Refactoring of Constructors

[abgoswam]

Currently in our codebase, we have two constructors that are used for initialization of the underlying object.

Example:

A.

machinelearning/src/Microsoft.ML.FastTree/FastTreeRanking.cs

Lines 75 to 84 in bdc9a9e

	public FastTreeRankingTrainer(IHostEnvironment env,
	string labelColumn = DefaultColumnNames.Label,
	string featureColumn = DefaultColumnNames.Features,
	string groupIdColumn = DefaultColumnNames.GroupId,
	string weightColumn = null,
	int numLeaves = Defaults.NumLeaves,
	int numTrees = Defaults.NumTrees,
	int minDatapointsInLeaves = Defaults.MinDocumentsInLeaves,
	double learningRate = Defaults.LearningRates,
	Action<Arguments> advancedSettings = null)

B.

machinelearning/src/Microsoft.ML.FastTree/FastTreeRanking.cs

Lines 93 to 95 in bdc9a9e

	internal FastTreeRankingTrainer(IHostEnvironment env, Arguments args)
	: base(env, args, TrainerUtils.MakeR4ScalarColumn(args.LabelColumn))
	{

We need to bringing the public API surface to the desired shape. As such, we are making both constructors internal, and fixing other issues with the public API as outlined in #1798.

Additionally, constructor (B) has all the details for constructing the underlying object. As such, we can delete constructor (A) altogether.

NOTE: We will do this issue only after finishing the work to bring public API to the desired shape .

Constructors that need closer look towards unification:

SdcaBinaryTrainer
SdcaMultiClassTrainer
SdcaRegressionTrainer
StochasticGradientDescentClassificationTrainer
FastTreeRankingTrainer
FastTreeRegressionTrainer
FastTreeBinaryClassificationTrainer
FastForestClassification
FastForestRegression
PoissonRegression
LogisticRegression
BinaryClassificationGamTrainer
LightGbmBinaryTrainer
LightGbmMulticlassTrainer
LightGbmRankingTrainer
LightGbmRegressorTrainer

@TomFinley @glebuk @shauheen @sfilipi @artidoro @rogancarr

[TomFinley]

Good, so #1098 will be "the way" unambiguously for the public API, I guess, for v1.

[abgoswam]

Yeap. That is why as part of the work for #1798 we are making the constructors internal.