A data processing apparatus adapted to output recommendation information for modifying source code, includes: compiler circuitry to compile the source code and to output compiled code for the source code, processing circuitry to execute the compiled code, profile circuitry to monitor the execution of the compiled code by the processing circuitry and to generate profile information for the execution of the compiled code, the profile information including one or more statistical properties for the execution of the compiled code, and recommendation circuitry to output the recommendation information for the source code, the recommendation circuitry including a machine learning model to receive at least a portion of the profile information and trained to output the recommendation information for the source code in dependence upon one or more of the statistical properties, in which the recommendation information is indicative of one or more editing instructions for modifying the source code.