8,8 @@
 #include <armnn/Types.hpp>
 #include <armnn/Tensor.hpp>
 
+#include <boost/assert.hpp>
+
 namespace armnnUtils
 {
 
@@ -21,9 +23,40 @@ public:
     unsigned int      GetChannelsIndex() const { return m_ChannelsIndex; }
     unsigned int      GetHeightIndex()   const { return m_HeightIndex; }
     unsigned int      GetWidthIndex()    const { return m_WidthIndex; }
-    unsigned int      GetIndex(const armnn::TensorShape& shape,
-                               unsigned int batchIndex, unsigned int channelIndex,
-                               unsigned int heightIndex, unsigned int widthIndex) const;
+
+    inline unsigned int GetIndex(const armnn::TensorShape& shape,
+                                 unsigned int batchIndex, unsigned int channelIndex,
+                                 unsigned int heightIndex, unsigned int widthIndex) const
+    {
+        BOOST_ASSERT( batchIndex < shape[0] || ( shape[0] == 0 && batchIndex == 0 ) );
+        BOOST_ASSERT( channelIndex < shape[m_ChannelsIndex] ||
+                    ( shape[m_ChannelsIndex] == 0 && channelIndex == 0) );
+        BOOST_ASSERT( heightIndex < shape[m_HeightIndex] ||
+                    ( shape[m_HeightIndex] == 0 && heightIndex == 0) );
+        BOOST_ASSERT( widthIndex < shape[m_WidthIndex] ||
+                    ( shape[m_WidthIndex] == 0 && widthIndex == 0) );
+
+        // Offset the given indices appropriately depending on the data layout
+        switch (m_DataLayout)
+        {
+        case armnn::DataLayout::NHWC:
+            batchIndex  *= shape[1] * shape[2] * shape[3]; // batchIndex *= heightIndex * widthIndex * channelIndex
+            heightIndex *= shape[m_WidthIndex] * shape[m_ChannelsIndex];
+            widthIndex  *= shape[m_ChannelsIndex];
+            // channelIndex stays unchanged
+            break;
+        case armnn::DataLayout::NCHW:
+        default:
+            batchIndex   *= shape[1] * shape[2] * shape[3]; // batchIndex *= heightIndex * widthIndex * channelIndex
+            channelIndex *= shape[m_HeightIndex] * shape[m_WidthIndex];
+            heightIndex  *= shape[m_WidthIndex];
+            // widthIndex stays unchanged
+            break;
+        }
+
+        // Get the value using the correct offset
+        return batchIndex + channelIndex + heightIndex + widthIndex;
+    }
 
 private:
     armnn::DataLayout m_DataLayout;
-- 
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