Random thoughts of a computer scientist who is working behind the enemy lines; and lately turned into a double agent. Last week, the New York Times Sunday magazine had an article titled The Reviewing Stand, starting with the following: Here’s a challenge for students of expository writing: review a popular product on Amazon and aim to get your review chosen by readers as “most helpful.” It’s dead
Key Facts The mathematical definition of a hypergraph is an extension to the standard graph concept that allows an edge to point to more than two nodes. HyperGraphDB extends this even further by allowing edges to point to other edges as well and making every node or edge carry an arbitrary value as payload. The original requirements that triggered the development of the system came from the OpenCo
With the success of Neo4j as a graph database in the NoSQL revolution, it's interesting to see another graph database, HyperGraphDB, in the mix. Their quick blurb on HyperGraphDB says it is a: general purpose, extensible, portable, distributed, embeddable, open-source data storage mechanism. It is a graph database designed specifically for artificial intelligence and semantic web projects, it can
Linux は fork で子プロセスを作成した場合、親の仮想メモリ空間の内容を子へコピーする必要があります。しかしまともに全空間をコピーしていたのでは fork のコストが高くなってしまいますし、子が親と同じようなプロセスとして動作し続ける場合は、内容の重複したページが多数できてしまい、効率がよくありません。 そこで、Linux の仮想メモリは、メモリ空間を舐めてコピーするのではなく、はじめは親子でメモリ領域を共有しておいて、書き込みがあった時点で、その書き込みのあったページだけを親子で個別に持つという仕組みでこの問題を回避します。Copy-On-Write (CoW) と呼ばれる戦略です。共有メモリページは、親子それぞれの仮想メモリ空間を同一の物理メモリにマッピングすることで実現されます。より詳しくは コピーオンライト - Wikipedia などを参照してください。 この CoW に
ElasticSearch is an open source, distributed, RESTful search engine built on top of Lucene. Its features include: Distributed and Highly Available Search Engine. Each index is fully sharded with a configurable number of shards. Each shard can have zero or more replicas. Read / Search operations performed on either replica shard. Multi Tenant with Multi Types. Support for more than one index. Suppo
It looks like the Digg guys are the most public about their usage of Cassandra. Arin’s presentation below is a bit less technical than the ☞ article published a while back, but also has some nice additions. My notes: how it is to use an alpha-stage project that you don’t have any idea how others are using the problem with sharding is that there’s no standard way to doing itif you start giving away
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