Add Seed property to MLContext and use as default for data splits

[najeeb-kazmi]

Fixes #4752

Addresses leftover feedback from #4764

[najeeb-kazmi]

            Random rand = (seed.HasValue) ? RandomUtils.Create(seed.Value) : RandomUtils.Create(_rand);

Should this just use _rand here rather than creating another TauswortheHybrid from _rand?

---

Refers to: src/Microsoft.ML.Core/Environment/HostEnvironmentBase.cs:394 in 9bbccaf. [](commit_id = 9bbccaf, deletion_comment = False)

[najeeb-kazmi]

                Random rand = (seed.HasValue) ? RandomUtils.Create(seed.Value) : RandomUtils.Create(_rand);

Should HostBase use the same TauswortheHybrid as the parent environment or create another one using the parent _rand as seed?

---

Refers to: src/Microsoft.ML.Core/Environment/HostEnvironmentBase.cs:136 in 9bbccaf. [](commit_id = 9bbccaf, deletion_comment = False)

[mstfbl]

The CI builds are giving the following errors:

2020-02-04T02:22:45.6483640Z /__w/1/s/packages/microsoft.dotnet.apicompat/1.0.0-beta.19225.5/build/Microsoft.DotNet.ApiCompat.targets(72,5): error : InterfacesShouldHaveSameMembers : Interface member 'Microsoft.ML.Runtime.IHostEnvironment.Seed' is present in the implementation but not in the contract. [/__w/1/s/src/Microsoft.ML.Core/Microsoft.ML.Core.csproj]
2020-02-04T02:22:45.6484602Z /__w/1/s/packages/microsoft.dotnet.apicompat/1.0.0-beta.19225.5/build/Microsoft.DotNet.ApiCompat.targets(72,5): error : InterfacesShouldHaveSameMembers : Interface member 'Microsoft.ML.Runtime.IHostEnvironment.Seed.get()' is present in the implementation but not in the contract. [/__w/1/s/src/Microsoft.ML.Core/Microsoft.ML.Core.csproj]

Perhaps you are forgetting to declare int Seed and Seed's get() function somewhere?

[eerhardt]

The CI builds are giving the following errors:

2020-02-04T02:22:45.6483640Z /__w/1/s/packages/microsoft.dotnet.apicompat/1.0.0-beta.19225.5/build/Microsoft.DotNet.ApiCompat.targets(72,5): error : InterfacesShouldHaveSameMembers : Interface member 'Microsoft.ML.Runtime.IHostEnvironment.Seed' is present in the implementation but not in the contract. [/__w/1/s/src/Microsoft.ML.Core/Microsoft.ML.Core.csproj]

This is because you are adding a member to an interface, which is a breaking change. Interfaces, once shipped, can't be changed. #Resolved

[yaeldekel]

env.Seed [](start = 135, length = 8)

This can also be null, can't it? #Resolved

[najeeb-kazmi]

Yes, if env.Seed is also null, it will fall back to the HashingEstimator default seed:

machinelearning/src/Microsoft.ML.Data/Transforms/Hashing.cs

Lines 1129 to 1132 in 46e7dc6

	internal static class Defaults
	{
	public const int NumberOfBits = NumBitsLim - 1;
	public const uint Seed = 314489979;

#Resolved

[yaeldekel]

But you are casting it to uint here. If it's null it will throw an exception.

---

In reply to: 375521058 [](ancestors = 375521058)

[najeeb-kazmi]

Ah yes, you're right. Thanks for catching that @yaeldekel. I've changed the handling back to how it was before I added (uint)(seed ?? host.Rand.Next()) and added a case to handle seed from the environment. Order of precedence for seed now is (1) user specified to TrainTestSplit/CrossValidata, (2) MLContext seed, (3) default seed for HashingEstimator #Resolved

[justinormont]

LGTM.

[harishsk]