PGPROF User's Guide - The Portland Group

Data and Precision
BYTES RECEIVED
For MPI profiles only. This is the number of bytes received in a data transfer.
BYTES SENT
For MPI profiles only. This is the number of bytes sent.
CALLS
The number of times a function is called.
COST
The sum of the differences between the timer value entering and exiting a function. This
includes time spent on behalf of the current function in all children whether profiled or not.
PGPROF can provide cost information when you compile your program with either the –
Mprof=cost or the –Mprof=lines option. For more information, refer to Basic Profiling.
COUNT
The number of times a line or function is executed.
LINE NUMBER
For line mode, this is the line number for that line. For function mode, this is the line number
of the first line of the function. PGPROF sometimes generates multiple statements for a single
source line; thus multiple profiling entries might appear for a single source line. To distinguish
them, PGPROF uses the notation: lineNo.statementNo
MESSAGES
For MPI profiles only. This is the number of messages sent and received by the function or
line.
RECEIVES
For MPI profiles only. This is the number of messages received by the function or line.
SENDS
For MPI profiles only. This is the number of messages sent by the function or line.
TIME
The time spent only within the function or executing the line. The TIME does not include time
spent in functions called from this function or line. TIME may be displayed in seconds or as a
percent of the total time.
6.3. Caveats (Precision of Profiling Results)
6.3.1. Accuracy of Performance Data
The collection of performance data always introduces some overhead, or intrusion, that can affect
the behavior of the application being monitored. How this overhead affects the accuracy of the
performance data depends on the performance monitoring method chosen, system software and
hardware attributes, the load on the system during data collection, and the idiosyncrasies of the
profiled application. Although the PGPROF implementation attempts to minimize intrusion and
maximize accuracy, it would be unwise to assume the data is beyond question.
6.3.2. Clock Granularity
Many target machines provide a clock resolution of only 20 to 100 ticks per second. Under
these circumstances, a routine must consume at least a few seconds of CPU time to generate
meaningful line level times.
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