Not Supported Python Programs

HPAT statically compiles user codes to generate efficient parallel programs. Hence, the user code needs to be statically compilable. This means that HPAT should be able to infer all the variable types, and be able to analyze the computations.

Type Stability

To enable type inference, the program should be type stable, which means every variable should have a single type. The example below is not type stable since variable a can be both a float and an array of floats:

if flag:
    a = 1.0
else:
    a = np.ones(10)

The use of isinstance operator of Python often means type instabillity and is not supported.

Similarly, function calls should also be deterministic. The below example is not supported since function f is not known in advance:

if flag:
    f = np.zeros
else:
    f = np.random.ranf
A = f(10)

One can usually avoid these cases in numerical code without significant effort.