Section6.10

]>
Book Contents Previous Section 6.9 How Axiom Determines What Function to Use Next Section 6.11 Piece-Wise Function Definitions Book Index

## 6.10 Compiling vs. Interpreting

When possible, Axiom completely determines the type of every object in a function, then translates the function definition to Common Lisp or to machine code (see the next section). This translation, function:compiler called compilation, happens the first time you call the function and results in a computational delay. Subsequent function calls with the same argument types use the compiled version of the code without delay.

If Axiom cannot determine the type of everything, the function may still be executed function:interpretation but interpret-code mode in interpret-code mode: each statement in the function is analyzed and executed as the control flow indicates. This process is slower than executing a compiled function, but it allows the execution of code that may involve objects whose types change.

If Axiom decides that it cannot compile the code, it issues a message stating the problem and then the following message:

We will attempt to step through and interpret the code.

This is not a time to panic. panic:avoiding Rather, it just means that what you gave to Axiom is somehow ambiguous: either it is not specific enough to be analyzed completely, or it is beyond Axiom's present interactive compilation abilities.

This function runs in interpret-code mode, but it does not compile.

varPolys(vars) ==
for var in vars repeat
output(1 :: UnivariatePolynomial(var,Integer))
Type: Void

For vars equal to ['x,'y,'z], this function displays 1 three times.

varPolys ['x,'y,'z]
Cannot compile conversion for types involving local variables.
In particular, could not compile the expression involving ::
UnivariatePolynomial(var,Integer)
AXIOM will attempt to step through and interpret the code.
1
1
1
Type: Void

The type of the argument to output changes in each iteration, so Axiom cannot compile the function. In this case, even the inner loop by itself would have a problem:

for var in ['x,'y,'z] repeat
output(1 :: UnivariatePolynomial(var,Integer))
Cannot compile conversion for types involving local variables.
In particular, could not compile the expression involving ::
UnivariatePolynomial(var,Integer)
AXIOM will attempt to step through and interpret the code.
1
1
1
Type: Void

Sometimes you can help a function to compile by using an extra conversion or by using pretend. pretend See ugTypesSubdomains for details.

When a function is compilable, you have the choice of whether it is compiled to Common Lisp and then interpreted by the Common Lisp interpreter or then further compiled from Common Lisp to machine code. machine code The option is controlled via )set functions compile. set function compile Issue )set functions compile on to compile all the way to machine code. With the default setting )set functions compile off, Axiom has its Common Lisp code interpreted because the overhead of further compilation is larger than the run-time of most of the functions our users have defined. You may find that selectively turning this option on and off will performance give you the best performance in your particular application. For example, if you are writing functions for graphics applications where hundreds of points are being computed, it is almost certainly true that you will get the best performance by issuing )set functions compile on.

Book Contents Previous Section 6.9 How Axiom Determines What Function to Use Next Section 6.11 Piece-Wise Function Definitions Book Index