To whom it may concern,
About “Add support for extended precision floating-point numbers”
project of Google Summer of Code 2023.
My name is Sentaro Onizuka.
I emailed several days ago about my interest in this project and
received the details and related resources.
And I read the resources provided and would like to discuss the projects.
Here is what I understood based on the resource
・ I understood how the user-friendly API is implemented by looking at
what is already implemented in the Commons project (especially the Sum
class that uses the builder pattern).
・ I read David Bailey's paper on the QD library and understood its
algorithms. I also briefly looked over its C++ implementation.
・ I read the DD class[2] and understood the double-double
implementation and API.
What I would like to discuss is the API for a double-double. In
particular, how I can extend it to a more user-friendly API.
I have two ideas on this.
・ In the DD class API, simplify adding multiple DD values.
e.g., compute the sum a1 + a2 + a3 (ai = {ai_h, ai_l}, ai == ai_h + ai_l)
In the current DD class
DD dd = DD.create(a1[0], a1[1]);
dd = DD.add(dd.hi(),dd.lo(), a2[0], a2[1], dd);
dd = DD.add(dd.hi(),dd.lo(), a3[0], a3[1], dd);
double result = dd.doubleValue();
In contrast, we implement the varargs factory method, which allows
writing the following.
double a = {a1, a2, a3};
double result = DD.of(a).doubleValue();
The implementation is assumed to be as follows, referring to the Sum class.
public static DD of(double[][] values){
return create().add(values);
}
public DD add(final double[][] terms) {
for (double[] t : terms) {
assert i.length == 2 : “ERROR”;
add(t[0], t[1]);
}
return this;
}
public DD add(double x, double xx){
// Adds a single term to this DD.
return this;
}
・ Implement QD as well as DD. As briefly mentioned in the David Bailey
paper, for many applications, the use of DD or QD is sufficient.
Therefore, I do not think implementing arbitrary-length floating-point
numbers is necessary.
And my question is, what specific extensions do you think are needed
regarding the existing double-double API?
Also, how about my ideas on extending the API to be more
user-friendly? Am I on the right way?
Regards,
Sentaro Onizuka
[1] commons-numbers-core/src/main/java/org/apache/commons/numbers/core/Sum.java
[2]
commons-statistics-inference/src/main/java/org/apache/commons/statistics/inference/DD.java
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