jscl.math.polynomial.groebner.ReducedRowEchelonForm Maven / Gradle / Ivy

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package jscl.math.polynomial.groebner;

import jscl.math.Generic;
import jscl.math.polynomial.Monomial;
import jscl.math.polynomial.Polynomial;

import java.util.ArrayList;
import java.util.List;

class ReducedRowEchelonForm {
	List content = new ArrayList();

	ReducedRowEchelonForm(List list) {
		content.addAll(list);
	}

	static List compute(List list) {
		ReducedRowEchelonForm f = new ReducedRowEchelonForm(list);
		f.compute();
		return f.content;
	}

	void compute() {
		int n = content.size();
		for (int i = 0; i < n; i++) reduce(i, false);
		for (int i = n - 1; i >= 0; i--) reduce(i, true);
	}

	void reduce(int pivot, boolean direction) {
		Polynomial p = polynomial(pivot);
		content.set(pivot, p = p.normalize().freeze());
		if (p.signum() == 0) return;
		Monomial m = p.head().monomial();
		int b = direction ? 0 : pivot + 1;
		int n = direction ? pivot : content.size();
		for (int i = b; i < n; i++) {
			Polynomial q = polynomial(i);
			Generic a = q.coefficient(m);
			if (a.signum() != 0) content.set(i, q.reduce(a, p));
		}
	}

	Polynomial polynomial(int n) {
		return (Polynomial) content.get(n);
	}

	public String toString() {
		StringBuffer buffer = new StringBuffer();
		buffer.append("{");
		int n = content.size();
		for (int i = 0; i < n; i++) {
			Polynomial p = polynomial(i);
			buffer.append(i > 0 ? ", " : "").append(p);
		}
		buffer.append("}");
		return buffer.toString();
	}
}