Sphinx retains a somewhat cumbersome output mechanism from SKaMPI. In particular, Sphinx can generate output to four different places: an output file, a log file, stdout and stderr. The stream to stdout comprises only simple informational messages; generally it can be redirected to /dev/null without consequence. The stream to stderr includes any error messages, in addition to some informational messages; since most of the errors are also directed to the log file, it can also be redirected to /dev/null without consequence in MOST cases (no promise that all error messages are duplicated). The log file also includes mostly informational messages. It is used for the restart mechanism, which can be very useful when tests are run through a batch system.
The output file is the most interesting of the Sphinx output streams. It is divided into two sections. The first section contains a summary of the default parameters, a listing of several of the text input modes and (often most importantly) a dump of the environment pointer. The second section contains the output records corresponding to the test descriptions in the input file. These output records again are divided into two sections. The first section contains a summary of the test description. The second section contains the results for the data points specified by the test description (run-time settings, such as number of MPI tasks also affect data point selection). Each line of this section is an output result; the first n fields are the independent variable values, the next field is the test timing result in microseconds. The timing result is followed by the number of timings, the standard deviation of the timings that produced the result and then any informational flags for the timing set, such as UNSETTLED, which indicates that the standard deviation of the timings did not achieve the cut-off percentage.
Timing results are in a per “operation” form; thus the standard deviation generally applies to the timing result times the number of iterations of the operation. In addition, results may also have been corrected for overhead, which can be significant, particularly for the accurate tests of fan-out MPI collectives.