DNN Layer Mantissa Bit Selection for Low-Power Hardware
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Solution Overview
Problem
Existing hardware implementations of Deep Neural Networks (DNNs) face challenges in terms of resource efficiency, particularly in terms of silicon area and processing power, and lack flexibility to support various DNN configurations.
Innovation Solution
A hierarchical method for selecting fixed point number formats with reduced mantissa bit lengths is applied to DNN layers, iteratively reducing mantissa bit lengths within subsets while monitoring output error, forming disjoint subsets as needed to maintain accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If fixed point number formats with reduced mantissa bit lengths are used, then power consumption and memory size are reduced, but DNN output accuracy deteriorates
Solution Approach 1:
The patent applies parameter changes by systematically varying the mantissa bit length parameter across different DNN layers. The method iteratively adjusts the mantissa bit length from an initial value downward, evaluating the impact on output accuracy at each step, and selects the maximum reduction that maintains accuracy within the threshold. This parameter optimization approach resolves the contradiction by finding the optimal balance between reduced bit length (lower power consumption) and maintained accuracy.
2Device complexity
If uniform fixed point number formats are used across all layers, then hardware implementation is simplified, but resource efficiency deteriorates due to unnecessary precision in some layers
Solution Approach 1:
The patent applies local quality by assigning different mantissa bit lengths to different DNN layers based on their specific requirements. Rather than using a uniform format across all layers, the method determines the optimal mantissa bit length for each layer individually through iterative evaluation, allowing layers that can tolerate lower precision to use fewer bits while maintaining overall accuracy. This resolves the contradiction by optimizing resource efficiency locally in each layer while maintaining acceptable global performance.
3Loss of energy
If iterative reduction of mantissa bit length is performed on all layers simultaneously, then resource efficiency is maximized, but computational complexity and time increase
Solution Approach 1:
The patent applies segmentation by dividing the DNN layers into multiple subsets and performing iterative mantissa bit length reduction on each subset separately rather than all layers simultaneously. The method processes subsets sequentially, evaluating accuracy impact and determining optimal bit lengths for each subset independently. This segmentation approach reduces the computational burden and time required compared to evaluating all layers together, while still achieving overall resource optimization.
Data Source
AI summary
Hierarchical methods for selecting fixed point number formats with reduced mantissa bit lengths for representing values input to, and/or output, from, the layers of a DNN. The methods begin with one or more initial fixed point number formats for each layer. The layers are divided into subsets of layers and the mantissa bit lengths of the fixed point number formats are iteratively reduced from the initial fixed point number formats on a per subset basis. If a reduction causes the output error of the DNN to exceed an error threshold, then the reduction is discarded, and no more reductions are made to the layers of the subset. Otherwise a further reduction is made to the fixed point number formats for the layers in that subset. Once no further reductions can be made to any of the subsets the method is repeated for continually increasing numbers of subsets until a predetermined number of layers per subset is achieved.


