This work proposes a novel multi-task and multi-fidelity autotuning framework, GPTuneBand, for tuning large-scale expensive high performance computing (HPC) applications. GPTuneBand combines a multi-task Bayesian optimization algorithm with a multi-armed bandit strategy, well-suited for tuning expensive HPC applications such as numerical libraries, scientific simulation codes and machine learning (ML) models, particularly with a very limited tuning budget. Our numerical results show that compared to other stateof-the-art autotuners, which only allows single-task or single-fidelity tuning, GPTuneBand obtains significantly better performance for numerical libraries and simulation codes, and competitive validation accuracy for training ML models. When tuning the Hypre library with 12 parameters, GPTuneBand wins over its single-fidelity predecessor GPTune on 62.5% tasks, with a maximum speedup of 1.2x, and wins over a single-task, multi-fidelity tuner BOHB on 72.5% tasks. When tuning the MFEM library on large numbers of CPU cores, GPTuneBand obtains a 1.7x speedup when compared with the default code parameters.

We present zircon U–Pb ages, major and trace element analyses and zircon Hf isotope data on the Cretaceous mafic–felsic igneous rocks in the north‐eastern North China Craton (NCC) of NE China. These data have been used to discuss the petrogenesis of the mafic–felsic igneous rocks in order to constrain the geodynamical and magmatic evolution of the region. Zircon U–Pb dating results indicate that these igneous rocks crystallized during the Cretaceous (ca. 123–90 Ma). These mafic igneous rocks display low SiO2 contents, high MgO contents and marked enrichments in large‐ion lithophile elements (LILEs) and depletions in high‐field‐strength elements (HFSEs), combined with their εHf(t) values and La/Nb versus La/Ba diagram, suggesting they were derived from lithospheric mantle that experienced gradually increasing fluid metasomatism from 123 to 90 Ma. The felsic igneous rocks with high SiO2 values are metaluminous to weakly peraluminous and belong to the high–K calc–alkaline series. These felsic igneous rocks are all enriched in light rare earth elements (LREEs) and LILEs and relatively depleted in HFSEs, with barely negative Eu anomalies, combined with their εHf(t) values, these felsic igneous rocks were derived from partial melting of a lower crust. A synthesis of these new data with previous researches shows that the subduction and rollback of the Palaeo‐Pacific slab played a major role in the destruction of the north‐eastern NCC. The diagenetic temperatures of igneous rocks indicate that the mechanism of destruction of the NCC may be heterogeneous, most likely a thermal erosion mechanism in eastern Jilin area and a delamination mechanism in Liaodong Peninsula.

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