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Relax the requirements on loss functiond derivatives.

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We now require that the first derivative of the loss function
be positive only if the second derivative is non-zero. This is
because when the second derivative is non-positive, we do not use
the second order correction suggested by BANS and instead use
a simpler first order strategy which does not use a division by
the gradient of the loss function.

Change-Id: I3d65713f152611998e196ff389a7081acfdfd8c1
This commit is contained in:
Sameer Agarwal
2013-11-19 10:12:05 -08:00
parent db98425b94
commit 54fcbf8938
1 changed files with 8 additions and 1 deletions
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internal/ceres/corrector.cc
+8 -1
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@@ -40,7 +40,6 @@ namespace internal {
Corrector::Corrector(const double sq_norm, const double rho[3]) {
CHECK_GE(sq_norm, 0.0);
CHECK_GT(rho[1], 0.0);
sqrt_rho1_ = sqrt(rho[1]);
// If sq_norm = 0.0, the correction becomes trivial, the residual
@@ -85,6 +84,14 @@ Corrector::Corrector(const double sq_norm, const double rho[3]) {
return;
}
// We now require that the first derivative of the loss function be
// positive only if the second derivative is non-zero. This is
// because when the second derivative is non-positive, we do not use
// the second order correction suggested by BANS and instead use a
// simpler first order strategy which does not use a division by the
// gradient of the loss function.
CHECK_GT(rho[1], 0.0);
// Calculate the smaller of the two solutions to the equation
//
// 0.5 * alpha^2 - alpha - rho'' / rho' * z'z = 0.