| /* |
| * Copyright 2023 Google LLC |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #include "src/base/SkQuads.h" |
| |
| #include "include/core/SkSpan.h" |
| #include "include/core/SkTypes.h" |
| #include "include/private/base/SkFloatingPoint.h" |
| #include "src/pathops/SkPathOpsQuad.h" |
| #include "tests/Test.h" |
| |
| #include <algorithm> |
| #include <cfloat> |
| #include <cmath> |
| #include <cstddef> |
| #include <cstdint> |
| #include <iterator> |
| #include <limits> |
| #include <string> |
| |
| static void testQuadRootsReal(skiatest::Reporter* reporter, const std::string& name, |
| double A, double B, double C, |
| SkSpan<const double> expectedRoots) { |
| skiatest::ReporterContext subtest(reporter, name); |
| // Validate test case |
| REPORTER_ASSERT(reporter, expectedRoots.size() <= 2, |
| "Invalid test case, up to 2 roots allowed"); |
| |
| for (size_t i = 0; i < expectedRoots.size(); i++) { |
| double x = expectedRoots[i]; |
| // A*x^2 + B*x + C should equal 0 |
| double y = A * x * x + B * x + C; |
| REPORTER_ASSERT(reporter, sk_double_nearly_zero(y), |
| "Invalid test case root %zu. %.16f != 0", i, y); |
| |
| if (i > 0) { |
| REPORTER_ASSERT(reporter, expectedRoots[i-1] <= expectedRoots[i], |
| "Invalid test case root %zu. Roots should be sorted in ascending order", i); |
| } |
| } |
| |
| { |
| skiatest::ReporterContext subsubtest(reporter, "Pathops Implementation"); |
| double roots[2] = {0, 0}; |
| int rootCount = SkDQuad::RootsReal(A, B, C, roots); |
| REPORTER_ASSERT(reporter, expectedRoots.size() == size_t(rootCount), |
| "Wrong number of roots returned %zu != %d", expectedRoots.size(), |
| rootCount); |
| |
| // We don't care which order the roots are returned from the algorithm. |
| // For determinism, we will sort them (and ensure the provided solutions are also sorted). |
| std::sort(std::begin(roots), std::begin(roots) + rootCount); |
| for (int i = 0; i < rootCount; i++) { |
| if (sk_double_nearly_zero(expectedRoots[i])) { |
| REPORTER_ASSERT(reporter, sk_double_nearly_zero(roots[i]), |
| "0 != %.16f at index %d", roots[i], i); |
| } else { |
| REPORTER_ASSERT(reporter, |
| sk_doubles_nearly_equal_ulps(expectedRoots[i], roots[i], 64), |
| "%.16f != %.16f at index %d", expectedRoots[i], roots[i], i); |
| } |
| } |
| } |
| { |
| skiatest::ReporterContext subsubtest(reporter, "SkQuads Implementation"); |
| double roots[2] = {0, 0}; |
| int rootCount = SkQuads::RootsReal(A, B, C, roots); |
| REPORTER_ASSERT(reporter, expectedRoots.size() == size_t(rootCount), |
| "Wrong number of roots returned %zu != %d", expectedRoots.size(), |
| rootCount); |
| |
| // We don't care which order the roots are returned from the algorithm. |
| // For determinism, we will sort them (and ensure the provided solutions are also sorted). |
| std::sort(std::begin(roots), std::begin(roots) + rootCount); |
| for (int i = 0; i < rootCount; i++) { |
| if (sk_double_nearly_zero(expectedRoots[i])) { |
| REPORTER_ASSERT(reporter, sk_double_nearly_zero(roots[i]), |
| "0 != %.16f at index %d", roots[i], i); |
| } else { |
| REPORTER_ASSERT(reporter, |
| sk_doubles_nearly_equal_ulps(expectedRoots[i], roots[i], 64), |
| "%.16f != %.16f at index %d", expectedRoots[i], roots[i], i); |
| } |
| } |
| } |
| } |
| |
| DEF_TEST(QuadRootsReal_ActualQuadratics, reporter) { |
| // All answers are given with 16 significant digits (max for a double) or as an integer |
| // when the answer is exact. |
| testQuadRootsReal(reporter, "two roots 3x^2 - 20x - 40", |
| 3, -20, -40, |
| {-1.610798991397109, |
| //-1.610798991397108632474265 from Wolfram Alpha |
| 8.277465658063775, |
| // 8.277465658063775299140932 from Wolfram Alpha |
| }); |
| |
| // (2x - 4)(x + 17) |
| testQuadRootsReal(reporter, "two roots 2x^2 + 30x - 68", |
| 2, 30, -68, |
| {-17, 2}); |
| |
| testQuadRootsReal(reporter, "two roots x^2 - 5", |
| 1, 0, -5, |
| {-2.236067977499790, |
| //-2.236067977499789696409174 from Wolfram Alpha |
| 2.236067977499790, |
| // 2.236067977499789696409174 from Wolfram Alpha |
| }); |
| |
| testQuadRootsReal(reporter, "one root x^2 - 2x + 1", |
| 1, -2, 1, |
| {1}); |
| |
| testQuadRootsReal(reporter, "no roots 5x^2 + 6x + 7", |
| 5, 6, 7, |
| {}); |
| |
| testQuadRootsReal(reporter, "no roots 4x^2 + 1", |
| 4, 0, 1, |
| {}); |
| |
| testQuadRootsReal(reporter, "one root is zero, another is big", |
| 14, -13, 0, |
| {0, |
| 0.9285714285714286 |
| //0.9285714285714285714285714 from Wolfram Alpha |
| }); |
| |
| // Values from a failing test case observed during testing. |
| testQuadRootsReal(reporter, "one root is zero, another is small", |
| 0.2929016490705016, 0.0000030451558069, 0, |
| {-0.00001039651301576329, 0}); |
| |
| testQuadRootsReal(reporter, "b and c are zero, a is positive 4x^2", |
| 4, 0, 0, |
| {0}); |
| |
| testQuadRootsReal(reporter, "b and c are zero, a is negative -4x^2", |
| -4, 0, 0, |
| {0}); |
| |
| testQuadRootsReal(reporter, "a and b are huge, c is zero", |
| 4.3719914983870202e+291, 1.0269509510194551e+152, 0, |
| // One solution is 0, the other is so close to zero it returns |
| // true for sk_double_nearly_zero, so it is collapsed into one. |
| {0}); |
| |
| testQuadRootsReal(reporter, "Very small A B, very large C", |
| 0x1p-1055, 0x1.3000006p-1044, -0x1.c000008p+1009, |
| // The roots are not in the range of doubles. |
| {}); |
| } |
| |
| DEF_TEST(QuadRootsReal_Linear, reporter) { |
| testQuadRootsReal(reporter, "positive slope 5x + 6", |
| 0, 5, 6, |
| {-1.2}); |
| |
| testQuadRootsReal(reporter, "negative slope -3x - 9", |
| 0, -3, -9, |
| {-3.}); |
| } |
| |
| DEF_TEST(QuadRootsReal_Constant, reporter) { |
| testQuadRootsReal(reporter, "No intersections y = -10", |
| 0, 0, -10, |
| {}); |
| |
| testQuadRootsReal(reporter, "Infinite solutions y = 0", |
| 0, 0, 0, |
| {0.}); |
| } |
| |
| DEF_TEST(QuadRootsReal_NonFiniteNumbers, reporter) { |
| // The Pathops implementation does not check for infinities nor nans in all cases. |
| double roots[2]; |
| REPORTER_ASSERT(reporter, |
| SkQuads::RootsReal(DBL_MAX, 0, DBL_MAX, roots) == 0, |
| "Discriminant is negative infinity" |
| ); |
| REPORTER_ASSERT(reporter, |
| SkQuads::RootsReal(DBL_MAX, DBL_MAX, DBL_MAX, roots) == 0, |
| "Double Overflow" |
| ); |
| |
| REPORTER_ASSERT(reporter, |
| SkQuads::RootsReal(1, NAN, -3, roots) == 0, |
| "Nan quadratic" |
| ); |
| REPORTER_ASSERT(reporter, |
| SkQuads::RootsReal(0, NAN, 3, roots) == 0, |
| "Nan linear" |
| ); |
| REPORTER_ASSERT(reporter, |
| SkQuads::RootsReal(0, 0, NAN, roots) == 0, |
| "Nan constant" |
| ); |
| } |
| |
| // Test the discriminant using |
| // Use quadratics of the form F_n * x^2 - 2 * F_(n-1) * x + F_(n-2). |
| // This has a discriminant of F_(n-1)^2 - F_n * F_(n-2) = 1 if n is even else -1. |
| DEF_TEST(QuadDiscriminant_Fibonacci, reporter) { |
| // n, n-1, n-2 |
| int64_t F[] = {1, 1, 0}; |
| // F_79 just fits in the 53 significant bits of a double. |
| for (int i = 2; i < 79; ++i) { |
| F[0] = F[1] + F[2]; |
| |
| const int expectedDiscriminant = i % 2 == 0 ? 1 : -1; |
| REPORTER_ASSERT(reporter, SkQuads::Discriminant(F[0], F[1], F[2]) == expectedDiscriminant); |
| |
| F[2] = F[1]; |
| F[1] = F[0]; |
| } |
| } |
| |
| DEF_TEST(QuadRoots_Basic, reporter) { |
| { |
| // (x - 1) (x - 1) normal quadratic form A = 1, B = 2, C =1. |
| auto [discriminant, r0, r1] = SkQuads::Roots(1, -0.5 * -2, 1); |
| REPORTER_ASSERT(reporter, discriminant == 0); |
| REPORTER_ASSERT(reporter, r0 == 1 && r1 == 1); |
| } |
| |
| { |
| // (x + 2) (x + 2) normal quadratic form A = 1, B = 4, C = 4. |
| auto [discriminant, r0, r1] = SkQuads::Roots(1, -0.5 * 4, 4); |
| REPORTER_ASSERT(reporter, discriminant == 0); |
| REPORTER_ASSERT(reporter, r0 == -2 && r1 == -2); |
| } |
| } |
| |
| // Test the roots using |
| // Use quadratics of the form F_n * x^2 - 2 * F_(n-1) * x + F_(n-2). |
| // The roots are (F_(n–1) ± 1)/F_n if n is even otherwise there are no roots. |
| DEF_TEST(QuadRoots_Fibonacci, reporter) { |
| // n, n-1, n-2 |
| int64_t F[] = {1, 1, 0}; |
| // F_79 just fits in the 53 significant bits of a double. |
| for (int i = 2; i < 79; ++i) { |
| F[0] = F[1] + F[2]; |
| |
| const int expectedDiscriminant = i % 2 == 0 ? 1 : -1; |
| auto [discriminant, r0, r1] = SkQuads::Roots(F[0], F[1], F[2]); |
| REPORTER_ASSERT(reporter, discriminant == expectedDiscriminant); |
| |
| // There are only real roots when i is even. |
| if (i % 2 == 0) { |
| const double expectedLittle = ((double)F[1] - 1) / F[0]; |
| const double expectedBig = ((double)F[1] + 1) / F[0]; |
| if (r0 <= r1) { |
| REPORTER_ASSERT(reporter, r0 == expectedLittle); |
| REPORTER_ASSERT(reporter, r1 == expectedBig); |
| } else { |
| REPORTER_ASSERT(reporter, r1 == expectedLittle); |
| REPORTER_ASSERT(reporter, r0 == expectedBig); |
| } |
| } else { |
| REPORTER_ASSERT(reporter, std::isnan(r0)); |
| REPORTER_ASSERT(reporter, std::isnan(r1)); |
| } |
| |
| F[2] = F[1]; |
| F[1] = F[0]; |
| } |
| } |
| |
| // These are test cases used in the paper "The Ins and Outs of Solving Quadratic Equations with |
| // Floating-Point Arithmetic" located at |
| // https://github.com/goualard-f/QuadraticEquation.jl/blob/main/test/tests.jl |
| |
| struct TestCase { |
| const double A; |
| const double B; |
| const double C; |
| const double answerLo; |
| const double answerHi; |
| }; |
| |
| DEF_TEST(QuadRoots_Hard, reporter) { |
| const double nan = std::numeric_limits<double>::quiet_NaN(); |
| const double infinity = std::numeric_limits<double>::infinity(); |
| |
| auto specialEqual = [] (double actual, double test) { |
| if (std::isnan(actual)) { |
| return std::isnan(test); |
| } |
| |
| if (std::isinf(actual)) { |
| return std::isinf(test); |
| } |
| |
| // Comparison function from the paper "The Ins and Outs ...." |
| const double errorFactor = std::sqrt(std::numeric_limits<double>::epsilon()); |
| return std::abs(test - actual) <= errorFactor * std::max(std::abs(test), std::abs(actual)); |
| }; |
| |
| auto p2 = [](double a) { |
| return std::exp2(a); |
| }; |
| |
| TestCase cases[] = { |
| // no real solutions |
| {2, 0, 3, nan, nan}, |
| {1, 1, 1, nan, nan}, |
| {2.0 * p2(600), 0, 2.0 * p2(600), nan, nan}, |
| {-2.0 * p2(600), 0, -2.0 * p2(600), nan, nan}, |
| |
| // degenerate cases |
| {0, 0, 0, infinity, infinity}, |
| {0, 1, 0, 0, 0}, |
| {0, 1, 2, -2, -2}, |
| {0, 3, 4, -4.0/3.0, -4.0/3.0}, |
| {0, p2(600), -p2(600), 1, 1}, |
| {0, p2(600), p2(600), -1, -1}, |
| {0, p2(-600), p2(600), -infinity, -infinity}, |
| {0, p2(600), p2(-600), 0, 0}, |
| {0, 2, -1.0e-323, 5.0e-324, 5.0e-324}, |
| {3, 0, 0, 0, 0}, |
| {p2(600), 0, 0, 0, 0}, |
| {2, 0, -3, -sqrt(3.0/2.0), sqrt(3.0/2.0)}, |
| // {p2(600), 0, -p2(600), -1, 1}, determinant is infinity |
| {3, 2, 0, -2.0/3.0, 0}, |
| // {p2(600), p2(700), 0, -p2(100), 0}, |
| {p2(-600), p2(700), 0, -infinity, 0}, |
| {p2(600), p2(-700), 0, 0, 0}, |
| |
| // two solutions tests |
| {1, -1, -1, -0.6180339887498948, 1.618033988749895}, |
| {1, 1 + p2(-52), 0.25 + p2(-53), (-1 - p2(-51)) / 2.0, -0.5}, |
| {1, p2(-511) + p2(-563), std::exp2(-1024), -7.458340888372987e-155,-7.458340574027429e-155}, |
| {1, p2(27), 0.75, -134217728.0, -5.587935447692871e-09}, |
| {1, -1e9, 1, 1e-09, 1000000000.0}, |
| // {1.3407807929942596e154, -1.3407807929942596e154, -1.3407807929942596e154, -0.6180339887498948, 1.618033988749895}, |
| {p2(600), 0.5, -p2(-600), -3.086568504549085e-181, 1.8816085719976428e-181}, |
| // {p2(600), 0.5, -p2(600), -1.0, 1.0}, |
| // {8.0, p2(800),-p2(500), -8.335018041099818e+239, 4.909093465297727e-91}, |
| {1, p2(26), -0.125, -67108864.0, 1.862645149230957e-09}, |
| // {p2(-1073), -p2(-1073), -p2(-1073), -0.6180339887498948,1.618033988749895}, |
| {p2(600), -p2(-600), -p2(-600), -2.409919865102884e-181, 2.409919865102884e-181}, |
| |
| // Tests in Nivergelt paper |
| {-158114166017, 316227766017, -158113600000, 0.99999642020057874, 1}, |
| {-312499999999.0, 707106781186.0, -400000000000.0, 1.131369396027, 1.131372303775}, |
| {-67, 134, -65, 0.82722631488372798, 1.17277368511627202}, |
| {0.247260273973, 0.994520547945, -0.138627953316, -4.157030027041105, 0.1348693622211607}, |
| {1, -2300000, 2.0e11, 90518.994979145, 2209481.005020854}, |
| {1.5*p2(-1026), 0, -p2(1022), -1.4678102981723264e308, 1.4678102981723264e308}, |
| |
| // one solution tests |
| {1.5*p2(-1026), 0, -p2(1022), -1.4678102981723264e308, 1.4678102981723264e308}, |
| }; |
| |
| for (auto testCase : cases) { |
| double A = testCase.A, |
| B = testCase.B, |
| C = testCase.C, |
| answerLo = testCase.answerLo, |
| answerHi = testCase.answerHi; |
| if (SkIsFinite(answerLo, answerHi)) { |
| SkASSERT(answerLo <= answerHi); |
| } |
| auto [discriminate, r0, r1] = SkQuads::Roots(A, -0.5*B, C); |
| double rLo = std::min(r0, r1), |
| rHi = std::max(r0, r1); |
| REPORTER_ASSERT(reporter, specialEqual(rLo, answerLo)); |
| REPORTER_ASSERT(reporter, specialEqual(rHi, answerHi)); |
| } |
| } |
| |
