Dapper (Distributed and Parallel Program Execution Runtime) is a tool for taming the complexities of developing for large-scale cloud and grid computing, enabling the user to create distributed computations from the essentials -- the code that will execute, along with a dataflow graph description.

Under the Dapper model, the user no longer needs to worry about traditionally ad-hoc aspects of managing the cloud or grid, which include handling data interconnects and dependencies, recovering from errors, distributing code, and starting jobs. Perhaps more importantly, it provides an entire Java-based toolchain and runtime for framing nearly all coarse-grained distributed computations in a consistent format that allows for rapid deployment and easy conveyance to other researchers.

Dapper Features:
1. A code distribution system that allows the Dapper server to transmit requisite program code over the network and have clients dynamically load it. A consequence of this is that, barring external executables, updates to Dapper programs need only happen on the server-side.
2. A powerful subflow embedding method for dynamically modifying the dataflow graph at runtime.
3. A runtime in vanilla Java, a language that many are no doubt familiar with. Aside from the requirement of a recent JVM and optionally Graphviz Dot, Dapper is self-contained.
4. A robust control protocol. The Dapper server expects any number of clients to fail, at any time, and has customizable re-execution and timeout policies to cope. Consequently, one can start and stop (long-lived) clients without fear of putting the entire system into an inconsistent state.
5. Flexible semantics that allow data transfers via files or TCP streams.
6. Interoperability with firewalls. Since your local cloud or grid probably sits behind a firewall, we have devised special semantics for streaming data transfers.
7. Liberal licensing terms. Dapper is released under the BSD License to prevent contamination of your codebase.
8. Operation as an embedded application. A user manual describes the programming API that users can follow to run the Dapper server inside an application like Apache Tomcat.
9. Operation as a standalone user interface. With it, one can run off-the-shelf demos and learn core concepts from visual examples. By following a minimal set of conventions, one can then bundle one's own Dapper programs as execution archives, and then get realtime dataflow status and debugging feedback.

Requirements:
* Java
* Graphviz

The license of this software is Free, you can free download and free use this calculator software.