2018-03-18  Tuomo Keskitalo  <tuomo.keskitalo@iki.fi>

	* rk2imp.c and evolve.c: Added debug printouts, run indent -gnu -nut.

	Thanks for Dominic Steinitz for the additions!

	* test.c: Added identifiers to debug printouts.

2017-11-04  Tuomo Keskitalo  <tuomo.keskitalo@iki.fi>

	* cscal.c: Corrected bug #52336 in cscal.c: Decreased maximum step

	length increase coefficient (now named maxscale) from 5.0 to 4.9

	because value of 5.0 hits a singularity in msbdf stepper with

	order 3, causing a floating point exception. Thanks to Andrew

	Benson for reporting this bug!

2017-10-22  Tuomo Keskitalo  <tuomo.keskitalo@iki.fi>

	* msadams.c: Corrected bug #52230 in msadams_apply, where solver

	crashed to order change -2 error. This could happen in a very rare

	case when two consecutive failed steps suggest decreasing

	order. Fix is to reset solver if that happens. Thanks for Michael

	Kaufman for reporting this bug and testing the fix!

2013-06-08  Tuomo Keskitalo  <tuomo.keskitalo@iki.fi>

	* driver.c: Removed redundant if clause. Thanks to

	David Binderman for the report!

2013-01-27  Tuomo Keskitalo  <tuomo.keskitalo@iki.fi>

	* msbdf.c: Corrected bug which enabled order to be changed 

	by two (first by stability enhancement, then by order evaluation

	after a rejected step). Thanks for Frantisek Kluknavsky and

	Andreas Schwab for bug reports!

	* msbdf.c: Added more state variables explicitly to be reset in 

	msbdf_reset. 

	*msbdf.c: Added abscorscaled to remove division of abscor for 

	use in msbdf_eval_order and subsequent backwards multiplication.

	*test.c: test_extreme_problems: Increased ringmod case tolerances 

	from 1e-7 to 1e-12 to increase precision. Because that

	increases computational burden, I also decreased end time 

	from 1e-3 to 1e-5. That decreased the acidity of the test 

	significantly, but the test case is now more appropriate 

	for normal "make check". Thanks for Frantisek Kluknavsky

	for pointing out bad design of the test case.

2012-09-10  Rhys Ulerich  <rhys.ulerich@gmail.com>

	* test.c: Correct two out-of-order declarations.

	Thanks to Brian Gladman for spotting the problem.

2012-03-10  Tuomo Keskitalo  <tuomo.keskitalo@iki.fi>

	* driver.c: Added function gsl_odeiv2_driver_reset_hstart to

	allow resetting step size, possibly change its sign, too.

	Check for non-zero hstart in initializations.

	* test.c: Modified test_driver to carry out tests with all

	steppers. Small printout changes.

2012-01-21  Tuomo Keskitalo  <tuomo.keskitalo@iki.fi>

	* rkf45.c: Bug correction: Set gives_exact_dydt_out to 1 in

	rkf45_type

2012-01-14  Tuomo Keskitalo  <tuomo.keskitalo@iki.fi>

	* evolve.c: Modified initial derivative evaluation in evolve_apply

	to reuse previously calculated values. This saves calls to the

	user function. Thanks for Illes Farkas for pointing out redundant

	function calls!

2011-06-28  Brian Gough  <bjg@network-theory.co.uk>

	* rk4imp.c (rk4imp_apply): use M_SQRT3 instead of sqrt(3) in array

	initialiser.

2011-05-02  Brian Gough  <bjg@network-theory.co.uk>

	* gsl_odeiv2.h: fix header guard to __GSL_ODEIV2_H__

2011-05-01  Tuomo Keskitalo  <Tuomo.Keskitalo@iki.fi>

	* Replaced ChangeLog with contents of ode-initval2 development log

	file (ChangeLog-odeiv2_development) and reformatted the log file.

2010-10-16  Tuomo Keskitalo  <Tuomo.Keskitalo@iki.fi>

	* Modified evolve and driver so that when user function returns

	GSL_EBADFUNC, then ode-initval2 functions return immediately with

	that same return value.

	* Corrected bug in msadams for saving ordm1coeff to state. Thanks

	to Andrew Benson for pointing out this bug!

2010-10-10  Tuomo Keskitalo  <Tuomo.Keskitalo@iki.fi>

	* driver.c: Corrected error in driver_evolve_apply, integration to

	negative direction should work now.

	* Added evolve_apply_fixed_step and driver_apply_fixed_step for

	users who want to use a constant step size to evolve the system.

	* test.c: added test cases for driver (negative evolution,

	apply_fixed_step).

	* gsl_odeiv2.h: cleaning and add apply_fixed_step functions.

	* doc/ode-initval.texi: Replaced derivative apostrophe with \prime

	(because my new system fails to make ps otherwise). Added new

	documentation about apply_fixed_step functions.

2010-10-09  Tuomo Keskitalo  <Tuomo.Keskitalo@iki.fi>

	* ode-initval2 bzr development branch now at savannah:

	http://bzr.savannah.gnu.org/r/gsl/ode-initval2/

2010-01-02  Tuomo Keskitalo  <tuomo.keskitalo@iki.fi>

	* Changes from ode-initval2-0.9 to ode-initval2-1.0:

	* Removed set_control member from step object and added a

	set_driver member to evolve, control and step objects, so that the

	driver object and consequently evolve, control and step objects

	are all accessible from another. Currently only some steppers

	utilize this. They access the control_errlevel function via

	state->driver->c instead of state->control. This modification to

	the framework enables implementation of more efficient ODE

	solvers, which utilize communication among evolve, control and

	stepper objects. This also means that some steppers now require a

	driver object, and it is best to use those stepper methods through

	driver object functions.

	* cstd.c and cscal.c: Added a sanity check for errlev <= 0

	* run indent -gnu -nut for *.c *.h

	* driver.c: added function odeiv2_driver_alloc_standard_new and

	odeiv2_driver_alloc_yp_new

	* driver.c: changed n and nmax in driver struct to unsigned long

	int

	* modified documentation accordingly with small nomenclature

	changes and made year updates to source files

2009-11-01  Tuomo Keskitalo  <tuomo.keskitalo@iki.fi>

	* Merged with master and modified source to be published as a

	package for gsl-1.13.

2009-05-09  Tuomo Keskitalo  <tuomo.keskitalo@iki.fi>

	* Agreed with Brian Gough that the modification I've made cannot

	be incorporated to GSL until a major version number change, due to

	changes in API.

	* Replated rk2imp with imprk2 and rk4imp with imprk4. Also renamed

	impeuler to rk1imp for consistency.

	* Deleted steppers that are deprecated considering new major

	release: gear1, gear2, and rk2simp. Modified test.c accordingly.

2009-05-01  Tuomo Keskitalo  <tuomo.keskitalo@iki.fi>

	* Merged with master (evolve.c and test.c needed some manual

	work).

	* driver.c: Modified alloc-functions to minimal interface, added

	set_hmax, set_nmax and set_hmin functions.

	* test.c: Added test for minimum allowed step size.

	Applied indent -gnu -nut.

	* doc/ode-initval.texi: Updated documentation, added Driver

	section, updated examples.

2009-04-05  Tuomo Keskitalo  <tuomo.keskitalo@iki.fi>

	* Several uninitialized variable corrections from Brian Gough

	added

	* modnewton1, impeuler, imprk2, imprk4: removed unneeded arguments

	from solve and init

	* msadams and msbdf modifications:

	* added ordprevbackup, ordwaitbackup (backups) and failcount (to

	detect repeated steps rejections).

	* added checks to make sure order is not changed by more than one

	order. Added sanity check to catch it.

	* corrected failure and rejection handling for first step

	* Added a heuristic stability enhancement for msbdf. This is yet

	to be tested in practice.

	* test.c: Added more benchmark test cases. The results seem

	sensible.

	* test.c: Note for benchmark_precision: msbdf performs badly in

	rhs_func_exp. Newton iteration starts to fail to converge at some

	point, and this forces very small step sizes to be used. I

	currently think that this is not a bug, but that msbdf is just not

	suitable for this problem. I think that msbdf's prediction step

	does not give a good initial guess for Newton iteration in this

	case.

	* I tried to increase max_iter in msbdf from 3 to 7 (value used in

	modnewton1), and as a result, the performance was better for this

	case (Newton iteration convergence was better). However, I would

	not increase max_iter, because the default value of 3 is the value

	used by the authors in the references, and because it would

	decrease the efficiency of msbdf (method would use more function

	evaluations per step, and convergence might still not be

	achieved). It is best to useanother stepper in this kind of a

	case.

2009-02-28  Tuomo Keskitalo  <tuomo.keskitalo@iki.fi>

	* new stepper: msbdf. This is a variable-coefficient linear

	multistep backward differentiation formula (BDF) method in

	Nordsieck form. It appears to handle stiff cases well and it is

	efficient!

	* test.c: Ordered functions in file. Added extreme test case.

	* modnewton1: Convergence test now takes the desired error level

	via control object into account. Modified steppers that use

	modnewton1 accordingly.

	* modnewton1: Removed reuse_decomp. The variable was useless since

	iteration matrix is reconstructed at each stepper call.

	* modnewton1: Dropped max_iter from 10 to 7. Hairer and Wanner

	suggests a "relatively high number", but many iterations per step

	is costly.

	* steppers that use step doubling for error estimates: Introduced

	constant GSL_ODEIV_ERR_SAFETY in gsl_odeiv.h that is used to

	multiply the error estimates (yerr). This way user can modify this

	coefficient in one place if a change is wanted.

	* driver.c: This is a high level wrapper for ode-initval, which

	was wished for in TODO. Added test_driver to test.c to test it. Is

	this functionality enough?

	* ode-initval.texi: Added documentation for new steppers. Moved

	note about user error codes to system definition.

	* Some finetuning / code cleanup.

2009-01-21  Tuomo Keskitalo  <tuomo.keskitalo@iki.fi>

	* New explicit stepper: msadams (An explicit variable-coefficient

	linear multistep Adams method in Nordsieck form). Functional

	iteration is used to solve the non-linear equation system. The

	algorithms described in the references (see msadams.c) have been

	adapted to fit GSL odeiv framework. Currently this is beta, but

	the stepper now passes the odeiv test suite.

	* control.c, cstd.c, cscal.c: Added errlev function which

	calculates desired error level. This is used in masadams (and can

	be used in imp* steppers, too) to control accuracy of functional

	iteration. User must call gsl_odeiv_step_set_control after

	allocating step and control objects to pass the information about

	control object to stepper. This change (or something similar) is

	needed to pass tolerance for the stepper routines that need

	it. Modified stepper routines accordingly.

	* evolve.c: Changed the step length scaling coefficient for

	stepper failure from 0.1 to 0.5, because msadams seems to cope

	much better with this change in stiff[0,1] test case.

	* gsl_odeiv.h: gsl_odeiv_control and control_type introduced

	earlier because gsl_odeiv_step_type now refers to it.

2008-11-01  Tuomo Keskitalo  <tuomo.keskitalo@iki.fi>

	* New implicit solvers: imprk4 (replaces imprk42 in previous test

	package), imprk2 (replaces imprk21 in previous test package) and

	impeuler, which use modified Newton iteration to solve the

	implicit equations. I decided to dump imprk42 and imprk21 because

	I was unsure how to calculate the error estimates for them. I

	think that these new implicit methods could be used instead of

	rk4imp, rk2imp, gear2 and gear1, which use functional

	iteration (which is inefficient for stiff problems.) However, even

	these new solvers can not be used efficiently for truly nasty

	stiff problems, and better solvers are still needed.

	* modnewton1.c: a modified Newton solver for solution of

	non-linear equations of implicit solvers. Jacobian evaluation has

	been moved from modnewton1 to imprk2, imprk4 and impeuler.

	* evolve.c: modification to decrease step size if stepper fails,

	instead of giving up immediately.

	* evolve.c: A bug fix: Exit with GSL_FAILURE if step size reaches

	machine precision instead of continuing with old step size.

	* test.c: added Robertson stiff test

	* test.c: embedded test_oregonator to test_compare_stiff_probelms

	to test several stiff problems. Note: the tested integration

	interval is rather short due to inefficiency of solvers other than

	bsimp in these problems.

	* test.c: modified test_compare_vanderpol and

	test_compare_stiff_problems to check against results from first

	ode-solver. Changed rk4 or bsimp to first place.

	* test.c: modified stepfn and stepfn2 and expanded these to be

	tested with all explicit solvers

	* test.c: removed stepfn3 and added test_broken and

	test_stepsize_fail to check that evolve decreases step size below

	machine precision and exits with a failure code in the end if user

	functions fail continuously.

	* Changes in ode-initval.texi:

	* removed untrue sentence concerning stepping functions: "The

	step-size @var{h} will be set to the step-size which caused the

	error."

	* Changed gsl_odeiv_system variable name from dydt to sys for

	clarity

	* added "explicit" or "implicit" to stepper introductions for

	clarity

	* reformulated description of evolve_apply and step_apply and made

	changes to reflect the modifications to the code.

	* clarified the point on integrating over discontinuities. It is

	best to integrate in sequences.

	* removed the text suggesting the user to force a step size to

	integrate over the edge of a discontinuity. The applicability of

	this kind of a numerical tweak depends on the case, and should in

	my opinion not to be included in a reference book.