Abstract: In one embodiment, a system includes a database operative to maintain a social graph of an online social network, a leader cache layer, a plurality of servers, and a follower cache layer comprising one or more follower cache clusters, where each follower cache cluster maintains at least a portion of the social graph, and where the follower cache layer is operative to receive a command from the servers with instructions for updating a portion of the social graph, send the command to one of the leader cache layers, receive an acknowledgment of the command from one of the leader cache layers and a request to update; and update one or more of the follower cache clusters storing the portion of the social graph associated with the command.

Abstract: An amplification system includes a differential output circuit that provides an amplified output to drive a load. A main amplifier is coupled to a terminal of the differential output circuit via a main path, corresponding to a transmission line. A peak amplifier is coupled to another terminal of the differential output circuit via a peak path, corresponding to a transmission line. In a single-ended mode while the peak amplifier is deactivated for amplification purposes, the peak path performs an impedance inversion to effectively ground the other terminal of the differential output circuit. In a differential mode, each of the peak amplifier and the main amplifier operates to conduct current to respective terminals of the differential output circuit and each of the main path and the peak path provides a predetermined output impedance to the differential output circuit.

Abstract: An amplification system includes a differential output circuit that provides an amplified output to drive a load. A main amplifier is coupled to a terminal of the differential output circuit via a main path, corresponding to a transmission line. A peak amplifier is coupled to another terminal of the differential output circuit via a peak path, corresponding to a transmission line. In a single-ended mode while the peak amplifier is deactivated for amplification purposes, the peak path performs an impedance inversion to effectively ground the other terminal of the differential output circuit. In a differential mode, each of the peak amplifier and the main amplifier operates to conduct current to respective terminals of the differential output circuit and each of the main path and the peak path provides a predetermined output impedance to the differential output circuit.

Abstract: In one embodiment, a system includes a database operative to maintain a social graph of an online social network, a leader cache layer, a plurality of servers, and a follower cache layer comprising one or more follower cache clusters, where each follower cache cluster maintains at least a portion of the social graph, and where the follower cache layer is operative to receive a command from the servers with instructions for updating a portion of the social graph, send the command to one of the leader cache layers, receive an acknowledgment of the command from one of the leader cache layers and a request to update; and update one or more of the follower cache clusters storing the portion of the social graph associated with the command.

Abstract: In one embodiment, a system includes a database; and a cache layer comprising one or more leader cache nodes, the one or more leader cache nodes operative to: communicate graph information between a follower cache layer and the database; receive a request from one of the follower cache nodes to store graph information in the database; update the database storing the graph responsive to the request; and update one or more of the follower cache nodes storing the portion of the graph associated with the request.

Abstract: In one embodiment, a system comprises a database operative to maintain a social graph, a leader cache layer comprising one or more leader cache clusters, and a follower cache layer comprising one or more follower cache clusters, wherein the leader cache layer is operative to, communicate social graph information between the follower cache cluster and the database, wherein each follower cache cluster maintains at least a portion of the social graph, receive a request from one of the follower cache clusters to store social graph information in the database, update the database storing the social graph responsive to the request, and update one or more of the follower cache clusters storing the portion of the social graph associated with the request.

Abstract: In one embodiment, a system includes a database; and a cache layer comprising one or more leader cache nodes, the one or more leader cache nodes operative to: communicate graph information between a follower cache layer and the database; receive a request from one of the follower cache nodes to store graph information in the database; update the database storing the graph responsive to the request; and update one or more of the follower cache nodes storing the portion of the graph associated with the request.

Abstract: In one embodiment, a system includes a database; and a cache layer comprising one or more cache nodes, the one or more cache nodes operative to: maintain in a memory one or more data structures storing association information describing associations between nodes in a graph a plurality of distributed cache clusters for storing information in the form of a graph, the graph comprising a plurality of nodes, each uniquely identified by a node identifier, and edge information indicating associations between nodes; respond to queries for associations between nodes in the graph by accessing the memory; and forward other queries to the database for processing.

Abstract: In one embodiment, a system comprises a database operative to maintain a social graph, a leader cache layer comprising one or more leader cache clusters, and a follower cache layer comprising one or more follower cache clusters, wherein the leader cache layer is operative to, communicate social graph information between the follower cache cluster and the database, wherein each follower cache cluster maintains at least a portion of the social graph, receive a request from one of the follower cache clusters to store social graph information in the database, update the database storing the social graph responsive to the request, and update one or more of the follower cache clusters storing the portion of the social graph associated with the request.

Abstract: A broadband high efficiency (RF) radio frequency amplifier architecture is disclosed. Systems and methods are provided for generating an amplified radio frequency (RF) signal representing a baseband input signal. First, second, and third signal paths are configured to amplify first, second, and third intermediate signals to provide respective amplified signals. A signal combiner assembly is configured to combine the amplified signals to produce the compound amplified RF signal. The signals are combined such that a first amplified signal modulates a load impedance at respective outputs of an active device associated with the plurality of amplifiers in the second signal path, and one of the first amplified signal, the second amplified signal, and a sum of the first and second amplified signals modulates a load impedance of an active device associated with the plurality of amplifiers in the third signal path.

Abstract: In one embodiment, a system includes a database operative to maintain a social graph; and a cache layer comprising a plurality of data shards, the data shards being divided among a plurality of cache nodes of a cache layer, wherein each data shard is operative to: maintain at least a portion of the social graph; receive a request to store associations between a first graph node and a second graph node of the social graph, wherein the first and second graph nodes are identified by a first and second unique identifier, respectively, the first and second graph nodes each corresponding to a particular data shard of the plurality of data shards; and update, responsive to the request, the data shard corresponding to the first graph node and the data shard corresponding to the second graph node.

Abstract: A broadband high efficiency (RF) radio frequency amplifier architecture is disclosed. Systems and methods are provided for generating an amplified radio frequency (RF) signal representing a baseband input signal. First, second, and third signal paths are configured to amplify first, second, and third intermediate signals to provide respective amplified signals. A signal combiner assembly is configured to combine the amplified signals to produce the compound amplified RF signal. The signals are combined such that a first amplified signal modulates a load impedance at respective outputs of an active device associated with the plurality of amplifiers in the second signal path, and one of the first amplified signal, the second amplified signal, and a sum of the first and second amplified signals modulates a load impedance of an active device associated with the plurality of amplifiers in the third signal path.

Abstract: In one embodiment, a system includes a database operative to maintain a social graph; and a cache layer comprising a plurality of data shards, the data shards being divided among a plurality of cache nodes of a cache layer, wherein each data shard is operative to: maintain at least a portion of the social graph; receive a request to store associations between a first graph node and a second graph node of the social graph, wherein the first and second graph nodes are identified by a first and second unique identifier, respectively, the first and second graph nodes each corresponding to a particular data shard of the plurality of data shards; and update, responsive to the request, the data shard corresponding to the first graph node and the data shard corresponding to the second graph node.

Abstract: In one embodiment, a system includes a database; and a cache layer comprising one or more cache nodes, the one or more cache nodes operative to: maintain in a memory one or more data structures storing association information describing associations between nodes in a graph a plurality of distributed cache clusters for storing information in the form of a graph, the graph comprising a plurality of nodes, each uniquely identified by a node identifier, and edge information indicating associations between nodes; respond to queries for associations between nodes in the graph by accessing the memory; and forward other queries to the database for processing.

Abstract: Systems and methods are provided for generating a modulated radio frequency (RF) output signal representing a baseband input signal. A digitizer is configured to sample the baseband input signal and produce an N-bit binary digital signal representing a scaled linear function of the signal amplitude. An RF signal source configured to produce an RF carrier signal. N amplifier paths each include at least one amplifier configured to receive the RF carrier signal as an input and provide a corresponding output RF signal. The amplifiers associated with each of the N amplifier paths are active only when a corresponding bit of the digital signal assumes a first value. A power combiner assembly is configured to combine the outputs of the plurality of amplifier paths to deliver the modulated RF output signal.

Abstract: In one embodiment, a system includes a database; and a cache layer comprising one or more cache nodes, the one or more cache nodes operative to: maintain in a memory one or more data structures storing association information describing associations between nodes in a graph a plurality of distributed cache clusters for storing information in the form of a graph, the graph comprising a plurality of nodes, each uniquely identified by a node identifier, and edge information indicating associations between nodes; respond to queries for associations between nodes in the graph by accessing the memory; and forward other queries to the database for processing.

Abstract: A distributed caching system for storing and serving information modeled as a graph that includes nodes and edges that define associations or relationships between nodes that the edges connect in the graph.

Abstract: Systems and methods are provided for generating a modulated radio frequency (RF) output signal representing a baseband input signal. A digitizer is configured to sample the baseband input signal and produce an N-bit binary digital signal representing a scaled linear function of the signal amplitude. An RF signal source configured to produce an RF carrier signal. N amplifier paths each include at least one amplifier configured to receive the RF carrier signal as an input and provide a corresponding output RF signal. The amplifiers associated with each of the N amplifier paths are active only when a corresponding bit of the digital signal assumes a first value. A power combiner assembly is configured to combine the outputs of the plurality of amplifier paths to deliver the modulated RF output signal.

Abstract: Systems and methods are provided for producing an amplified radio frequency (RF) signal representing a baseband input signal. A first amplifier amplifies a first intermediate signal to provide a first amplified signal. Second and third amplifiers amplify a second intermediate signal to provide second and third amplified signals. A signal combiner combines the first, second, and third amplified signals to produce the amplified RF signal. An RF modulator modulates an RF carrier signal with a baseband input signal to provide the first and second intermediate signals. The RF modulator provides the first and second intermediate signals such that the first amplified signal is out-of-phase with each of the second and third amplified signals at an output of an active device within the second amplifier when the amplitude of the baseband input signal exceeds a threshold voltage and in phase when the baseband input signal is below a threshold voltage.

Abstract: A circuit for amplifying an input signal can comprise a plurality of couplers. A splitting coupler of the plurality of couplers can receive the input signal and a combining coupler of the plurality of couplers can provides an output signal. N number of amplifiers can be included in the circuit to amplify the input signal, wherein N is a non-binary integer greater than one. At least one of the plurality of couplers can comprise a hybrid coupler that has two ports terminated into substantially equal reactances.