Efficient Point based Global Illumination on Intel MIC Architecture

International audiencePoint-Based Global Illumination (PBGI) is a popular rendering method in special effects and motion picture productions. The tree-cut computation is in general the most time consuming part of this algorithm, but it can be formulated for efficient parallel execution, in particular regarding wide-SIMD hardware. In this context, we propose several vectorization schemes, namely single, packet and hybrid, to maximize the utilization of modern CPU architectures. While for the single scheme, 16 nodes from the hierarchy are processed for a single receiver in parallel, the packet scheme handles one node for 16 receivers. These two schemes work well for scenes having smooth geometry and diffuse material. When the scene contains high frequency bumps maps and glossy reflections, we use a hybrid vectorization method. We conduct experiments on an Intel Many Integrated Corearchitecture and report preliminary results on several scenes, showing that up to a 3x speedup can be achieved when compared with non-vectorized execution

Study on reversal and lateral vibration in the stepped well

The reversal and lateral vibration of the drill string are very complex motion and can affect the normal operation of the drill string. The movement of the drill string in the stepped well is different from the movement of the drill string in the regular well. The vibration of the drill string in the stepped well varies with the size of the wellbore and can be visually reflected by the phase speed. To find out the relationship between reversal and lateral vibration, the natural frequency of lateral vibration of the drill string was solved by using the method of energy conservation. The analysis shows that the phase speed of flexural wave in the stepped well is faster in small size wellbore than in large size wellbore. The reversal and lateral resonance is easy to happen in small size wellbore, and the reversal will excite lateral vibration. When the sum of reversal and rotational angular frequencies approaches the natural angular frequency of lateral vibration, the lateral resonance will occur

Land-use change interacts with island biogeography to alter bird community assembly

Anthropogenic activities have reshaped biodiversity on islands worldwide. However, it remains unclear how island attributes and land-use change interactively shape multiple facets of island biodiversity through community assembly processes. To answer this, we conducted bird surveys in various land-use types (mainly forest and farmland) using transects on 34 oceanic land-bridge islands in the largest archipelago of China. We found that bird species richness increases with island area and decreases with isolation, regardless of the intensity of land-use change. However, forest-dominated habitats exhibited lower richness than farmland-dominated habitats. Island bird assemblages generally comprised species that share more similar traits or evolutionary histories (i.e., functional and/or phylogenetic clustering) than expected if assemblages were randomly assembled. Contrary to our expectations, we observed that bird assemblages in forest-dominated habitats were more clustered on large and close islands, whereas assemblages in farmland-dominated habitats were more clustered on small islands. These contrasting results indicate that land-use change interacts with island biogeography to alter the community assembly of birds on inhabited islands. Our findings emphasize the importance of incorporating human-modified habitats when examining the community assembly of island biota, and further suggest that agricultural landscapes on large islands may play essential roles in protecting countryside island biodiversity

Land-use change interacts with island biogeography to alter bird community assembly

Anthropogenic activities have reshaped biodiversity on islands worldwide. However, it remains unclear how island attributes and land-use change interactively shape multiple facets of island biodiversity through community assembly processes. To answer this, we conducted bird surveys in various land-use types (mainly forest and farmland) using transects on 34 oceanic land-bridge islands in the largest archipelago of China. We found that bird species richness increases with island area and decreases with isolation, regardless of the intensity of land-use change. However, forest-dominated habitats exhibited lower richness than farmland-dominated habitats. Island bird assemblages generally comprised species that share more similar traits or evolutionary histories (i.e., functional and/or phylogenetic clustering) than expected if assemblages were randomly assembled. Contrary to our expectations, we observed that bird assemblages in forest-dominated habitats were more clustered on large and close islands, whereas assemblages in farmland-dominated habitats were more clustered on small islands. These contrasting results indicate that land-use change interacts with island biogeography to alter the community assembly of birds on inhabited islands. Our findings emphasize the importance of incorporating human-modified habitats when examining the community assembly of island biota, and further suggest that agricultural landscapes on large islands may play essential roles in protecting countryside island biodiversity

RAPIQUE: Rapid and Accurate Video Quality Prediction of User Generated Content

Blind or no-reference video quality assessment of user-generated content (UGC) has become a trending, challenging, heretofore unsolved problem. Accurate and efficient video quality predictors suitable for this content are thus in great demand to achieve more intelligent analysis and processing of UGC videos. Previous studies have shown that natural scene statistics and deep learning features are both sufficient to capture spatial distortions, which contribute to a significant aspect of UGC video quality issues. However, these models are either incapable or inefficient for predicting the quality of complex and diverse UGC videos in practical applications. Here we introduce an effective and efficient video quality model for UGC content, which we dub the Rapid and Accurate Video Quality Evaluator (RAPIQUE), which we show performs comparably to state-of-the-art (SOTA) models but with orders-of-magnitude faster runtime. RAPIQUE combines and leverages the advantages of both quality-aware scene statistics features and semantics-aware deep convolutional features, allowing us to design the first general and efficient spatial and temporal (space-time) bandpass statistics model for video quality modeling. Our experimental results on recent large-scale UGC video quality databases show that RAPIQUE delivers top performances on all the datasets at a considerably lower computational expense. We hope this work promotes and inspires further efforts towards practical modeling of video quality problems for potential real-time and low-latency applications. To promote public usage, an implementation of RAPIQUE has been made freely available online: \url{https://github.com/vztu/RAPIQUE}.Comment: IEEE Open Journal of Signal Processing 202

An Improved Finite Control Set Model Predictive Current Control for a Two-Phase Hybrid Stepper Motor Fed by a Three-Phase VSI

In this paper, an improved finite control set model predictive current control (FCS-MPCC) is proposed for a two-phase hybrid stepper motor fed by a three-phase voltage source inverter (VSI). The conventional FCS-MPCC selects an optimal voltage vector (VV) from six active and one null VVs by evaluating a simple cost function and then applies the optimal VV directly to the VSI. Though the implementation is simple, it features a large current ripple and total harmonic distortion (THD). The proposed improved FCS-MPCC builds an extended control set consisting of 37 VVs to replace the original control set with only seven VVs. The increase in the amount of VVs helps to regulate the current more accurately. In each control period, the improved FCS-MPCC takes advantage of deadbeat control to calculate a reference VV, and only the three VVs adjacent to the reference VV are predicted and evaluated, which decrease the computational workload significantly. Build waveform patterns for all VVs in the unbalanced circuit structure to modulate the optimal VV using discrete space vector modulation, which improves the current quality in reducing current ripple and THD. The comparative simulations and experimental results validate the effectiveness of the proposed method

An Improved Finite Control Set Model Predictive Current Control for a Two-Phase Hybrid Stepper Motor Fed by a Three-Phase VSI

In this paper, an improved finite control set model predictive current control (FCS-MPCC) is proposed for a two-phase hybrid stepper motor fed by a three-phase voltage source inverter (VSI). The conventional FCS-MPCC selects an optimal voltage vector (VV) from six active and one null VVs by evaluating a simple cost function and then applies the optimal VV directly to the VSI. Though the implementation is simple, it features a large current ripple and total harmonic distortion (THD). The proposed improved FCS-MPCC builds an extended control set consisting of 37 VVs to replace the original control set with only seven VVs. The increase in the amount of VVs helps to regulate the current more accurately. In each control period, the improved FCS-MPCC takes advantage of deadbeat control to calculate a reference VV, and only the three VVs adjacent to the reference VV are predicted and evaluated, which decrease the computational workload significantly. Build waveform patterns for all VVs in the unbalanced circuit structure to modulate the optimal VV using discrete space vector modulation, which improves the current quality in reducing current ripple and THD. The comparative simulations and experimental results validate the effectiveness of the proposed method