64   PetscReal          lambda, lambdatemp, lambdaprev, minlambda, initslope, alpha, stol;  in SNESLineSearchApply_BT()  local
77   PetscCall(SNESLineSearchGetLambda(linesearch, &lambda));  in SNESLineSearchApply_BT()
131     PetscCall(VecWAXPY(W, -lambda, Y, X));  in SNESLineSearchApply_BT()
157 …search: objective function at lambdas = %g is infinity or NaN, cutting lambda\n", (double)lambda));  in SNESLineSearchApply_BT()
160     if (lambda <= minlambda) SNESCheckFunctionDomainError(snes, g);  in SNESLineSearchApply_BT()
161     lambda *= .5;  in SNESLineSearchApply_BT()
165 …if (g <= f + lambda * alpha * initslope) { /* Sufficient reduction or step tolerance convergence */  in SNESLineSearchApply_BT()
188     lambdaprev = lambda;  in SNESLineSearchApply_BT()
192       lambdatemp = -initslope * PetscSqr(lambda) / (2.0 * (g - f - lambda * initslope));  in SNESLineSearchApply_BT()
193       lambda     = PetscClipInterval(lambdatemp, .1 * lambda, .5 * lambda);  in SNESLineSearchApply_BT()
195       PetscCall(VecWAXPY(W, -lambda, Y, X));  in SNESLineSearchApply_BT()
232 …if (linesearch->order != SNES_LINESEARCH_ORDER_LINEAR && g <= f + lambda * alpha * initslope) { /*…  in SNESLineSearchApply_BT()
235 …intf(monitor, "    Line search: Quadratically determined step, lambda=%18.16e\n", (double)lambda));  in SNESLineSearchApply_BT()
240         if (lambda <= minlambda) {  in SNESLineSearchApply_BT()
245 … (double)fnorm, (double)gnorm, (double)ynorm, (double)minlambda, (double)lambda, (double)initslope…  in SNESLineSearchApply_BT()
247 ….16e\n", (double)f, (double)g, (double)ynorm, (double)minlambda, (double)lambda, (double)initslope…  in SNESLineSearchApply_BT()
256           t1 = g - f - lambda * initslope;  in SNESLineSearchApply_BT()
258           a  = (t1 / (lambda * lambda) - t2 / (lambdaprev * lambdaprev)) / (lambda - lambdaprev);  in SNESLineSearchApply_BT()
259 …b  = (-lambdaprev * t1 / (lambda * lambda) + lambda * t2 / (lambdaprev * lambdaprev)) / (lambda - …  in SNESLineSearchApply_BT()
265           lambdatemp = -initslope * PetscSqr(lambda) / (2.0 * (g - f - lambda * initslope));  in SNESLineSearchApply_BT()
267           lambdatemp = .5 * lambda;  in SNESLineSearchApply_BT()
269         lambdaprev = lambda;  in SNESLineSearchApply_BT()
272         lambda = PetscClipInterval(lambdatemp, .1 * lambda, .5 * lambda);  in SNESLineSearchApply_BT()
273         PetscCall(VecWAXPY(W, -lambda, Y, X));  in SNESLineSearchApply_BT()
277 …l slope=%18.16e\n", (double)fnorm, (double)gnorm, (double)ynorm, (double)lambda, (double)initslope…  in SNESLineSearchApply_BT()
296         if (g <= f + lambda * alpha * initslope) { /* is reduction enough? */  in SNESLineSearchApply_BT()
300 …nt gnorm %14.12e lambda=%18.16e\n", ordStr[linesearch->order - 1], (double)gnorm, (double)lambda));  in SNESLineSearchApply_BT()
303 …%s step, obj %14.12e lambda=%18.16e\n", ordStr[linesearch->order - 1], (double)g, (double)lambda));  in SNESLineSearchApply_BT()
311 …nt gnorm %12.12e lambda=%18.16e\n", ordStr[linesearch->order - 1], (double)gnorm, (double)lambda));  in SNESLineSearchApply_BT()
314 … lambda, obj %12.12e lambda=%18.16e\n", ordStr[linesearch->order - 1], (double)g, (double)lambda));  in SNESLineSearchApply_BT()
323   PetscCall(SNESLineSearchSetLambda(linesearch, lambda));  in SNESLineSearchApply_BT()
326     if (!changed_w) PetscCall(VecWAXPY(W, -lambda, Y, X));  in SNESLineSearchApply_BT()