Successive Cancellation List Polar Decoder using Log-likelihood Ratios

Successive cancellation list (SCL) decoding algorithm is a powerful method that can help polar codes achieve excellent error-correcting performance. However, the current SCL algorithm and decoders are based on likelihood or log-likelihood forms, which render high hardware complexity. In this paper, we propose a log-likelihood-ratio (LLR)-based SCL (LLR-SCL) decoding algorithm, which only needs half the computation and storage complexity than the conventional one. Then, based on the proposed algorithm, we develop low-complexity VLSI architectures for LLR-SCL decoders. Analysis results show that the proposed LLR-SCL decoder achieves 50% reduction in hardware and 98% improvement in hardware efficiency.Comment: accepted by 2014 Asilomar Conference on Signals, Systems, and Computer

Enumerating Counter-Factual Type Error Messages with an Existing Type Checker

The type error message of a standard type checker for a functional language gives only a single location as potential cause of the type error. If that location is not the cause, which often is the case, then the type error message hardly helps in locating the real cause. Here we present a method that uses a standard type checker to enumerate locations that potentially cause the type error, each with an actual and a counter-factual type for the given location. Adding our method to existing compilers requires only limited effort but improves type error debugging substantially

Effects of Knowledge Base Quality on Peer-to-peer Information Propagation

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