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skia2/tests/PathOpsCubicLineIntersectionIdeas.cpp
caryclark a35ab3e6e0 fix fuzzers 
Many old pathops-related fuzz failures have built up while
the codebase was under a state a flux. Now that the code
is stable, address these failures.

Most of the CL plumbs the debug global state to downstream
routines so that, if the data is not trusted (ala fuzzed)
the function can safely exit without asserting.

TBR=reed@google.com
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2426173002

Review-Url: https://chromiumcodereview.appspot.com/2426173002
2016-10-20 08:32:18 -07:00

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/*
* Copyright 2014 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "PathOpsTestCommon.h"
#include "SkIntersections.h"
#include "SkPathOpsCubic.h"
#include "SkPathOpsLine.h"
#include "SkPathOpsQuad.h"
#include "SkRandom.h"
#include "SkReduceOrder.h"
#include "Test.h"
static bool gPathOpsCubicLineIntersectionIdeasVerbose = false;
static struct CubicLineFailures {
CubicPts c;
double t;
SkDPoint p;
} cubicLineFailures[] = {
{{{{-164.3726806640625, 36.826904296875}, {-189.045166015625, -953.2220458984375},
{926.505859375, -897.36175537109375}, {-139.33489990234375, 204.40771484375}}},
0.37329583, {107.54935269006289, -632.13736293162208}},
{{{{784.056884765625, -554.8350830078125}, {67.5489501953125, 509.0224609375},
{-447.713134765625, 751.375}, {415.7784423828125, 172.22265625}}},
0.660005242, {-32.973148967736151, 478.01341797403569}},
{{{{-580.6834716796875, -127.044921875}, {-872.8983154296875, -945.54302978515625},
{260.8092041015625, -909.34991455078125}, {-976.2125244140625, -18.46551513671875}}},
0.578826774, {-390.17910153915489, -687.21144412296007}},
};
int cubicLineFailuresCount = (int) SK_ARRAY_COUNT(cubicLineFailures);
double measuredSteps[] = {
9.15910731e-007, 8.6600277e-007, 7.4122059e-007, 6.92087618e-007, 8.35290245e-007,
3.29763199e-007, 5.07547773e-007, 4.41294224e-007, 0, 0,
3.76879167e-006, 1.06126249e-006, 2.36873967e-006, 1.62421134e-005, 3.09103599e-005,
4.38917976e-005, 0.000112348938, 0.000243149242, 0.000433174114, 0.00170880232,
0.00272619724, 0.00518844604, 0.000352621078, 0.00175960064, 0.027875185,
0.0351329803, 0.103964925,
};
/* last output : errors=3121
9.1796875e-007 8.59375e-007 7.5e-007 6.875e-007 8.4375e-007
3.125e-007 5e-007 4.375e-007 0 0
3.75e-006 1.09375e-006 2.1875e-006 1.640625e-005 3.0859375e-005
4.38964844e-005 0.000112304687 0.000243164063 0.000433181763 0.00170898437
0.00272619247 0.00518844604 0.000352621078 0.00175960064 0.027875185
0.0351329803 0.103964925
*/
static double binary_search(const SkDCubic& cubic, double step, const SkDPoint& pt, double t,
int* iters) {
double firstStep = step;
do {
*iters += 1;
SkDPoint cubicAtT = cubic.ptAtT(t);
if (cubicAtT.approximatelyEqual(pt)) {
break;
}
double calcX = cubicAtT.fX - pt.fX;
double calcY = cubicAtT.fY - pt.fY;
double calcDist = calcX * calcX + calcY * calcY;
if (step == 0) {
SkDebugf("binary search failed: step=%1.9g cubic=", firstStep);
cubic.dump();
SkDebugf(" t=%1.9g ", t);
pt.dump();
SkDebugf("\n");
return -1;
}
double lastStep = step;
step /= 2;
SkDPoint lessPt = cubic.ptAtT(t - lastStep);
double lessX = lessPt.fX - pt.fX;
double lessY = lessPt.fY - pt.fY;
double lessDist = lessX * lessX + lessY * lessY;
// use larger x/y difference to choose step
if (calcDist > lessDist) {
t -= step;
t = SkTMax(0., t);
} else {
SkDPoint morePt = cubic.ptAtT(t + lastStep);
double moreX = morePt.fX - pt.fX;
double moreY = morePt.fY - pt.fY;
double moreDist = moreX * moreX + moreY * moreY;
if (calcDist <= moreDist) {
continue;
}
t += step;
t = SkTMin(1., t);
}
} while (true);
return t;
}
#if 0
static bool r2check(double A, double B, double C, double D, double* R2MinusQ3Ptr) {
if (approximately_zero(A)
&& approximately_zero_when_compared_to(A, B)
&& approximately_zero_when_compared_to(A, C)
&& approximately_zero_when_compared_to(A, D)) { // we're just a quadratic
return false;
}
if (approximately_zero_when_compared_to(D, A)
&& approximately_zero_when_compared_to(D, B)
&& approximately_zero_when_compared_to(D, C)) { // 0 is one root
return false;
}
if (approximately_zero(A + B + C + D)) { // 1 is one root
return false;
}
double a, b, c;
{
double invA = 1 / A;
a = B * invA;
b = C * invA;
c = D * invA;
}
double a2 = a * a;
double Q = (a2 - b * 3) / 9;
double R = (2 * a2 * a - 9 * a * b + 27 * c) / 54;
double R2 = R * R;
double Q3 = Q * Q * Q;
double R2MinusQ3 = R2 - Q3;
*R2MinusQ3Ptr = R2MinusQ3;
return true;
}
#endif
/* What is the relationship between the accuracy of the root in range and the magnitude of all
roots? To find out, create a bunch of cubics, and measure */
DEF_TEST(PathOpsCubicLineRoots, reporter) {
if (!gPathOpsCubicLineIntersectionIdeasVerbose) { // slow; exclude it by default
return;
}
SkRandom ran;
double worstStep[256] = {0};
int errors = 0;
int iters = 0;
double smallestR2 = 0;
double largestR2 = 0;
for (int index = 0; index < 1000000000; ++index) {
SkDPoint origin = {ran.nextRangeF(-1000, 1000), ran.nextRangeF(-1000, 1000)};
CubicPts cuPts = {{origin,
{ran.nextRangeF(-1000, 1000), ran.nextRangeF(-1000, 1000)},
{ran.nextRangeF(-1000, 1000), ran.nextRangeF(-1000, 1000)},
{ran.nextRangeF(-1000, 1000), ran.nextRangeF(-1000, 1000)}
}};
// construct a line at a known intersection
double t = ran.nextRangeF(0, 1);
SkDCubic cubic;
cubic.debugSet(cuPts.fPts);
SkDPoint pt = cubic.ptAtT(t);
// skip answers with no intersections (although note the bug!) or two, or more
// see if the line / cubic has a fun range of roots
double A, B, C, D;
SkDCubic::Coefficients(&cubic[0].fY, &A, &B, &C, &D);
D -= pt.fY;
double allRoots[3] = {0}, validRoots[3] = {0};
int realRoots = SkDCubic::RootsReal(A, B, C, D, allRoots);
int valid = SkDQuad::AddValidTs(allRoots, realRoots, validRoots);
if (valid != 1) {
continue;
}
if (realRoots == 1) {
continue;
}
t = validRoots[0];
SkDPoint calcPt = cubic.ptAtT(t);
if (calcPt.approximatelyEqual(pt)) {
continue;
}
#if 0
double R2MinusQ3;
if (r2check(A, B, C, D, &R2MinusQ3)) {
smallestR2 = SkTMin(smallestR2, R2MinusQ3);
largestR2 = SkTMax(largestR2, R2MinusQ3);
}
#endif
double largest = SkTMax(fabs(allRoots[0]), fabs(allRoots[1]));
if (realRoots == 3) {
largest = SkTMax(largest, fabs(allRoots[2]));
}
int largeBits;
if (largest <= 1) {
#if 0
SkDebugf("realRoots=%d (%1.9g, %1.9g, %1.9g) valid=%d (%1.9g, %1.9g, %1.9g)\n",
realRoots, allRoots[0], allRoots[1], allRoots[2], valid, validRoots[0],
validRoots[1], validRoots[2]);
#endif
double smallest = SkTMin(allRoots[0], allRoots[1]);
if (realRoots == 3) {
smallest = SkTMin(smallest, allRoots[2]);
}
SkASSERT_RELEASE(smallest < 0);
SkASSERT_RELEASE(smallest >= -1);
largeBits = 0;
} else {
frexp(largest, &largeBits);
SkASSERT_RELEASE(largeBits >= 0);
SkASSERT_RELEASE(largeBits < 256);
}
double step = 1e-6;
if (largeBits > 21) {
step = 1e-1;
} else if (largeBits > 18) {
step = 1e-2;
} else if (largeBits > 15) {
step = 1e-3;
} else if (largeBits > 12) {
step = 1e-4;
} else if (largeBits > 9) {
step = 1e-5;
}
double diff;
do {
double newT = binary_search(cubic, step, pt, t, &iters);
if (newT >= 0) {
diff = fabs(t - newT);
break;
}
step *= 1.5;
SkASSERT_RELEASE(step < 1);
} while (true);
worstStep[largeBits] = SkTMax(worstStep[largeBits], diff);
#if 0
{
cubic.dump();
SkDebugf("\n");
SkDLine line = {{{pt.fX - 1, pt.fY}, {pt.fX + 1, pt.fY}}};
line.dump();
SkDebugf("\n");
}
#endif
++errors;
}
SkDebugf("errors=%d avgIter=%1.9g", errors, (double) iters / errors);
SkDebugf(" steps: ");
int worstLimit = SK_ARRAY_COUNT(worstStep);
while (worstStep[--worstLimit] == 0) ;
for (int idx2 = 0; idx2 <= worstLimit; ++idx2) {
SkDebugf("%1.9g ", worstStep[idx2]);
}
SkDebugf("\n");
SkDebugf("smallestR2=%1.9g largestR2=%1.9g\n", smallestR2, largestR2);
}
static double testOneFailure(const CubicLineFailures& failure) {
const CubicPts& c = failure.c;
SkDCubic cubic;
cubic.debugSet(c.fPts);
const SkDPoint& pt = failure.p;
double A, B, C, D;
SkDCubic::Coefficients(&cubic[0].fY, &A, &B, &C, &D);
D -= pt.fY;
double allRoots[3] = {0}, validRoots[3] = {0};
int realRoots = SkDCubic::RootsReal(A, B, C, D, allRoots);
int valid = SkDQuad::AddValidTs(allRoots, realRoots, validRoots);
SkASSERT_RELEASE(valid == 1);
SkASSERT_RELEASE(realRoots != 1);
double t = validRoots[0];
SkDPoint calcPt = cubic.ptAtT(t);
SkASSERT_RELEASE(!calcPt.approximatelyEqual(pt));
int iters = 0;
double newT = binary_search(cubic, 0.1, pt, t, &iters);
return newT;
}
DEF_TEST(PathOpsCubicLineFailures, reporter) {
return; // disable for now
for (int index = 0; index < cubicLineFailuresCount; ++index) {
const CubicLineFailures& failure = cubicLineFailures[index];
double newT = testOneFailure(failure);
SkASSERT_RELEASE(newT >= 0);
}
}
DEF_TEST(PathOpsCubicLineOneFailure, reporter) {
return; // disable for now
const CubicLineFailures& failure = cubicLineFailures[1];
double newT = testOneFailure(failure);
SkASSERT_RELEASE(newT >= 0);
}
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