1. A method comprising: independently compiling a plurality of modules of source code to generate a plurality of respective object modules comprising machine code and symbols other than machine code for providing information to a linker, different ones of the object modules comprising different respective parallel threads explicitly designated by a user to be executed in parallel on a target platform, and the target platform comprising an arrangement of interconnected processors; in each of the object modules, inserting at least one of said symbols to indicate a usage of a resource of the target platform associated with the respective thread; executing the linker to perform a linking process for linking the object modules, wherein the linking process comprises assessing the symbols in conjunction with one another to determine an allocation of the threads to different processors of the arrangement in dependence on the threads' associated resource usage, and based on the assessment generating an indication relating to a usage of the resource required for execution of said threads in parallel, said indication comprising an indication of said allocation; wherein the linking process further comprises linking the object modules using said indication to generate a computer program in which said threads are to be executed in parallel on the allocated processors.