Abstract: A method of reading from a storage medium to recover a group of information sectors, each comprising a respective information payload. The medium stores redundancy data comprising a plurality of separate redundancy codes for the group, each code being a linear sum of terms, each term in the sum being the information payload from a different respective one of the information sectors in the group weighted by a respective coefficient of a set of coefficients for the redundancy code. The method comprises, after the redundancy data has already been stored on the medium: identifying a set of k? information sectors to be recovered; selecting k? of the redundancy codes; determining a square matrix E of the k? information sectors by the k? sets of coefficients of the selected codes; determining a matrix D being a matrix inverse of E; and recovering the k? information payloads from the inverse matrix D.

Abstract: A switching network for effecting point-to-point communication between nodes has a time-varying switching configuration, which causes successive activation and deactivation of multiple channels of the switching network, a first of the channels connecting, when activated, a transmitter node and a first receiver node, and a second of the channels connecting, when activated, the transmitter node and a second receiver node.

Abstract: In various examples there is a communications network comprising a plurality of nodes connected via an interconnection medium to form a receive-from-many communications network. The network has a synchronisation mechanism which synchronizes a signal frequency of the nodes. The network has at least one store holding signal amplitude data of signals previously sent between specified pairs of nodes of the communications network. An amplitude controller uses the stored data to adjust amplitudes of signals communicated between at least one of the pairs of nodes of the communications network.

Abstract: A wavelength switchable laser is described which has a multi-wavelength laser source configured to generate signals at different wavelengths. The wavelength switchable laser has a wavelength selector with a plurality of electro-optical switches, each electro-optical switch being configurable to transmit or block output of one of the signals from the multi-wavelength source according to the wavelength of the signal.

Abstract: In various examples there is a communications network comprising a plurality of nodes connected via an interconnection medium to form a receive-from-many communications network. The network has a synchronisation mechanism which synchronizes a signal frequency of the nodes. The network has at least one store holding signal amplitude data of signals previously sent between specified pairs of nodes of the communications network. An amplitude controller uses the stored data to adjust amplitudes of signals communicated between at least one of the pairs of nodes of the communications network.

Abstract: In various examples a compute node is described. The compute node has a central processing unit which implements a hardware transactional memory using at least one cache of the central processing unit. The compute node has a memory in communication with the central processing unit, the memory storing information comprising at least one of: code and data. The compute node has a processor which loads at least part of the information, from the memory into the cache. The processor executes transactions using the hardware transactional memory and at least the loaded information, such that the processor ensures that the loaded information remains in the cache until completion of the execution.

Abstract: There is a communications network node comprising a transmitter or a receiver configured to communicate with a plurality of other nodes via an interconnection medium interconnecting the node and the other nodes. The node is frequency synchronized with regard to signal transmission or reception, via a frequency synchronization mechanism, with at least one of the other nodes. The node has at least one store holding phase data relating to an amount of phase asynchrony and path characteristics between the node and at least one of the other nodes. A phase controller uses the stored data to adjust phase used by the node such that the recovery of data when communicating with at least one other node is facilitated.

Abstract: In various examples a compute node is described. The compute node has a central processing unit which implements a hardware transactional memory using at least one cache of the central processing unit. The compute node has a memory in communication with the central processing unit, the memory storing information comprising at least one of: code and data. The compute node has a processor which loads at least part of the information, from the memory into the cache. The processor executes transactions using the hardware transactional memory and at least the loaded information, such that the processor ensures that the loaded information remains in the cache until completion of the execution.