A Hybrid MPI–OpenMP Parallel Algorithm and Performance Analysis for an Ensemble Square Root Filter Designed for Multiscale Observations

2013 ◽  
Vol 30 (7) ◽  
pp. 1382-1397 ◽  
Author(s):  
Yunheng Wang ◽  
Youngsun Jung ◽  
Timothy A. Supinie ◽  
Ming Xue
Keyword(s):  
Data Assimilation ◽  
Domain Decomposition ◽  
Parallel Algorithm ◽  
Shared Memory ◽  
Message Passing ◽  
Message Passing Interface ◽  
High Volume ◽  
Square Root ◽  
Fixed Amount ◽  
Square Root Filter

Abstract A hybrid parallel scheme for the ensemble square root filter (EnSRF) suitable for parallel assimilation of multiscale observations, including those from dense observational networks such as those of radar, is developed based on the domain decomposition strategy. The scheme handles internode communication through a message passing interface (MPI) and the communication within shared-memory nodes via Open Multiprocessing (OpenMP) threads. It also supports pure MPI and pure OpenMP modes. The parallel framework can accommodate high-volume remote-sensed radar (or satellite) observations as well as conventional observations that usually have larger covariance localization radii. The performance of the parallel algorithm has been tested with simulated and real radar data. The parallel program shows good scalability in pure MPI and hybrid MPI–OpenMP modes, while pure OpenMP runs exhibit limited scalability on a symmetric shared-memory system. It is found that in MPI mode, better parallel performance is achieved with domain decomposition configurations in which the leading dimension of the state variable arrays is larger, because this configuration allows for more efficient memory access. Given a fixed amount of computing resources, the hybrid parallel mode is preferred to pure MPI mode on supercomputers with nodes containing shared-memory cores. The overall performance is also affected by factors such as the cache size, memory bandwidth, and the networking topology. Tests with a real data case with a large number of radars confirm that the parallel data assimilation can be done on a multicore supercomputer with a significant speedup compared to the serial data assimilation algorithm.

The MPI and OpenMP Implementation of Parallel Algorithm for Generating Mandelbrot Set

2014 ◽  
Vol 571-572 ◽  
pp. 26-29
Author(s):  
Xiang Wei Duan ◽  
Wei Chang Shen ◽  
Jun Guo
Keyword(s):  
Parallel Algorithm ◽  
Shared Memory ◽  
Message Passing ◽  
Message Passing Interface ◽  
Algorithm Design ◽  
Performance Testing ◽  
Mandelbrot Set ◽  
The Difference ◽  
And Performance

The paper introduce the Mandelbrot Set and the message passing interface (MPI) and shared-memory (OpenMP), analyses the characteristic of algorithm design in the MPI and OpenMP environment, describes the implementation of parallel algorithm about Mandelbrot Set in the MPI environment and the OpenMP environment, conducted a series of evaluation and performance testing during the process of running, then the difference between the two system implementations is compared.

scholarly journals Model-driven optimization of coastal sea observatories through data assimilation in a finite element hydrodynamic model (SHYFEM v. 7_5_65)

2021 ◽  
Vol 14 (1) ◽  
pp. 645-659
Author(s):  
Christian Ferrarin ◽  
Marco Bajo ◽  
Georg Umgiesser
Keyword(s):  
Finite Element ◽  
Data Assimilation ◽  
Water Level ◽  
Tide Gauge ◽  
Monitoring Network ◽  
Monitoring Site ◽  
Square Root ◽  
Monitoring Networks ◽  
Lagoon Of Venice ◽  
Square Root Filter

Abstract. Monitoring networks aims at capturing the spatial and temporal variability of one or several environmental variables in a specific environment. The optimal placement of sensors in an ocean or coastal observatory should maximize the amount of collected information and minimize the development and operational costs for the whole monitoring network. In this study, the problem of the design and optimization of ocean monitoring networks is tackled throughout the implementation of data assimilation techniques in the Shallow water HYdrodynamic Finite Element Model (SHYFEM). Two data assimilation methods – nudging and ensemble square root filter – have been applied and tested in the Lagoon of Venice (Italy), where an extensive water level monitoring network exists. A total of 29 tide gauge stations were available, and the assimilation of the observations results in an improvement of the performance of the SHYFEM model, which went from an initial root mean square error (RMSE) on the water level of 5.8 cm to a final value of about 2.1 and 3.2 cm for each of the two data assimilation methods. In the monitoring network optimization procedure, by excluding just one tide gauge at a time and always the station that contributes less to the improvement of the RMSE, a minimum number of tide gauges can be found that still allow for a successful description of the water level variability. Both data assimilation methods allow identifying the number of stations and their distribution that correctly represent the state variable in the investigated system. However, the more advanced ensemble square root filter has the benefit of keeping a physically and mass-conservative solution of the governing equations, which results in a better reproduction of the hydrodynamics over the whole system. In the case of the Lagoon of Venice, we found that, with the help of a process-based and observation-driven numerical model, two-thirds of the monitoring network can be dismissed. In this way, if some of the stations must be decommissioned due to a lack of funding, an a priori choice can be made, and the importance of a single monitoring site can be evaluated. The developed procedure may also be applied to the continuous monitoring of other ocean variables, like sea temperature and salinity.

scholarly journals Model-driven optimization of coastal sea observatories through data assimilation in a finite element hydrodynamic model (SHYFEM v.7_5_65)

2020 ◽  
Author(s):  
Christian Ferrarin ◽  
Marco Bajo ◽  
Georg Umgiesser
Keyword(s):  
Finite Element ◽  
Data Assimilation ◽  
Water Level ◽  
Tide Gauge ◽  
Monitoring Network ◽  
Monitoring Site ◽  
Square Root ◽  
Monitoring Networks ◽  
Lagoon Of Venice ◽  
Square Root Filter

Abstract. Monitoring networks aims at capturing the spatial and temporal variability of one or several environmental variables in a specific environment. The optimal placement of sensors in an ocean or coastal observatory should maximize the amount of collected information and minimize the development and operational costs for the whole monitoring network. In this study, the problem of the design and optimization of ocean monitoring networks is tackled throughout the implementation of data assimilation techniques in the Shallow water Hydrodynamic Finite Element Model (SHYFEM). Two data assimilation methods – Nudging and Ensemble Square Root Filter – have been applied and tested in the Lagoon of Venice (Italy), where an extensive water level monitoring network exists. A total of 29 tide gauge stations were available and the assimilation of the observations result in an improvement of the performance of the SHYFEM model that went from an initial root mean square error (RMSE) on the water level of 5.8 cm to a final value of about 2.1 and 3.2 cm for the two data assimilation methods, respectively. In the monitoring network optimization procedure, by excluding just one tide gauge at a time, and always the station that contributes less to the improvement of the RMSE, a minimum number of tide gauges can be found that still allow for a successful description of the water level variability. Both data assimilation methods allow identifying the number of stations and their distribution that correctly represent the state variable in the investigated system. However, the more advanced Ensemble Square Root Filter has the benefit of keeping a physically and mass conservative solution of the governing equations, which results in a better reproduction of the hydrodynamics over the whole system. In the case of the Lagoon of Venice, we found that, with the help of a process-based and observation-driven numerical model, two-thirds of the monitoring network can be dismissed. In this way, if some of the stations must be decommissioned due to a lack of funding, an a-priori choice can be made, and the importance of the single monitoring site can be evaluated. The developed procedure may also be applied to the continuous monitoring of other ocean variables, like sea temperature and salinity.

scholarly journals An Ensemble Square Root Filter for the joint assimilation of surface soil moiture and leaf area index within LDAS-Monde: application over the Euro-Mediterranean region

2019 ◽  
Author(s):  
Bertrand Bonan ◽  
Clément Albergel ◽  
Yongjun Zheng ◽  
Alina Lavinia Barbu ◽  
David Fairbairn ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Data Assimilation ◽  
Leaf Area Index ◽  
Land Surface ◽  
Mediterranean Region ◽  
Surface Soil ◽  
Positive Impact ◽  
Square Root ◽  
Area Index ◽  
Square Root Filter

Abstract. This paper introduces an Ensemble Square Root Filter (EnSRF), a deterministic Ensemble Kalman Filter, to the context of assimilating jointly observations of surface soil moisture (SSM) and leaf area index (LAI) in the Land Data Assimilation System LDAS-Monde. By ingesting those satellite-derived products, LDAS-Monde constrains the Interaction between Soil, Biosphere and Atmosphere (ISBA) land surface model (LSM), coupled with the CNRM (Centre National de Recherches Météorologiques) version of the Total Runoff Integrating Pathways (CTRIP), to improve the reanalysis of land surface variables (LSVs). To evaluate its ability to produce improved LSVs reanalyses, the EnSRF is compared with the Simplified Extended Kalman, which has been routinely operated in LDAS-Monde, in a real case over the well-studied Euro-Mediterranean region at a 0.25° spatial resolution between 2008 and 2017. Both data assimilation approaches provide a positive impact on SSM and LAI estimates with respect to the model alone, putting them closer to assimilated observations. SEKF and EnSRF have a similar behaviour for LAI showing performances that are influenced by the vegetation type. For SSM, EnSRF estimates tend to be closer to observations than SEKF. The impact of assimilating SSM and LAI is also assessed on unobserved soil moisture in the other layers of soil. Unobserved control variables are updated in the EnSRF through covariances and correlations sampled from the ensemble linking them to observed control variables. In our context, a strong correlation between SSM and soil moisture in deeper soil layers is exhibited, as expected, showing seasonal patterns that vary geographically. Moderate correlation and anti-correlations are also noticed between LAI and soil moisture in spring, summer and autumn, their absolute value tending to be larger for soil moisture in root-zone areas, showing that assimilating LAI can have an influence on soil moisture. Finally an independent evaluation of both assimilation approaches is conducted using satellite estimates of evapotranspiration and gross primary production (GPP) as well as measures of river discharges from gauging stations. The EnSRF shows a systematic albeit moderate improvement for evapotranspiration and GPP and a highly positive impact on river discharges, while the SEKF exhibits a more contrasting performance.

scholarly journals A Parallel Encryption Algorithm Based on Piecewise Linear Chaotic Map

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Xizhong Wang ◽  
Deyun Chen
Keyword(s):  
Parallel Algorithm ◽  
Message Passing ◽  
Message Passing Interface ◽  
Multicore Processors ◽  
Piecewise Linear ◽  
Chaotic Map ◽  
Encryption Algorithm ◽  
Communication Model ◽  
Piecewise Linear Chaotic Map ◽  
Encryption Decryption

We introduce a parallel chaos-based encryption algorithm for taking advantage of multicore processors. The chaotic cryptosystem is generated by the piecewise linear chaotic map (PWLCM). The parallel algorithm is designed with a master/slave communication model with the Message Passing Interface (MPI). The algorithm is suitable not only for multicore processors but also for the single-processor architecture. The experimental results show that the chaos-based cryptosystem possesses good statistical properties. The parallel algorithm provides much better performance than the serial ones and would be useful to apply in encryption/decryption file with large size or multimedia.

scholarly journals Avaliação de Desempenho no Supercomputador SDumont de uma Estratégia de Decomposição de Domínio usando as Funcionalidades de Mapeamento Topológico do MPI para um Método Numérico de Escoamento de Fluidos.

2020 ◽  
Author(s):  
Stiw Herrera ◽  
Weber Ribeiro ◽  
Thiago Teixeira ◽  
André Carneiro ◽  
Frederico Cabral ◽  
...  
Keyword(s):  
Domain Decomposition ◽  
Message Passing ◽  
High Performance ◽  
Message Passing Interface ◽  
Oil And Gas ◽  
Computational Cost ◽  
Three Dimensional ◽  
Data Allocation ◽  
Performance Study ◽  
Decomposition Strategies

Oil and gas simulations need new high-performance computing techniques to deal with the large amount of data allocation and the high computational cost that we obtain from the numerical method. The domain decomposition technique (domain division technique) was applied to a three-dimensional oil reservoir, where the MPI (Message Passing Interface) allowed the creation of a uni, bi and three-dimensional topology, where a subdivision of a reservoir could be solved in each MPI process created. A performance study was developed with these domain decomposition strategies in 20 computational nodes of the SDumont Supercomputer, using a Cascade Lake architecture.

Sign in / Sign up

Export Citation Format

Share Document