\" @(#)intro.me 1.9 3/15/82 .sh 1 "Programs to be Profiled" .pp Software research environments normally include many large programs both for production use and for experimental investigation. These programs are typically modular, in accordance with generally accepted principles of good program design. Often they consist of numerous small routines that implement various abstractions. Sometimes such large programs are written by one programmer who has understood the requirements for these abstractions, and has programmed them appropriately. More frequently the program has had multiple authors and has evolved over time, changing the demands placed on the implementation of the abstractions without changing the implementation itself. Finally, the program may be assembled from a library of abstraction implementations unexamined by the programmer. .pp Once a large program is executable, it is often desirable to increase its speed, especially if small portions of the program are found to dominate its execution time. The purpose of the \fBgprof\fP profiling tool is to help the user evaluate alternative implementations of abstractions. We developed this tool in response to our efforts to improve a code generator we were writing [Graham82]. .pp The \fBgprof\fP design takes advantage of the fact that the programs to be measured are large, structured and hierarchical. We provide a profile in which the execution time for a set of routines that implement an abstraction is collected and charged to that abstraction. The profile can be used to compare and assess the costs of various implementations. .pp The profiler can be linked into a program without special planning by the programmer. The overhead for using \fBgprof\fP is low; both in terms of added execution time and in the volume of profiling information recorded.