Re: Template Emulation?
On Apr 11, 12:53 pm, christoph.ort...@comlab.ox.ac.uk wrote:
Hi everyone,
I have some performance critical code and was wondering whether there is
some way to emulate C++ templates in order to tell the Java compiler to
optimize it somehow.
The following is a much simplified example, but the principle is the
same. Consider a class
class Vec {
public Vec(int dim) {
this.dim = dim;
this.x = new double[dim];
}
private int dim;
public double x[];
public void axpy(double alpha, Vec b) {
for (int i = 0; i < dim; i++)
this.x[i] += alpha * b.x[i];
}
}
Suppose now that the dimension is defined once in the program (possibly
as a static final variable) and then all instances of Vec have the same
dimension (say dim = 3). In this case, there should be some way for the
compiler to understand this, and unroll and inline the axpy() function.
Is there any way to achieve this in Java?
What if I declared dim as static final in the class Vec? If I would
hard-code the dimension so-to-speak?
Many thanks,
Christoph
Are you sure the particular snippet you are optimizing is really as
performance critical as you believe? Often the only way to determine
this is by using a profiler. The only way to use a profiler is to run
working code. The only way to run working code is to have written
working code.
I suggest you work on creating a well-designed working project before
you decide to complicate your design to optimize an unprofiled
application. The laws of profiling are: 1. Don't do it, and 2. (For
experts only) Don't do it yet.
Follow these laws and your life will be *so* much easier. Let the
profiler tell you whats slow, not your gut.
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