We present a denotational semantics for weak memory concurrency that avoids thin-air reads, provides data-race free programs with sequentially consistent semantics (DRF-SC), and supports a compositional refinement relation for validating optimisations. Our semantics identifies false program dependencies that might be removed by compiler optimisation, and leaves in place just the dependencies necessary to rule out thin-air reads. We show that our dependency calculation can be used to rule out thin-air reads in any axiomatic concurrency model, in particular C++. We present a tool that automatically evaluates litmus tests, show that we can augment C++ to fix the thin-air problem, and we prove that our augmentation is compatible with the previously used compilation mappings over key processor architectures. We argue that our dependency calculation offers a practical route to fixing the longstanding problem of thin-air reads in the C++ specification.

Humans are now recognized as the main drivers of environmental change, leaving the future of our planet dependent on human action or inaction. Although the outlook of our planet is often depicted in a “doom and gloom” manner due to recent troubling environmental trends, we suggest that a “good Anthropocene” (in which human quality of life may be maintained or improved without cost to the environment) is attainable if we engage in adaptive, multi-disciplinary actions capable of addressing the socio-ecological issues of today and tomorrow. Early-career conservation scientists and practitioners have an unmatched understanding of novel technologies and social connectivity and, as those left with the ever-growing responsibility to be the problem solvers of the attributed increasing environmental consequences of living in the Anthropocene, their perspectives on steps towards a good Anthropocene are valuable. Here we present a list of 20 actions derived by early-career conservation scientists and practitioners for conservationists to help achieve a good Anthropocene that utilize the social connectivity and technology of today. Central to these actions are the notions that multi-, inter-, and trans-disciplinary collaboratives that embrace diverse world views need to be integrated into decision-making processes; training and outreach platforms need to communicate both environmental challenges and solutions broadly; and conservation successes need to be acknowledged and disseminated in a forward-looking, adaptive capacity. Together the 20 actions identified here reinforce the underlying paradigm shift that must accompany living in the Anthropocene, given that biodiversity and healthy ecosystems are requisite for sustained human life. By sharing this list of actions, we look to promote positive socio-environmental changes towards the collective goal of achieving a good Anthropocene.

A key challenge when writing quantum programs is the need for uncomputation: temporary values produced during the computation must be reset to zero before they can be safely discarded. Unfortunately, most existing quantum languages require tedious manual uncomputation, often leading to inefficient and error-prone programs.We present Unqomp, the first procedure to automatically synthesize uncomputation in a given quantum circuit. Unqomp can be readily integrated into popular quantum languages, allowing the programmer to allocate and use temporary values analogously to classical computation, knowing they will be uncomputed by Unqomp.Our evaluation shows that programs leveraging Unqomp are not only shorter (-19% on average), but also generate more efficient circuits (-71% gates and -19% qubits on average).

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