If code cannot be compiled fall back to using the interpreter (slow, but at least you always get an answer).Compile code that would most benefit from speedup (loops, functions). Here's the current approach that FreeMat takes is: For such a code we can generate very fast machine code. In most cases variables have well defined type at runtime. However, code like the snippet above is rare. However, such implementation results in code that is not much faster than interpreted code. One can imagine using an object to represent variables (the object would carry a type and pointer to memory where data is stored) and assignement operator which would assign both value and type. What's the type of a? Compiler has to know the variable size and type to emit correct code. The main reason is that the variable types are determined at runtime. This is very tricky for dynamic languages such as Matlab (also Python, Perl, etc. The goal for using JIT (just-in-time compilation) is to speed up interpreted code by compiling it in run time. However, this is 21st century and we have better ways. The old view - almost always using clever indexing one can avoid loops. Matrix or index operations on the other hand turn into internal function calls and are fast. The main reason is that I got conditioned (like the generations of matlab users) that loops are really slow because they have to be interpreted. I started using Matlab circa version 4 and I still cringe every time I have to write a loop in Matlab.
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