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Data touching

Data touching

A <message_spec> described as being WITH DATA TOUCHING will force every word in a message to be both read and written (“touched”). When <message_spec> describes an outgoing message, the data will be touched before transmission. When <message_spec> describes an incoming message, the data will be touched after reception. In a sense, WITH DATA TOUCHING presents a more realistic assessment of network performance, as real applications almost always access the data they send or receive. It also distinguishes between messaging layers that implicitly touch data and those that can transmit data without having to touch it. One would expect the latter to perform better when the data is not touched, as the former may be paying a penalty for touching the data. However, either could perform better when messages are sent WITH DATA TOUCHING, because the latter now has to pay the penalty that the former has already paid.

Another form of data-touching supported by coNCePTuaL is WITH VERIFICATION. This causes the source task to write known, but randomly generated, data into the message before transmission and the target task to verify that every bit was correctly received. When a message is received WITH VERIFICATION, the bit_errors variable (see Predeclared variables) is updated appropriately.

WITHOUT DATA TOUCHING and WITHOUT VERIFICATION are synonymous. Both explicitly specify the default behavior of neither touching nor verifying message contents.

Scott Pakin,