Programming tutorials serve a crucial role in teaching coding and programming techniques. Creating high-quality programming tutorials remains a laborious task. Authors devote effort in writing step-by-step solutions, creating examples, and editing existing tutorials. We explore the potential of using the text-code connection to improve the authoring experience of programming tutorials. We proposed a mixed-initiative approach to infer, establish, and maintain the latent text-code connections. With a series of interactions, the STEP-LINK ( STEP- by-Step Tutorial Editing with Programmable LINK ages ) prototype leverages text-code connections to assist users in authoring tutorials. The results of our experiment demonstrate the effectiveness of our system in supporting users in the authoring of step-by-step code explanations, the creation of examples, and the iteration of tutorials.

Only a single example is known of a regenerating code with both small field size and efficient repair, and with parameters in a corner point on the cutset bound different from the MSR and MBR points. Here we present another such code, based on a vector space partition of a 9-dimensional binary space into 73 subspaces of dimension 3 that is strongly related to the projective plane PG(2, 8); the coding spaces of the code consist of 72 of the subspaces in the partition. The new storage code comes with an efficient repair algorithm that can be described in terms of the underlying geometry.

Pooled mining has become the most popular mining approach in the Bitcoin system, which can effectively reduce the variance of the block generation reward of participants. The security of pooled mining depends on whether it is incentive compatible, that is, an honest participant will get a reward proportional to his work. Recent attacks on mining pools, for example, Block Withholding, Fork After Withholding, and Power Adjusting Withholding (PAW) attacks, show that malicious participants may undermine the revenue of the honest pools and receive an unfair share of the mining reward. This paper shows that the security of Bitcoin is even worse than what the recent attacks demonstrated. We describe an attack called Fork Withholding Attack under a Protection Racket (FWAP), in which the mining pool pays the attacker for withholding a fork. Our insight is that the mining pools under forking attacks have incentives to pay in exchange for not being forked. The attacker and the paying pool negotiate how much to be paid, and we show that it is possible for both the attacker and the paying pool to earn higher rewards at the expense of the other pools. In particular, our formal analysis and simulation demonstrate that the payer and the FWAP attacker can get up to 1.8 × and 3.8 × of extra reward as in PAW, respectively. Furthermore, FWAP can escape from the “miners’ dilemma’’ when two FWAP attackers attack each other under some circumstances. We also propose simple approaches that serve as the first step towards preventing the FWAP attack.

Update performance is a common concern in modern distributed storage systems. In this work, we construct explicit update-efficient codes via finite projective planes, also having efficient local repair with availability, and a short description. We compare to other existing solutions, including block codes from convolutional codes.We analyze the repair behavior of the codes via analogy with decoding of LDPC codes over an erasure channel, and the performance of the distributed storage system based on the codes involving updates and repairs.