A method for finding an error in a computer program is disclosed. A sequence of machine instructions performed by a processor is recorded as trace data. A mapping file is accessed. A source code instruction is translated into a machine code instruction according to a mapping found in the mapping file. Further, at least a portion of the trace data is searched through until the machine code instruction is found. In addition, a first execution time of the machine code instruction is determined by reviewing the trace data in a first vicinity that an address of the machine code instruction is located. Further, a second execution time of the next machine code instruction is determined by reviewing the trace data in a second vicinity that an address of the next machine code instruction is located. Accordingly, performance data is calculated by subtracting the first execution time from the second execution time. The performance data is displayed.