For a program that is made up of functions in units, each function is divided into instruction code blocks having a size CS where CS is the instruction cache line size of a target processor and an instruction code block that is Xth counting from the top of each function F is expressed as (F, X). Flow information of nodes that take (F, X) as identification names is extracted from an executable file of the function program. For each identification name, as neighborhood weight of each identification name that differs from that identification name, information for which that the frequency of appearance of each identification name is taken into consideration that belongs to a function that differs from that function in the neighborhood of each appearing node in the flow information is found. Based on said neighborhood weight information, the functions are arranged in the memory space such that the number of conflicts of said instruction cache is reduced.