1. A non-transitory computer accessible memory medium that stores program instructions executable by a processor to: display a graphical data flow program in response to user input, wherein the graphical data flow program comprises a plurality of interconnected nodes that visually indicate functionality of the graphical data flow program, wherein the graphical data flow program comprises a graphical indicator that specifies to a compiler that the compiler is to attempt to automatically generate data flow program code that parallelizes a specified portion of the graphical data flow program for concurrent execution; if the specified portion is determined to be parallelizable, automatically generate the program code implementing a plurality of data flow program portions based on the graphical indicator, wherein each of the data flow program portions is configured to implement a respective part of the functionality of the specified portion of the graphical data flow program wherein during execution of the graphical data flow program, the plurality of data flow program portions execute to provide the functionality of the specified portion, wherein at least two of the plurality of data flow program portions execute concurrently, and wherein execution of the plurality of data flow program portions is functionally equivalent to execution of the specified portion of the graphical data flow program; and if the specified portion is determined to not be parallelizable, modify the appearance of the graphical indicator to indicate that the specified portion of the graphical data flow program is not parallelizable.