298 research outputs found
Implementation of MPICH on top of MPLi̲te
The goal of this thesis is to develop a new Channel Interface device for the MPICH implementation of the MPI (Message Passing Interface) standard using MPLi̲te. MPLi̲te is a lightweight message-passing library that is not a full MPI implementation, but offers high performance. MPICH (Message Passing Interface CHameleon) is a full implementation of the MPI standard that has the p4 library as the underlying communication device for TCP/IP networks. By integrating MPLi̲te as a Channel Interface device in MPICH, a parallel programmer can utilize the full MPI implementation of MPICH as well as the high bandwidth offered by MPLi̲te. There are several layers in the MPICH library where one can tie a new device. The Channel Interface is the lowest layer that requires very few functions to add a new device. By attaching MPLi̲te to MPICH at the lowest level, the Channel Interface, almost all of the performance of the MPLi̲te library can be delivered to the applications using MPICH. MPLi̲te can be implemented either as a blocking or a non-blocking Channel Interface device. The performance was measured on two separate test clusters, the PC and the Alpha mini-clusters, having Gigabit Ethernet connections. The PC cluster has two 1.8 GHz Pentium 4 PCs and the Alpha cluster has two 500 MHz Compaq DS20 workstations. Different network interface cards like Netgear, TrendNet and SysKonnect Gigabit Ethernet cards were used for the measurements. Both the blocking and non-blocking MPICH-MPLi̲te Channel Interface devices perform close to raw TCP, whereas a performance loss of 25-30% is seen in the MPICH-p4 Channel Interface device for larger messages. The superior performance offered by the MPICH-MPLi̲te device compared to the MPICH-p4 device can be easily seen on the SysKonnect cards using jumbo frames. The throughput curve also improves considerably by increasing the Eager/Rendezvous threshold
A low-cost parallel implementation of direct numerical simulation of wall turbulence
A numerical method for the direct numerical simulation of incompressible wall
turbulence in rectangular and cylindrical geometries is presented. The
distinctive feature resides in its design being targeted towards an efficient
distributed-memory parallel computing on commodity hardware. The adopted
discretization is spectral in the two homogeneous directions; fourth-order
accurate, compact finite-difference schemes over a variable-spacing mesh in the
wall-normal direction are key to our parallel implementation. The parallel
algorithm is designed in such a way as to minimize data exchange among the
computing machines, and in particular to avoid taking a global transpose of the
data during the pseudo-spectral evaluation of the non-linear terms. The
computing machines can then be connected to each other through low-cost network
devices. The code is optimized for memory requirements, which can moreover be
subdivided among the computing nodes. The layout of a simple, dedicated and
optimized computing system based on commodity hardware is described. The
performance of the numerical method on this computing system is evaluated and
compared with that of other codes described in the literature, as well as with
that of the same code implementing a commonly employed strategy for the
pseudo-spectral calculation.Comment: To be published in J. Comp. Physic
Performance evaluation of an open distributed platform for realistic traffic generation
Network researchers have dedicated a notable part of their efforts
to the area of modeling traffic and to the implementation of efficient traffic
generators. We feel that there is a strong demand for traffic generators
capable to reproduce realistic traffic patterns according to theoretical
models and at the same time with high performance. This work presents an open
distributed platform for traffic generation that we called distributed
internet traffic generator (D-ITG), capable of producing traffic (network,
transport and application layer) at packet level and of accurately replicating
appropriate stochastic processes for both inter departure time (IDT) and
packet size (PS) random variables. We implemented two different versions of
our distributed generator. In the first one, a log server is in charge of
recording the information transmitted by senders and receivers and these
communications are based either on TCP or UDP. In the other one, senders and
receivers make use of the MPI library. In this work a complete performance
comparison among the centralized version and the two distributed versions of
D-ITG is presented
NIC-assisted cache-efficient receive stack for message passing over Ethernet
International audienceHigh-speed networking in clusters usually relies on advanced hardware features in the NICs, such as zero-copy capability. Open-MX is a high-performance message passing stack tailored for regular Ethernet hardware without such capabilities. We present the addition of a multiqueue support in the Open-MX receive stack so that all incoming packets for the same process are handled on the same core. We then introduce the idea of binding the target end process near its dedicated receive queue. This model leads to a more cache-efficient receive stack for Open-MX. It also proves that very simple and stateless hardware features may have a significant impact on message passing performance over Ethernet. The implementation of this model in a firmware reveals that it may not be as efficient as some manually tuned micro-benchmarks. But our multiqueue receive stack generally performs better than the original single queue stack, especially on large communication patterns where multiple processes are involved and manual binding is difficult
Optimized framegrabber for the Cherenkov telescope array
Our contribution presents a high bandwidth platform that implements traffic aggregation and switching
capabilities for the Cherenkov telescope array (CTA) cameras. Our proposed system integrates two different
data flows: a unidirectional one from the cameras to an external server and a second one, fully configurable
dedicated to configuration and control traffic for the camera management. The former requires high bandwidth
mechanisms to be able to aggregate several 1 gigabit Ethernet links into one high speed 10 gigabit Ethernet port.
The latter is responsible for providing routing components to allow a control and management path for all the
elements of the cameras. Hence, a simple, efficient, and flexible routing mechanism has been implemented
avoiding complex circuitry that impacts in the system performance. As a consequence, an asymmetric network
topology allows high bandwidth communication and, at the same time, a flexible and cost-effective implementation.
In our contribution, we analyze the camera requirements and present the proposed architecture.
Moreover, we have designed several evaluation tests to demonstrate that our solution fulfills the CTA project
needs. Finally, we illustrate the general possibilities of the proposed solution for other data acquisition applications
and the most promising futures lines of research are discussed.This work
has been partially funded by the Horizon 2020 (H2020)
ASTERICS (Grant No. 653477) and AYA2015-65973-C3-2-R
AMIGA6
Using XDAQ in Application Scenarios of the CMS Experiment
XDAQ is a generic data acquisition software environment that emerged from a
rich set of of use-cases encountered in the CMS experiment. They cover not the
deployment for multiple sub-detectors and the operation of different processing
and networking equipment as well as a distributed collaboration of users with
different needs. The use of the software in various application scenarios
demonstrated the viability of the approach. We discuss two applications, the
tracker local DAQ system for front-end commissioning and the muon chamber
validation system. The description is completed by a brief overview of XDAQ.Comment: Conference CHEP 2003 (Computing in High Energy and Nuclear Physics,
La Jolla, CA
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