Can Differentiable Decision Trees Learn Interpretable Reward Functions?

There is an increasing interest in learning reward functions that model human intent and human preferences. However, many frameworks use blackbox learning methods that, while expressive, are difficult to interpret. We propose and evaluate a novel approach for learning expressive and interpretable reward functions from preferences using Differentiable Decision Trees (DDTs) for both low- and high-dimensional state inputs. We explore and discuss the viability of learning interpretable reward functions using DDTs by evaluating our algorithm on Cartpole, Visual Gridworld environments, and Atari games. We provide evidence that that the tree structure of our learned reward function is useful in determining the extent to which a reward function is aligned with human preferences. We visualize the learned reward DDTs and find that they are capable of learning interpretable reward functions but that the discrete nature of the trees hurts the performance of reinforcement learning at test time. However, we also show evidence that using soft outputs (averaged over all leaf nodes) results in competitive performance when compared with larger capacity deep neural network reward functions

Comparison Of Effects Of Isobaric Levobupivacaine Versus Hyperbaric Bupivacaine In Elective Caesarean Sections In Spinal Anaesthesia : A Randomized Prospective Study

Background and Aim: The aim of this study was to compare the sensory , motor and hemodynamic effects of Isobaric levobupivacaine with fentanyl versus hyperbaric bupivacaine with fentanyl in elective caesarean sections in spinal anaesthesia and to compare the difference in time to first rescue analgesic requirement in both the groups.Methods:126 patients of ASA grade I and grade II included in this prospective, randomized, interventional study were randomly allocated into 2 groups- Group I (n=63) received Isobaric levobupivacaine 0.5 % (10 mg) 2ml + fentanyl 0.5 ml (25 mcg) and Group II (n=63) received 0.5% Hyperbaric bupivacaine (10 mg) 2ml + fentanyl 0.5 ml (25 mcg). The onset of sensory block was defined as the time taken for sensory block to reach T10 and the motor block was assessed using Bromage score and time taken to reach Bromage score 1 was defined as onset of motor block. Total duration of analgesia was assessed using VAS Scale and rescue analgesic was given at VAS score of 3 or more.Results: The demographic variables were comparable in both the groups. The onset of sensory and motor block and time taken to achieve maximum level of sensory and motor block was significantly delayed in levobupivacaine group as compared to bupivacaine group (p value < 0.001).The sensory and motor block duration was however longer in bupivacaine group as compared to levobupivacaine group (p value <0.001). The total duration of analgesia in patients of levobupivacaine group was 157.3±7.13 (minutes)and shorter than in patients of bupivacaine group ( 165.32±7.35 (minutes)). The side effects like hypotension and bradycardia occurred significantly more in patients of bupivacaine group as compared to levobupivacaine group.Conclusion: Intrathecal combination of levobupivacaine and fentanyl can be a good and safe option for caesarean section with shorter motor block and less hemodynamic side effects but with shorter duration of postoperative analgesia as compared to combination of intrathecal bupivacaine and fentanyl