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Improve further the accuracy of JacobiSVD wrt under/overflow while improving speed for small matrices (hypot is very slow).

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This commit is contained in:
Gael Guennebaud 2014-09-10 23:11:58 +02:00
parent 2d90484450
commit 5e890d3ad7
2 changed files with 35 additions and 11 deletions
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17
Eigen/src/SVD/JacobiSVD.h
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@ -425,18 +425,19 @@ void real_2x2_jacobi_svd(const MatrixType& matrix, Index p, Index q,
JacobiRotation<RealScalar> rot1;
RealScalar t = m.coeff(0,0) + m.coeff(1,1);
RealScalar d = m.coeff(1,0) - m.coeff(0,1);
if(t == RealScalar(0))
if(d == RealScalar(0))
{
rot1.c() = RealScalar(0);
rot1.s() = d > RealScalar(0) ? RealScalar(1) : RealScalar(-1);
rot1.s() = RealScalar(0);
rot1.c() = RealScalar(1);
}
else
{
RealScalar t2d2 = numext::hypot(t,d);
rot1.c() = abs(t)/t2d2;
rot1.s() = d/t2d2;
if(t<RealScalar(0))
rot1.s() = -rot1.s();
// If d!=0, then t/d cannot overflow because the magnitude of the
// entries forming d are not too small compared to the ones forming t.
RealScalar u = t / d;
rot1.s() = RealScalar(1) / sqrt(RealScalar(1) + numext::abs2(u));
rot1.c() = rot1.s() * u;
}
m.applyOnTheLeft(0,1,rot1);
j_right->makeJacobi(m,0,1);

29
test/jacobisvd.cpp
View File

@ -354,11 +354,33 @@ void jacobisvd_underoverflow()
Matrix2d M;
M << -7.90884e-313, -4.94e-324,
0, 5.60844e-313;
JacobiSVD<Matrix2d> svd;
svd.compute(M,ComputeFullU|ComputeFullV);
jacobisvd_check_full(M,svd);
VectorXd value_set(9);
value_set << 0, 1, -1, 5.60844e-313, -5.60844e-313, 4.94e-324, -4.94e-324, -4.94e-223, 4.94e-223;
Array4i id(0,0,0,0);
int k = 0;
do
{
M << value_set(id(0)), value_set(id(1)), value_set(id(2)), value_set(id(3));
svd.compute(M,ComputeFullU|ComputeFullV);
jacobisvd_check_full(M,svd);
id(k)++;
if(id(k)>=value_set.size())
{
while(k<3 && id(k)>=value_set.size()) id(++k)++;
id.head(k).setZero();
k=0;
}
} while((id<int(value_set.size())).all());
#if defined __INTEL_COMPILER
#pragma warning pop
#endif
JacobiSVD<Matrix2d> svd;
svd.compute(M); // just check we don't loop indefinitely
// Check for overflow:
Matrix3d M3;
@ -367,7 +389,8 @@ void jacobisvd_underoverflow()
-8.7190887618028355e+307, -7.3453213709232193e+307, -2.4367363684472105e+307;
JacobiSVD<Matrix3d> svd3;
svd3.compute(M3); // just check we don't loop indefinitely
svd3.compute(M3,ComputeFullU|ComputeFullV); // just check we don't loop indefinitely
jacobisvd_check_full(M3,svd3);
}
void jacobisvd_preallocate()