Make whitening tests work on hosted macs (dotnet#1530)

Author: artidoro

.vsts-dotnet-ci.yml

@@ -36,4 +36,4 @@ phases:
     name: MacOS
     buildScript: ./build.sh
     queue:
-      name: DotNetCore-Mac
+      name: Hosted macOS

build.proj

@@ -75,12 +75,6 @@
     <MSBuild Projects="@(PkgProject)"
              Targets="Pack" />
   </Target>
-
-  <ItemGroup>
-    <TestFile Include="$(MSBuildThisFileDirectory)/test/data/external/winequality-white.csv"
-      Url="https://archive.ics.uci.edu/ml/machine-learning-databases/wine-quality/winequality-white.csv"
-      DestinationFile="$(MSBuildThisFileDirectory)test/data/external/winequality-white.csv" />    
-  </ItemGroup>
 
   <ItemGroup Condition="'$(IncludeBenchmarkData)' == 'true'">
     <BenchmarkFile Update="@(BenchmarkFile)">

build/ci/phase-template.yml

@@ -22,8 +22,8 @@ phases:
     - script: $(_buildScript) -$(_configuration) -buildArch=$(_arch)
       displayName: Build
     - ${{ if eq(parameters.name, 'MacOS') }}:
-      - script: brew install libomp
-        displayName: Install OpenMP runtime dependency
+      - script: brew install libomp mono-libgdiplus gettext && brew link gettext --force
+        displayName: Install runtime dependencies
     - script: $(_buildScript) -$(_configuration) -runtests
       displayName: Run Tests
     - task: PublishTestResults@2

src/Microsoft.ML.Transforms/WhiteningTransform.cs

@@ -331,6 +331,15 @@ private void TrainModels(Float[][] columnData, int[] rowCounts, IChannel ch)
                 int crow = rowCounts[iinfo];
                 int ccol = Infos[iinfo].TypeSrc.ValueCount;
 
+                // If there is no training data, simply initialize the model matrices.
+                if (crow == 0)
+                {
+                    var matrixSize = ccol * ccol;
+                    _models[iinfo] = new float[matrixSize];
+                    InvModels[iinfo] = new float[matrixSize];
+                    continue;
+                }
+
                 // Compute covariance matrix (sigma).
                 var u = new Float[ccol * ccol];
                 ch.Info("Computing covariance matrix...");