FTApprox: A Fault-Tolerant Approximate Arithmetic Computing Data Format

Approximate computing (AC) is an effective energy-efficient method for error-resilient applications. The essence behind AC is to reduce energy consumption by slightly sacrificing computation accuracy purposefully while providing quality-acceptable results. On the other hand, soft error is a common problem during program execution and may cause unacceptable outputs or catastrophic failure to the system. As AC introduces errors and soft errors are mitigated by fault-tolerant mechanisms, they have conflict goals and contradictory approaches. To the best of our knowledge, there is no previous efforts to consider the two at the same time. In this paper, we study the problem of AC with soft errors in order to guarantee the safe execution of the program while reducing energy (by AC). More specifically, we propose FTApprox, a fault-tolerant approximate arithmetic computing data format, to enable the detection and correction of SEs. As an approximate data format, FTApprox can use 16 bits to approximate any 32-bit integers and fixed-point numbers, and will select only the most significant part of operands for AC at runtime. Energy saving is obtained by converting 32-bit arithmetic operations to 8-bit operations. Meanwhile, for soft errors such as random bit flips, FTApprox not only can detect all single bit flips and most 2-bit flips, it can also correct most of these errors. The experimental results show that FTApprox has significant resistance against soft errors while providing 66.4%-79.6% energy saving.