[SYSTEMDS-3853] Fix ampute outer broadcasting and error handling

This patch fixes an invalid left-hand-side and left- and right-hand-side
broadcasting in the new ampute builtin function. We now have a proper
error handling in the hop to guide script developers that broadcasts
can only be used from the right-hand-side.

Author: mboehm7

scripts/builtin/ampute.dml

@@ -72,8 +72,8 @@ m_ampute = function(Matrix[Double] X,
 
       # 4. Use probabilities to ampute pattern candidates:
       random = rand(rows=groupSize, cols=1, min=0, max=1, pdf="uniform", seed=seed)
-      amputeds = (random <= probs) * (1 - patterns[patternNum]) # Obtains matrix with 1's at indices to ampute.
-      while (FALSE) {} # FIX ME
+      # Obtains matrix with 1's at indices to ampute.
+      amputeds = outer((random <= probs), (1 - patterns[patternNum]), "*")
       groupSamples = groupSamples + replace(target=amputeds, pattern=1, replacement=NaN)
 
       # 5. Update output matrix:
@@ -241,7 +241,6 @@ return (Matrix[Double] groupAssignments, Matrix[Double] groupCounts) {
 
     for (i in 1:numGroups) {
       assigned = (random >= cumSum[i]) & (random < cumSum[i + 1])
-      while (FALSE) {} # FIX ME
       groupCounts[i] = sum(assigned)
       groupAssignments = groupAssignments + i * assigned
     }
@@ -308,4 +307,4 @@ return(Integer start, Integer end) {
     start = sum(numPerGroup[1:(patternNum - 1), ]) + 1
   }
   end = start + groupSize - 1
-}
+}

src/main/java/org/apache/sysds/hops/BinaryOp.java

@@ -1092,6 +1092,15 @@ else if( dt1 == DataType.SCALAR && dt2 == DataType.MATRIX  )
 					}
 					else //GENERAL CASE
 					{
+						//check correct broadcasting dimensions
+						if( (input1.getDim1()==1 && input2.getDim1() > 1)
+							|| (input1.getDim2()==1 && input2.getDim2() > 1) )
+						{
+							throw new HopsException("Invalid binary broadcasting from left: "
+								+ input1.getDataCharacteristics()+" "+getOp().name()+" "
+								+input2.getDataCharacteristics());
+						}
+						
 						ldim1 = (input1.rowsKnown()) ? input1.getDim1()
 							: ((input2.getDim1()>1)?input2.getDim1():-1);
 						ldim2 = (input1.colsKnown()) ? input1.getDim2()