Abstract: In a distributed computing environment that includes compute nodes, where the compute nodes execute a plurality of tasks, a lock for resources may be administered. Administering the lock may be carried out by requesting, in an atomic operation by a requesting task, the lock, including: determining, by the requesting task, whether the lock is available; if the lock is available, obtaining the lock; and if the lock is unavailable, joining, by the requesting task, a queue of tasks waiting for availability of the lock.

Abstract: Methods, apparatuses, and computer program products for performing collective operations on a hybrid distributed processing system including: determining by at least one task that a parent of the task has failed to send the task data through the tree topology; and determining whether to request the data from a grandparent of the task or a peer of the task in the same tier in the tree topology; and if the task requests the data from the grandparent, requesting the data and receiving the data from the grandparent of the task through the second networking topology; and if the task requests the data from a peer of the task in the same tier in the tree, requesting the data and receiving the data from a peer of the task through the second networking topology.

Abstract: In a distributed computing environment that includes compute nodes, where the compute nodes execute a plurality of tasks, a lock for resources may be administered. Administering the lock may be carried out by requesting, in an atomic operation by a requesting task, the lock, including: determining, by the requesting task, whether the lock is available; if the lock is available, obtaining the lock; and if the lock is unavailable, joining, by the requesting task, a queue of tasks waiting for availability of the lock.

Abstract: Methods, apparatus, and products are disclosed for thread selection during context switching on a plurality of compute nodes that includes: executing, by a compute node, an application using a plurality of threads of execution, including executing one or more of the threads of execution; selecting, by the compute node from a plurality of available threads of execution for the application, a next thread of execution in dependence upon power characteristics for each of the available threads; determining, by the compute node, whether criteria for a thread context switch are satisfied; and performing, by the compute node, the thread context switch if the criteria for a thread context switch are satisfied, including executing the next thread of execution.

Abstract: Methods, apparatuses, and computer program products for collective operation management in a parallel computer are provided. Embodiments include a parallel computer having a first compute node operatively coupled for data communications over a tree data communications network with a plurality of child compute nodes. Embodiments also include each child compute node performing a first collective operation. The first compute rode, for each child compute node, receives from the child compute node, a result of the first collective operation performed by the child compute node. For each result received from a child compute node, the first compute node stores a timestamp indicating a time that the child compute node completed the first collective operation. The first compute node also manages, based on the stored timestamps, execution of a second collective operation over the tree data communications network.

Abstract: Performing a global barrier operation in a parallel computer that includes compute nodes coupled for data communications, where each compute node executes tasks, with one task on each compute node designated as a master task, including: for each task on each compute node until all master tasks have joined a global barrier: determining whether the task is a master task; if the task is not a master task, joining a single local barrier; if the task is a master task, joining the global barrier and the single local barrier only after all other tasks on the compute node have joined the single local barrier.

Abstract: Adjusting environmental variables in an adaptive parameter adjustment runtime environment, including: executing a parallel program by the adaptive parameter adjustment runtime environment, including beginning operations with a set of default global parameter values; maintaining a list of configurable parameters; changing a parameter value for a parameter in the list of configurable parameters; determining whether an effect of changing the parameter value is positive, negative, or neutral; responsive to determining that the effect of changing the parameter value is positive, changing the parameter value for the parameter; responsive to determining that the effect of changing the parameter value is negative, changing the parameter value for the parameter to a previous value; and responsive to determining that the effect of changing the parameter value is neutral, performing a list management operation on the list of configurable parameters.

Abstract: Sending, by a node requesting information regarding a resource to one or more nodes in a distributed computing system, an active message to perform a collective operation; contributing, by each node not having a resource, a value of zero to the collective operation; contributing, by a node having the resource, the node's rank; storing the result of the collective operation in a buffer of the requesting node; and identifying, in dependence upon the result of the collective operation, the rank of the node having the resource.

Abstract: Optimizing collective operations including receiving an instruction to perform a collective operation type; selecting an optimized collective operation for the collective operation type; performing the selected optimized collective operation; determining whether a resource needed by the one or more nodes to perform the collective operation is not available; if a resource needed by the one or more nodes to perform the collective operation is not available: notifying the other nodes that the resource is not available; selecting a next optimized collective operation; and performing the next optimized collective operation.

Abstract: Terminating an accelerator application program in a hybrid computing environment that includes a host computer having a host computer architecture and an accelerator having an accelerator architecture, where the host computer and the accelerator are adapted to one another for data communications by a system level message passing module (‘SLMPM’), and terminating an accelerator application program in a hybrid computing environment includes receiving, by the SLMPM from a host application executing on the host computer, a request to terminate an accelerator application program executing on the accelerator; terminating, by the SLMPM, execution of the accelerator application program; returning, by the SLMPM to the host application, a signal indicating that execution of the accelerator application program was terminated; and performing, by the SLMPM, a cleanup of the execution environment associated with the terminated accelerator application program.

Abstract: In a parallel computer, performing a rooted-v collective operation by an operational group of compute nodes includes: identifying, in source code by a collective algorithm selection optimizing module, a gather operation followed by a rooted-v collective operation; replacing, by the collective algorithm selection optimizing module, the gather operation with an allgather operation; executing, by the compute nodes, the allgather operation; selecting, by each compute node in dependence upon results of the allgather operation, an algorithm for effecting the rooted-v collective operation; and executing, by each compute node, the rooted-v collective operation with the selected algorithm.

Abstract: Methods, parallel computers, and computer program products for broadcasting shared variable directory (SVD) information in a parallel computer are provided. Embodiments include a runtime optimizer detecting, by a runtime optimizer of the parallel computer, a change in SVD information within an SVD associated with a first thread. Embodiments also include a runtime optimizer identifying a plurality of threads requiring notification of the change in the SVD information. Embodiments also include the runtime optimizer in response to detecting the change in the SVD information, broadcasting to each thread of the identified plurality of threads, a broadcast message header and update data indicating the change in the SVD information.

Abstract: Constructing a logical tree topology in a parallel computer that includes compute nodes, where each node executes a number of tasks and at least one node executes a number of tasks different from another node includes: identifying a compute node executing a greatest number of tasks; selecting, as a global root, a task from the identified compute node, including assigning the task as a local root of the identified compute node and assigning each of the other tasks of the identified compute node as a child of the local root; selecting, from each of the other compute nodes, one task to be a local root, including assigning each task other than the local root as a child of the local root; and assigning each local root of the other compute nodes to be a child of one of the tasks of the identified compute node other than the global root.

Abstract: Creating, by a parent master process of a parent communicator, a child communicator, including configuring the child communicator with a child master process, wherein a communicator includes a collection of one or more processes executing on compute nodes of a distributed computing system; determining, by the parent master process, whether a unique identifier is available to assign to the child communicator; if a unique identifier is available to assign to the child communicator, assigning, by the parent master process, the available unique identifier to the child communicator; and if a unique identifier is not available to assign to the child communicator: retrieving, by the parent master process, an available unique identifier from a master process of another communicator in a tree of communicators and assigning the retrieved unique identifier to the child communicator.

Abstract: Methods, parallel computers, and computer program products for broadcasting shared variable directory (SVD) information in a parallel computer are provided. Embodiments include a runtime optimizer detecting, by a runtime optimizer of the parallel computer, a change in SVD information within an SVD associated with a first thread. Embodiments also include a runtime optimizer identifying a plurality of threads requiring notification of the change in the SVD information. Embodiments also include the runtime optimizer in response to detecting the change in the SVD information, broadcasting to each thread of the identified plurality of threads, a broadcast message header and update data indicating the change in the SVD information.

Abstract: Constructing a logical tree topology in a parallel computer that includes compute nodes, where each node executes a number of tasks and at least one node executes a number of tasks different from another node includes: identifying a compute node executing a greatest number of tasks; selecting, as a global root, a task from the identified compute node, including assigning the task as a local root of the identified compute node and assigning each of the other tasks of the identified compute node as a child of the local root; selecting, from each of the other compute nodes, one task to be a local root, including assigning each task other than the local root as a child of the local root; and assigning each local root of the other compute nodes to be a child of one of the tasks of the identified compute node other than the global root.

Abstract: Validating a cabling topology in a distributed computing system comprised of cabled nodes connected using data communications cables, each cabled node characterized by cabling dimensions, each cable corresponding to one of the cabling dimensions, includes: receiving a selection from a user of at least one cabled node for topology validation; identifying, for each cabling dimension for each selected cabled node, a shortest cabling path; determining, for each cabling dimension, whether the number of cabled nodes in the shortest cabling path for each selected cabled node match; and if, for each cabling dimension, the number of cabled nodes in the shortest cabling path for each selected cabled node match: selecting, for each cabling dimension, the number of cabled nodes in the shortest cabling path as a representative value for the cabling dimension, calculating a product of the representative values, and determining whether the product equals the number of selected cabled nodes.

Abstract: Distributed hardware device simulation, including: identifying a plurality of hardware components of the hardware device; providing software components simulating the functionality of each hardware component, wherein the software components are installed on compute nodes of a distributed processing system; receiving, in at least one of the software components, one or more messages representing an input to the hardware component; simulating the operation of the hardware component with the software component, thereby generating an output of the software component representing the output of the hardware component; and sending, from the software component to at least one other software component, one or more messages representing the output of the hardware component.

Abstract: In a parallel computer, performing a rooted-v collective operation by an operational group of compute nodes includes: identifying, in source code by a collective algorithm selection optimizing module, a gather operation followed by a rooted-v collective operation; replacing, by the collective algorithm selection optimizing module, the gather operation with an allgather operation; executing, by the compute nodes, the allgather operation; selecting, by each compute node in dependence upon results of the allgather operation, an algorithm for effecting the rooted-v collective operation; and executing, by each compute node, the rooted-v collective operation with the selected algorithm.

Abstract: Processing data communications events in a parallel active messaging interface (‘PAMI’) of a parallel computer that includes compute nodes that execute a parallel application, with the PAMI including data communications endpoints, and the endpoints are coupled for data communications through the PAMI and through other data communications resources, including determining by an advance function that there are no actionable data communications events pending for its context, placing by the advance function its thread of execution into a wait state, waiting for a subsequent data communications event for the context; responsive to occurrence of a subsequent data communications event for the context, awakening by the thread from the wait state; and processing by the advance function the subsequent data communications event now pending for the context.