s2/metric_test.go

// Copyright 2015 Google Inc. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package s2

import (
	"math"
	"testing"
)

func TestMetric(t *testing.T) {
	if got := MinWidthMetric.MaxLevel(0.001256); got != 9 {
		t.Errorf("MinWidthMetric.MaxLevel(0.001256) = %d, want 9", got)
	}

	// Check that the maximum aspect ratio of an individual cell is consistent
	// with the global minimums and maximums.
	if MaxEdgeAspect < 1 {
		t.Errorf("MaxEdgeAspect = %v, want >= 1", MaxEdgeAspect)
	}
	if got := MaxEdgeMetric.Deriv / MinEdgeMetric.Deriv; MaxEdgeAspect > got {
		t.Errorf("Edge Aspect: %v/%v = %v, want <= %v", MaxEdgeMetric.Deriv, MinEdgeMetric.Deriv, got, MaxDiagAspect)
	}
	if MaxDiagAspect < 1 {
		t.Errorf("MaxDiagAspect = %v, want >= 1", MaxDiagAspect)
	}
	if got := MaxDiagMetric.Deriv / MinDiagMetric.Deriv; MaxDiagAspect > got {
		t.Errorf("Diag Aspect: %v/%v = %v, want <= %v", MaxDiagMetric.Deriv, MinDiagMetric.Deriv, got, MaxDiagAspect)
	}

	// Check that area is consistent with edge and width.
	if got := MinWidthMetric.Deriv*MinEdgeMetric.Deriv - 1e-15; MinAreaMetric.Deriv < got {
		t.Errorf("Min Area: %v*%v = %v, want >= %v", MinWidthMetric.Deriv, MinEdgeMetric.Deriv, got, MinAreaMetric.Deriv)
	}
	if got := MaxWidthMetric.Deriv*MaxEdgeMetric.Deriv + 1e-15; MaxAreaMetric.Deriv > got {
		t.Errorf("Max Area: %v*%v = %v, want <= %v", MaxWidthMetric.Deriv, MaxEdgeMetric.Deriv, got, MaxAreaMetric.Deriv)
	}

	for level := -2; level <= MaxLevel+3; level++ {
		width := MinWidthMetric.Deriv * math.Pow(2, float64(-level))
		if level >= MaxLevel+3 {
			width = 0
		}

		// Check boundary cases (exactly equal to a threshold value).
		expected := int(math.Max(0, math.Min(MaxLevel, float64(level))))

		if MinWidthMetric.MinLevel(width) != expected {
			t.Errorf("MinWidthMetric.MinLevel(%v) = %v, want %v", width, MinWidthMetric.MinLevel(width), expected)
		}
		if MinWidthMetric.MaxLevel(width) != expected {
			t.Errorf("MinWidthMetric.MaxLevel(%v) = %v, want %v", width, MinWidthMetric.MaxLevel(width), expected)
		}
		if MinWidthMetric.ClosestLevel(width) != expected {
			t.Errorf("MinWidthMetric.ClosestLevel(%v) = %v, want %v", width, MinWidthMetric.ClosestLevel(width), expected)
		}

		// Also check non-boundary cases.
		if got := MinWidthMetric.MinLevel(1.2 * width); got != expected {
			t.Errorf("non-boundary MinWidthMetric.MinLevel(%v) = %v, want %v", 1.2*width, got, expected)
		}
		if got := MinWidthMetric.MaxLevel(0.8 * width); got != expected {
			t.Errorf("non-boundary MinWidthMetric.MaxLevel(%v) = %v, want %v", 0.8*width, got, expected)
		}
		if got := MinWidthMetric.ClosestLevel(1.2 * width); got != expected {
			t.Errorf("non-boundary larger MinWidthMetric.ClosestLevel(%v) = %v, want %v", 1.2*width, got, expected)
		}
		if got := MinWidthMetric.ClosestLevel(0.8 * width); got != expected {
			t.Errorf("non-boundary smaller MinWidthMetric.ClosestLevel(%v) = %v, want %v", 0.8*width, got, expected)
		}
	}
}

func TestMetricSizeRelations(t *testing.T) {
	// check that min <= avg <= max for each metric.
	tests := []struct {
		min Metric
		avg Metric
		max Metric
	}{
		{MinAngleSpanMetric, AvgAngleSpanMetric, MaxAngleSpanMetric},
		{MinWidthMetric, AvgWidthMetric, MaxWidthMetric},
		{MinEdgeMetric, AvgEdgeMetric, MaxEdgeMetric},
		{MinDiagMetric, AvgDiagMetric, MaxDiagMetric},
		{MinAreaMetric, AvgAreaMetric, MaxAreaMetric},
	}

	for _, test := range tests {
		if test.min.Deriv > test.avg.Deriv {
			t.Errorf("Min %v > Avg %v", test.min.Deriv, test.avg.Deriv)
		}
		if test.avg.Deriv > test.max.Deriv {
			t.Errorf("Avg %v > Max %v", test.avg.Deriv, test.max.Deriv)
		}
	}
}