02_checkVertices.md

This is a checker method that can verify complex propeties about matrices. In the bottom part of the checker, one can observe an extraordinary double imbricated for loop that checks that the min variable correctly converges from Double.POSITIVE_INFINITY to 0 ± 10-6. (source)

    // org.apache.commons.math3.geometry.euclidean.twod.PolygonsSetTest
    private void checkVertices(Vector2D[][] rebuiltVertices,
                               Vector2D[][] vertices) {
        // each rebuilt vertex should be in a segment joining two original vertices
        for (int i = 0; i < rebuiltVertices.length; ++i) {
            for (int j = 0; j < rebuiltVertices[i].length; ++j) {
                boolean inSegment = false;
                Vector2D p = rebuiltVertices[i][j];
                for (int k = 0; k < vertices.length; ++k) {
                    Vector2D[] loop = vertices[k];
                    int length = loop.length;
                    for (int l = 0; (! inSegment) && (l < length); ++l) {
                        inSegment = checkInSegment(p, loop[l], loop[(l + 1) % length], 1.0e-10);
                    }
                }
                Assert.assertTrue(inSegment);
            }
        }
        // each original vertex should have a corresponding rebuilt vertex
        for (int k = 0; k < vertices.length; ++k) {
            for (int l = 0; l < vertices[k].length; ++l) {
                double min = Double.POSITIVE_INFINITY;
                for (int i = 0; i < rebuiltVertices.length; ++i) {
                    for (int j = 0; j < rebuiltVertices[i].length; ++j) {
                        min = FastMath.min(vertices[k][l].distance(rebuiltVertices[i][j]),
                                       min);
                    }
                }
                Assert.assertEquals(0.0, min, 1.0e-10);
            }}}