Revise SVD code to remove arctangents.

Also added bench for timing matrix decomposition.

R=reed@google.com

Author: jvanverth@google.com

Review URL: https://chromiumcodereview.appspot.com/23596006

git-svn-id: http://skia.googlecode.com/svn/trunk@11066 2bbb7eff-a529-9590-31e7-b0007b416f81

2 files changed, 83 insertions, 134 deletions

diff --git a/tests/Matrix44Test.cpp b/tests/Matrix44Test.cpp
index 67af60df90..6c29a55966 100644
--- a/tests/Matrix44Test.cpp
+++ b/tests/Matrix44Test.cpp
@@ -513,10 +513,10 @@ static void TestMatrix44(skiatest::Reporter* reporter) {
 
     // test mixed-valued matrix inverse
     mat.reset();
-    mat.setScale(1.0e-10, 3.0, 1.0e+10);
+    mat.setScale(1.0e-11, 3.0, 1.0e+11);
     rot.setRotateDegreesAbout(0, 0, -1, 90);
     mat.postConcat(rot);
-    mat.postTranslate(1.0e+10, 3.0, 1.0e-10);
+    mat.postTranslate(1.0e+11, 3.0, 1.0e-11);
     REPORTER_ASSERT(reporter, mat.invert(NULL));
     mat.invert(&inverse);
     iden1.setConcat(mat, inverse);
diff --git a/tests/MatrixTest.cpp b/tests/MatrixTest.cpp
index 8785730322..c225565cc4 100644
--- a/tests/MatrixTest.cpp
+++ b/tests/MatrixTest.cpp
@@ -350,11 +350,13 @@ static void test_matrix_is_similarity(skiatest::Reporter* reporter) {
 static bool scalar_nearly_equal_relative(SkScalar a, SkScalar b,
                                          SkScalar tolerance = SK_ScalarNearlyZero) {
     // from Bruce Dawson
+    // absolute check
     SkScalar diff = SkScalarAbs(a - b);
     if (diff < tolerance) {
         return true;
     }
 
+    // relative check
     a = SkScalarAbs(a);
     b = SkScalarAbs(b);
     SkScalar largest = (b > a) ? b : a;
@@ -366,9 +368,32 @@ static bool scalar_nearly_equal_relative(SkScalar a, SkScalar b,
     return false;
 }
 
+static bool check_matrix_recomposition(const SkMatrix& mat,
+                                       const SkPoint& rotation1,
+                                       const SkPoint& scale,
+                                       const SkPoint& rotation2) {
+    SkScalar c1 = rotation1.fX;
+    SkScalar s1 = rotation1.fY;
+    SkScalar scaleX = scale.fX;
+    SkScalar scaleY = scale.fY;
+    SkScalar c2 = rotation2.fX;
+    SkScalar s2 = rotation2.fY;
+    
+    // We do a relative check here because large scale factors cause problems with an absolute check
+    bool result = scalar_nearly_equal_relative(mat[SkMatrix::kMScaleX],
+                                               scaleX*c1*c2 - scaleY*s1*s2) &&
+                  scalar_nearly_equal_relative(mat[SkMatrix::kMSkewX],
+                                               -scaleX*s1*c2 - scaleY*c1*s2) &&
+                  scalar_nearly_equal_relative(mat[SkMatrix::kMSkewY],
+                                               scaleX*c1*s2 + scaleY*s1*c2) &&
+                  scalar_nearly_equal_relative(mat[SkMatrix::kMScaleY],
+                                               -scaleX*s1*s2 + scaleY*c1*c2);
+    return result;
+}
+
 static void test_matrix_decomposition(skiatest::Reporter* reporter) {
     SkMatrix mat;
-    SkScalar rotation0, scaleX, scaleY, rotation1;
+    SkPoint rotation1, scale, rotation2;
 
     const float kRotation0 = 15.5f;
     const float kRotation1 = -50.f;
@@ -377,150 +402,108 @@ static void test_matrix_decomposition(skiatest::Reporter* reporter) {
 
     // identity
     mat.reset();
-    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation0, &scaleX, &scaleY, &rotation1));
-    REPORTER_ASSERT(reporter, SkScalarNearlyZero(rotation0));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(scaleX, SK_Scalar1));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(scaleY, SK_Scalar1));
-    REPORTER_ASSERT(reporter, SkScalarNearlyZero(rotation1));
+    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation1, &scale, &rotation2));
+    REPORTER_ASSERT(reporter, check_matrix_recomposition(mat, rotation1, scale, rotation2));
     // make sure it doesn't crash if we pass in NULLs
-    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, NULL, NULL, NULL, NULL));
+    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, NULL, NULL, NULL));
 
     // rotation only
     mat.setRotate(kRotation0);
-    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation0, &scaleX, &scaleY, &rotation1));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(rotation0, SkDegreesToRadians(kRotation0)));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(scaleX, SK_Scalar1));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(scaleY, SK_Scalar1));
-    REPORTER_ASSERT(reporter, SkScalarNearlyZero(rotation1));
+    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation1, &scale, &rotation2));
+    REPORTER_ASSERT(reporter, check_matrix_recomposition(mat, rotation1, scale, rotation2));
 
     // uniform scale only
     mat.setScale(kScale0, kScale0);
-    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation0, &scaleX, &scaleY, &rotation1));
-    REPORTER_ASSERT(reporter, SkScalarNearlyZero(rotation0));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(scaleX, kScale0));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(scaleY, kScale0));
-    REPORTER_ASSERT(reporter, SkScalarNearlyZero(rotation1));
+    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation1, &scale, &rotation2));
+    REPORTER_ASSERT(reporter, check_matrix_recomposition(mat, rotation1, scale, rotation2));
 
     // anisotropic scale only
     mat.setScale(kScale1, kScale0);
-    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation0, &scaleX, &scaleY, &rotation1));
-    REPORTER_ASSERT(reporter, SkScalarNearlyZero(rotation0));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(scaleX, kScale1));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(scaleY, kScale0));
-    REPORTER_ASSERT(reporter, SkScalarNearlyZero(rotation1));
+    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation1, &scale, &rotation2));
+    REPORTER_ASSERT(reporter, check_matrix_recomposition(mat, rotation1, scale, rotation2));
 
     // rotation then uniform scale
     mat.setRotate(kRotation1);
     mat.postScale(kScale0, kScale0);
-    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation0, &scaleX, &scaleY, &rotation1));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(rotation0, SkDegreesToRadians(kRotation1)));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(scaleX, kScale0));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(scaleY, kScale0));
-    REPORTER_ASSERT(reporter, SkScalarNearlyZero(rotation1));
+    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation1, &scale, &rotation2));
+    REPORTER_ASSERT(reporter, check_matrix_recomposition(mat, rotation1, scale, rotation2));
 
     // uniform scale then rotation
     mat.setScale(kScale0, kScale0);
     mat.postRotate(kRotation1);
-    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation0, &scaleX, &scaleY, &rotation1));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(rotation0, SkDegreesToRadians(kRotation1)));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(scaleX, kScale0));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(scaleY, kScale0));
-    REPORTER_ASSERT(reporter, SkScalarNearlyZero(rotation1));
+    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation1, &scale, &rotation2));
+    REPORTER_ASSERT(reporter, check_matrix_recomposition(mat, rotation1, scale, rotation2));
 
     // rotation then uniform scale+reflection
     mat.setRotate(kRotation0);
     mat.postScale(kScale1, -kScale1);
-    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation0, &scaleX, &scaleY, &rotation1));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(rotation0, SkDegreesToRadians(kRotation0)));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(scaleX, kScale1));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(scaleY, -kScale1));
-    REPORTER_ASSERT(reporter, SkScalarNearlyZero(rotation1));
+    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation1, &scale, &rotation2));
+    REPORTER_ASSERT(reporter, check_matrix_recomposition(mat, rotation1, scale, rotation2));
 
     // uniform scale+reflection, then rotate
     mat.setScale(kScale0, -kScale0);
     mat.postRotate(kRotation1);
-    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation0, &scaleX, &scaleY, &rotation1));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(rotation0, SkDegreesToRadians(-kRotation1)));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(scaleX, kScale0));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(scaleY, -kScale0));
-    REPORTER_ASSERT(reporter, SkScalarNearlyZero(rotation1));
+    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation1, &scale, &rotation2));
+    REPORTER_ASSERT(reporter, check_matrix_recomposition(mat, rotation1, scale, rotation2));
 
     // rotation then anisotropic scale
     mat.setRotate(kRotation1);
     mat.postScale(kScale1, kScale0);
-    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation0, &scaleX, &scaleY, &rotation1));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(rotation0, SkDegreesToRadians(kRotation1)));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(scaleX, kScale1));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(scaleY, kScale0));
-    REPORTER_ASSERT(reporter, SkScalarNearlyZero(rotation1));
+    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation1, &scale, &rotation2));
+    REPORTER_ASSERT(reporter, check_matrix_recomposition(mat, rotation1, scale, rotation2));
 
+    // rotation then anisotropic scale
+    mat.setRotate(90);
+    mat.postScale(kScale1, kScale0);
+    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation1, &scale, &rotation2));
+    REPORTER_ASSERT(reporter, check_matrix_recomposition(mat, rotation1, scale, rotation2));
+    
     // anisotropic scale then rotation
     mat.setScale(kScale1, kScale0);
     mat.postRotate(kRotation0);
-    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation0, &scaleX, &scaleY, &rotation1));
-    REPORTER_ASSERT(reporter, SkScalarNearlyZero(rotation0));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(scaleX, kScale1));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(scaleY, kScale0));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(rotation1, SkDegreesToRadians(kRotation0)));
+    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation1, &scale, &rotation2));
+    REPORTER_ASSERT(reporter, check_matrix_recomposition(mat, rotation1, scale, rotation2));
+    
+    // anisotropic scale then rotation
+    mat.setScale(kScale1, kScale0);
+    mat.postRotate(90);
+    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation1, &scale, &rotation2));
+    REPORTER_ASSERT(reporter, check_matrix_recomposition(mat, rotation1, scale, rotation2));
 
     // rotation, uniform scale, then different rotation
     mat.setRotate(kRotation1);
     mat.postScale(kScale0, kScale0);
     mat.postRotate(kRotation0);
-    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation0, &scaleX, &scaleY, &rotation1));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(rotation0,
-                                                  SkDegreesToRadians(kRotation0 + kRotation1)));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(scaleX, kScale0));
-    REPORTER_ASSERT(reporter, SkScalarNearlyEqual(scaleY, kScale0));
-    REPORTER_ASSERT(reporter, SkScalarNearlyZero(rotation1));
+    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation1, &scale, &rotation2));
+    REPORTER_ASSERT(reporter, check_matrix_recomposition(mat, rotation1, scale, rotation2));
 
     // rotation, anisotropic scale, then different rotation
     mat.setRotate(kRotation0);
     mat.postScale(kScale1, kScale0);
     mat.postRotate(kRotation1);
-    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation0, &scaleX, &scaleY, &rotation1));
-    // Because of the shear/skew we won't get the same results, so we need to multiply it out.
-    // Generating the matrices requires doing a radian-to-degree calculation, then degree-to-radian
-    // calculation (in setRotate()), which adds error, so this just computes the matrix elements
-    // directly.
-    SkScalar c0;
-    SkScalar s0 = SkScalarSinCos(rotation0, &c0);
-    SkScalar c1;
-    SkScalar s1 = SkScalarSinCos(rotation1, &c1);
-    // We do a relative check here because large scale factors cause problems with an absolute check
-    REPORTER_ASSERT(reporter, scalar_nearly_equal_relative(mat[SkMatrix::kMScaleX],
-                                                           scaleX*c0*c1 - scaleY*s0*s1));
-    REPORTER_ASSERT(reporter, scalar_nearly_equal_relative(mat[SkMatrix::kMSkewX],
-                                                           -scaleX*s0*c1 - scaleY*c0*s1));
-    REPORTER_ASSERT(reporter, scalar_nearly_equal_relative(mat[SkMatrix::kMSkewY],
-                                                           scaleX*c0*s1 + scaleY*s0*c1));
-    REPORTER_ASSERT(reporter, scalar_nearly_equal_relative(mat[SkMatrix::kMScaleY],
-                                                           -scaleX*s0*s1 + scaleY*c0*c1));
+    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation1, &scale, &rotation2));
+    REPORTER_ASSERT(reporter, check_matrix_recomposition(mat, rotation1, scale, rotation2));
+    
+    // rotation, anisotropic scale + reflection, then different rotation
+    mat.setRotate(kRotation0);
+    mat.postScale(-kScale1, kScale0);
+    mat.postRotate(kRotation1);
+    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation1, &scale, &rotation2));
+    REPORTER_ASSERT(reporter, check_matrix_recomposition(mat, rotation1, scale, rotation2));
 
     // try some random matrices
     SkMWCRandom rand;
     for (int m = 0; m < 1000; ++m) {
-        SkScalar rot0 = rand.nextRangeF(-SK_ScalarPI, SK_ScalarPI);
+        SkScalar rot0 = rand.nextRangeF(-180, 180);
         SkScalar sx = rand.nextRangeF(-3000.f, 3000.f);
         SkScalar sy = rand.nextRangeF(-3000.f, 3000.f);
-        SkScalar rot1 = rand.nextRangeF(-SK_ScalarPI, SK_ScalarPI);
+        SkScalar rot1 = rand.nextRangeF(-180, 180);
         mat.setRotate(rot0);
         mat.postScale(sx, sy);
         mat.postRotate(rot1);
 
-        if (SkDecomposeUpper2x2(mat, &rotation0, &scaleX, &scaleY, &rotation1)) {
-            SkScalar c0;
-            SkScalar s0 = SkScalarSinCos(rotation0, &c0);
-            SkScalar c1;
-            SkScalar s1 = SkScalarSinCos(rotation1, &c1);
-            REPORTER_ASSERT(reporter, scalar_nearly_equal_relative(mat[SkMatrix::kMScaleX],
-                                                                   scaleX*c0*c1 - scaleY*s0*s1));
-            REPORTER_ASSERT(reporter, scalar_nearly_equal_relative(mat[SkMatrix::kMSkewX],
-                                                                   -scaleX*s0*c1 - scaleY*c0*s1));
-            REPORTER_ASSERT(reporter, scalar_nearly_equal_relative(mat[SkMatrix::kMSkewY],
-                                                                   scaleX*c0*s1 + scaleY*s0*c1));
-            REPORTER_ASSERT(reporter, scalar_nearly_equal_relative(mat[SkMatrix::kMScaleY],
-                                                                   -scaleX*s0*s1 + scaleY*c0*c1));
+        if (SkDecomposeUpper2x2(mat, &rotation1, &scale, &rotation2)) {
+            REPORTER_ASSERT(reporter, check_matrix_recomposition(mat, rotation1, scale, rotation2));
         } else {
             // if the matrix is degenerate, the basis vectors should be near-parallel or near-zero
             SkScalar perpdot = mat[SkMatrix::kMScaleX]*mat[SkMatrix::kMScaleY] -
@@ -531,65 +514,31 @@ static void test_matrix_decomposition(skiatest::Reporter* reporter) {
 
     // translation shouldn't affect this
     mat.postTranslate(-1000.f, 1000.f);
-    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation0, &scaleX, &scaleY, &rotation1));
-    s0 = SkScalarSinCos(rotation0, &c0);
-    s1 = SkScalarSinCos(rotation1, &c1);
-    REPORTER_ASSERT(reporter, scalar_nearly_equal_relative(mat[SkMatrix::kMScaleX],
-                                                           scaleX*c0*c1 - scaleY*s0*s1));
-    REPORTER_ASSERT(reporter, scalar_nearly_equal_relative(mat[SkMatrix::kMSkewX],
-                                                           -scaleX*s0*c1 - scaleY*c0*s1));
-    REPORTER_ASSERT(reporter, scalar_nearly_equal_relative(mat[SkMatrix::kMSkewY],
-                                                           scaleX*c0*s1 + scaleY*s0*c1));
-    REPORTER_ASSERT(reporter, scalar_nearly_equal_relative(mat[SkMatrix::kMScaleY],
-                                                           -scaleX*s0*s1 + scaleY*c0*c1));
+    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation1, &scale, &rotation2));
+    REPORTER_ASSERT(reporter, check_matrix_recomposition(mat, rotation1, scale, rotation2));
 
     // perspective shouldn't affect this
     mat[SkMatrix::kMPersp0] = 12.f;
     mat[SkMatrix::kMPersp1] = 4.f;
     mat[SkMatrix::kMPersp2] = 1872.f;
-    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation0, &scaleX, &scaleY, &rotation1));
-    s0 = SkScalarSinCos(rotation0, &c0);
-    s1 = SkScalarSinCos(rotation1, &c1);
-    REPORTER_ASSERT(reporter, scalar_nearly_equal_relative(mat[SkMatrix::kMScaleX],
-                                                           scaleX*c0*c1 - scaleY*s0*s1));
-    REPORTER_ASSERT(reporter, scalar_nearly_equal_relative(mat[SkMatrix::kMSkewX],
-                                                           -scaleX*s0*c1 - scaleY*c0*s1));
-    REPORTER_ASSERT(reporter, scalar_nearly_equal_relative(mat[SkMatrix::kMSkewY],
-                                                           scaleX*c0*s1 + scaleY*s0*c1));
-    REPORTER_ASSERT(reporter, scalar_nearly_equal_relative(mat[SkMatrix::kMScaleY],
-                                                           -scaleX*s0*s1 + scaleY*c0*c1));
-
-    // rotation, anisotropic scale + reflection, then different rotation
-    mat.setRotate(kRotation0);
-    mat.postScale(-kScale1, kScale0);
-    mat.postRotate(kRotation1);
-    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation0, &scaleX, &scaleY, &rotation1));
-    s0 = SkScalarSinCos(rotation0, &c0);
-    s1 = SkScalarSinCos(rotation1, &c1);
-    REPORTER_ASSERT(reporter, scalar_nearly_equal_relative(mat[SkMatrix::kMScaleX],
-                                                           scaleX*c0*c1 - scaleY*s0*s1));
-    REPORTER_ASSERT(reporter, scalar_nearly_equal_relative(mat[SkMatrix::kMSkewX],
-                                                           -scaleX*s0*c1 - scaleY*c0*s1));
-    REPORTER_ASSERT(reporter, scalar_nearly_equal_relative(mat[SkMatrix::kMSkewY],
-                                                           scaleX*c0*s1 + scaleY*s0*c1));
-    REPORTER_ASSERT(reporter, scalar_nearly_equal_relative(mat[SkMatrix::kMScaleY],
-                                                           -scaleX*s0*s1 + scaleY*c0*c1));
+    REPORTER_ASSERT(reporter, SkDecomposeUpper2x2(mat, &rotation1, &scale, &rotation2));
+    REPORTER_ASSERT(reporter, check_matrix_recomposition(mat, rotation1, scale, rotation2));
 
     // degenerate matrices
     // mostly zero entries
     mat.reset();
     mat[SkMatrix::kMScaleX] = 0.f;
-    REPORTER_ASSERT(reporter, !SkDecomposeUpper2x2(mat, &rotation0, &scaleX, &scaleY, &rotation1));
+    REPORTER_ASSERT(reporter, !SkDecomposeUpper2x2(mat, &rotation1, &scale, &rotation2));
     mat.reset();
     mat[SkMatrix::kMScaleY] = 0.f;
-    REPORTER_ASSERT(reporter, !SkDecomposeUpper2x2(mat, &rotation0, &scaleX, &scaleY, &rotation1));
+    REPORTER_ASSERT(reporter, !SkDecomposeUpper2x2(mat, &rotation1, &scale, &rotation2));
     mat.reset();
     // linearly dependent entries
     mat[SkMatrix::kMScaleX] = 1.f;
     mat[SkMatrix::kMSkewX] = 2.f;
     mat[SkMatrix::kMSkewY] = 4.f;
     mat[SkMatrix::kMScaleY] = 8.f;
-    REPORTER_ASSERT(reporter, !SkDecomposeUpper2x2(mat, &rotation0, &scaleX, &scaleY, &rotation1));
+    REPORTER_ASSERT(reporter, !SkDecomposeUpper2x2(mat, &rotation1, &scale, &rotation2));
 }
 
 // For test_matrix_homogeneous, below.