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CrayDoc Glossary

barrier
Product: Cray XMT

In code, a barrier is used after a phase. The barrier delays the streams that were executing parallel operations in the phase until all the streams from the phase reach the barrier. Once all the streams reach the barrier, the streams begin work on the next phase.

blade
Product: Cray XMT

1) A field-replaceable physical entity. A Cray XMT service blade consists of AMD Opteron sockets, memory, Cray SeaStar chips, PCI-X or PCIe cards, and a blade control processor. A Cray XMT compute blade consists of Threadstorm processors, memory, Cray SeaStar chips, and a blade control processor. 2) From a system management perspective, a logical grouping of nodes and blade control processor that monitors the nodes on that blade.

blade
Product: Cray XE series, Cray XT series

1) A field-replaceable physical entity. A service blade consists of AMD Opteron sockets, memory, Cray network application-specific integrated circuit (ASIC) chips, PCI cards, and a blade control processor. A compute blade consists of AMD Opteron sockets, memory, Cray network application-specific integrated circuit (ASIC) chips, and a blade control processor. 2) From a system management perspective, a logical grouping of nodes and blade control processor that monitors the nodes on that blade.

blade control processor
Product: Cray X2, Cray XMT, Cray XT series, Cray XE series

A microprocessor on a blade that communicates with a cabinet control processor through the HSS network to monitor and control the nodes on the blade. See also blade, L0 controller, Hardware Supervisory System (HSS).

block scheduling
Product: Cray XMT

Method of thread execution used by the compiler where contiguous blocks of loop iterations are divided equally and assigned to available streams. For example, if there are 100 loop iterations and 10 streams, the compiler assigns 10 iterations to each stream. The advantage to this method is that data in registers can be reused across adjacent iterations rather than releasing a stream after each iteration.

cabinet control processor
Product: Cray X2, Cray XE series, Cray XMT, Cray XT series

A microprocessor in the cabinet that communicates with the HSS via the HSS network to monitor and control the devices in a system cabinet. See also Hardware Supervisory System (HSS).

cage
Product: Cray XE series, Cray XT series

A chassis in a cabinet of a Cray system. See chassis.

cage
Product: Cray XMT

A chassis on a Cray XMT series system. See chassis.

central data repository (CDR)
Product: Cray XT series

Stores current system state information from the event handler. The HSS uses this information to display the system state on the System Management Workstation (SMW). See also Hardware Supervisory System (HSS).

chassis
Product: Cray X2, Cray XT5h

A blade enclosure together with power distribution and four R1 router cards. A chassis houses from one to eight blades (either compute or bridge blades). Cabinets contain chassis or router modules: a compute cabinet contains two chassis; a router cabinet has three chassis and contains a router backplane housing up to 16 router modules.

chassis
Product: Cray XE series, Cray XT series

The hardware component of a Cray cabinet that houses blades. Each cabinet contains three vertically stacked chassis, and each chassis contains eight vertically mounted blades. See also cage.

chassis
Product: Cray XMT

The hardware component of a Cray XMT cabinet that houses blades. Each cabinet contains three vertically stacked chassis, and each chassis contains eight vertically mounted blades. See also cage.

class
Product: Cray XT series, Cray XE series

A group of service nodes of a particular type, such as login or I/O. See also specialization.

CLE
Product: Cray XT series, Cray XE series, Cray X2

The operating system for Cray XE and Cray XT systems.

CNL
Product: Cray XT series, Cray XE series, Cray X2

The CLE compute node kernel. CNL provides a set of supported system calls. CNL provides many of the operating system functions available through the service nodes, although some functionality has been removed to improve performance and reduce memory usage by the system.

compute blade
Product: Cray XT3

See blade.

compute node root
Product: Cray XT series

The runtime environment available to compute nodes for use in dynamic compiling, linking and execution of programs.

compute node root server
Product: Cray XT series

A Data Virtualization Services (DVS) server that projects the shared root to compute nodes for use with dynamic shared objects.

Cray DVS
Product: Cray XT series

The Cray Data Virtualization Service (Cray DVS) is a distributed network service that provides compute nodes with transparent access to file systems on the service partition using the Cray high-speed network.

Cray Fortran Compiler
Product: Cray X1 series, Cray X2

The compiler that translates Fortran source code into executable object files. The Cray Fortran Compiler supports the Fortran language through the Fortran 2003 Standard, ISO/IEC 1539-1:2004, with some exceptions and extensions, as well as selected features of the proposed Fortran 2008 Standard, as described in the Cray Fortran user documentation.

Cray RAS and Management System (CRMS)
Product:

Deprecated term: Software and hardware that implements reliability, availability, and serviceability (RAS) and some system management functions. The CRMS components use a private Ethernet network, not the system interconnection network. See also system interconnection network, Hardware Supervisory System (HSS).

Cray SeaStar chip
Product: Cray XMT

The component of the system interconnection network that provides message routing and communication services. See also system interconnection network.

Cray X2 system
Product: Cray X2

A Cray system that uses Cray X2 compute nodes for user application processing and Cray XT series service nodes for login, network, I/O, and boot functions.

deferred implementation
Product: Cray X1 series, Cray XE series, Cray XT series

The label used to introduce information about a feature that will not be implemented until a later release.

dependence analysis
Product: Cray XMT

A technique used by the compiler to determine if any iteration of a loop depends on any other iteration (this is known as a loop-carried dependency).

dynamic scheduling
Product: Cray XMT

In a dynamic schedule, the compiler does not bind iterations to streams at loop startup. Instead, streams compete for each iteration using a shared counter.

dynamic shared library
Product: Cray XE series, Cray XT series, General

See dynamic shared object.

dynamic shared object
Product: Cray XE series, Cray XT series, General

A program resource that can be linked and loaded into the address space of one or more applications at runtime.

future
Product: Cray XMT

Implements user-specified or explicit parallelism by starting new threads. A future is a sequence of code that can be executed by a newly created thread that is running concurrently with other threads in the program. Futures delay the execution of code if the code is using a value that is computed by a future, until the future completes. The thread that spawns the future uses parameters to pass information from the future to the waiting thread, which then executes. In a program, the term future is used as a type qualifier for a synchronization variable or as a keyword for a future statement.

induction variable
Product: Cray XMT

A variable that is increased or decreased by a fixed amount on each iteration of a loop.

inductive loop
Product: Cray XMT

An inductive loop is one which contains no loop-carried dependencies and has the following characteristics: a single entrance at the top of the loop; controlled by an induction variable; and has a single exit that is controlled by comparing the induction variable against an invariant.

interleaved scheduling
Product: Cray XMT

Method of executing loop iterations used by the compiler where contiguous iterations are assigned to distinct streams. For example, for a loop with 100 iterations and 10 streams, one stream performs iterations 1, 11, 21,... while another stream performs iterations 2, 12, 22, ..., and so on. This method is typically used for triangular loops because it reduces imbalances. One disadvantage to using this method is that there is loss of data reuse between loop iterations because the stream is released at the end of the iteration.

L0 controller
Product: Cray XE series, Cray XT series

See blade control processor.

L0 processor
Product: Cray XMT

See blade control processor.

L1 controller
Product: Cray XE series, Cray XT series

See cabinet control processor.

linear recurrence
Product: Cray XMT

A special type of recurrence that can be parallelized.

logical machine
Product: Cray XE series, Cray XT series

An administrator-defined portion of a physical Cray system, operating as an independent computing resource.

logical machine
Product: Cray XMT

An administrator-defined portion of a physical Cray XMT system, operating as an independent computing resource.

logical object volume (LOV)
Product: Cray XD1, Cray XT3

A grouping of (Lustre file system) OSTs that are accessed as a unit.

loop-carried dependences
Product: Cray XMT

The value from one iteration of a loop is used during a subsequent iteration of the loop. This type of loop cannot be parallelized by the compiler.

memory daughter card (MDC)
Product: Cray X2

The hardware unit containing a memory board that is pluggable on a compute module. An MDC contains one Weaver chip drive that drives 20 DDR II SDRAM memory packages, arranged as four channels of 5 packages.

metadata server (MDS)
Product: Cray XE series, Cray XT series

The component of the Lustre file system that manages Metadata Targets (MDT) and handles requests for access to file system metadata residing on those targets.

module file
Product: Cray XT series

A metafile that defines information specific to an application, a collection of applications, or a library. This term is not related to the Fortran language MODULE statement, but is related to setting up the Cray programming environment. The Modules utility uses module files to define the paths, command names, and other environment variables used by the application or library, including the version to be used. For example on Cray XT systems, to set the paths and environment variables required in order to use the default version of the Message Passing (MPI) Toolkit, enter module load xt-mpt to load the xt-mpt module file.

multicore
Product: Cascade, Cray X2, Cray XMT, Cray XT series

A processor that combines multiple independent execution engines ("cores"), each with its own cache and cache controller.

multiprocessor mode
Product: Cray XMT

A mode that can be set at compile time that ensures that when the compiled application is run, iterations of a loop are run on multiple processors.

node
Product: Cray XT series, Cray XMT, Cray XE series, Cray X2

For CLE systems, the logical group of processor(s), memory, and network components that acts as a network end point on the system interconnection network.

object storage server (OSS)
Product: Cray X2, Cray XD1, Cray XT series

The component of the Lustre file system that manages Object Storage Targets and handles I/O requests for access to file objects residing on those targets.

object storage target (OST)
Product: Cray X2, Cray XD1, Cray XT series

The Lustre system component that represents an I/O device containing file data as file system objects. This can be any LUN, RAID array, disk, disk partition, etc.

phase
Product: Cray XMT

A set of one or more sections of code that the stream executes in parallel. Each section contains an iteration of a loop. Phases and sections are contained in control flow code generated by the compiler to control the parallel execution of a function.

recovery window
Product: Cray XT series

The time period in which Lustre servers wait for previously connected clients to reconnect. After the recovery window, the service will be available on either the restarted primary server or the backup server.

recurrence
Product: Cray XMT

A recurrence occurs when a loop uses values computed in one iteration in subsequent iterations. These subsequent uses of the value imply loop-carried dependences and thus usually prevent parallelization. To increase parallelization, use linear recurrence.

reduction
Product: Cray XMT

A simple form of recurrence that reduces a large amount of data to a single value. It is commonly used to find the minimum and maximum elements of a vector. Although similar to a reduction, it is easier to parallelize and uses less memory.

region
Product: Cray XMT

A region is an area in code where threads are forked in order to perform a parallel operation. The region ends at the point where the threads join back together at the end of the parallel operation.

resiliency communication agent (RCA)
Product: Cray XE series, Cray XT series

A communications interface between the operating environment and the HSS. Each RCA provides an interface between the HSS and the processes running on a node and supports event notification, informational messages, information requests, and probes. See also Hardware Supervisory System (HSS).

service node
Product: Cray XMT

Performs support functions for applications and system services such as login, network, I/O, boot, and service database (SDB). Service nodes run a version of CLE.

single-processor mode
Product: Cray XMT

A mode that can be set at compile time that ensures that when the compiled application is run, iterations of a loop are run on a single processor.

System Management Workstation (SMW)
Product: Cray X2, Cray XE series, Cray XT series

The workstation that is the single point of control for system administration. See also Hardware Supervisory System (HSS).

system set
Product: Cray XE series, Cray XT series

A group of partitions on the BootRAID (boot root, boot node swap, shared root, boot image, SDB, syslog, UFS, etc.) that make a complete, bootable system.

Translation Lookaside Buffer (TLB)
Product: Cray XT series, Cray X2

A content addressable memory in the processor that contains cross-references between the virtual and real addresses of recently referenced pages of memory.