[SYSTEMDS-3805] Fix scalar right indexing (only for valid indices)

In order to ensure consistent error handling, we now only use the
scalar right indexing if the index-range is within the matrix dims.

Author: mboehm7

src/main/java/org/apache/sysds/runtime/instructions/cp/MatrixIndexingCPInstruction.java

@@ -50,7 +50,7 @@ protected MatrixIndexingCPInstruction(CPOperand lhsInput, CPOperand rhsInput, CP
 	@Override
 	public void processInstruction(ExecutionContext ec) {
 		String opcode = getOpcode();
-		IndexRange ixrange = getIndexRange(ec);
+		IndexRange ix = getIndexRange(ec);
 
 		//get original matrix
 		MatrixObject mo = ec.getMatrixObject(input1.getName());
@@ -61,19 +61,19 @@ public void processInstruction(ExecutionContext ec) {
 			MatrixBlock resultBlock = null;
 
 			if( mo.isPartitioned() ) //via data partitioning
-				resultBlock = mo.readMatrixPartition(ixrange.add(1));
-			else if( ixrange.isScalar() ){
+				resultBlock = mo.readMatrixPartition(ix.add(1));
+			else if( ix.isScalar() && ix.rowStart < mo.getNumRows() && ix.colStart < mo.getNumColumns() ) {
 				MatrixBlock matBlock = mo.acquireReadAndRelease();
 				resultBlock = new MatrixBlock(
-					matBlock.get((int)ixrange.rowStart, (int)ixrange.colStart));
+					matBlock.get((int)ix.rowStart, (int)ix.colStart));
 			}
 			else //via slicing the in-memory matrix
 			{
 				//execute right indexing operation (with shallow row copies for range
 				//of entire sparse rows, which is safe due to copy on update)
 				MatrixBlock matBlock = mo.acquireRead();
-				resultBlock = matBlock.slice((int)ixrange.rowStart, (int)ixrange.rowEnd, 
-					(int)ixrange.colStart, (int)ixrange.colEnd, false, new MatrixBlock());
+				resultBlock = matBlock.slice((int)ix.rowStart, (int)ix.rowEnd, 
+					(int)ix.colStart, (int)ix.colEnd, false, new MatrixBlock());
 
 				//unpin rhs input
 				ec.releaseMatrixInput(input1.getName());
@@ -101,15 +101,15 @@ else if ( opcode.equalsIgnoreCase(LeftIndex.OPCODE))
 
 			if(input2.getDataType() == DataType.MATRIX) { //MATRIX<-MATRIX
 				MatrixBlock rhsMatBlock = ec.getMatrixInput(input2.getName());
-				resultBlock = matBlock.leftIndexingOperations(rhsMatBlock, ixrange, new MatrixBlock(), updateType);
+				resultBlock = matBlock.leftIndexingOperations(rhsMatBlock, ix, new MatrixBlock(), updateType);
 				ec.releaseMatrixInput(input2.getName());
 			}
 			else { //MATRIX<-SCALAR 
-				if(!ixrange.isScalar())
-					throw new DMLRuntimeException("Invalid index range of scalar leftindexing: "+ixrange.toString()+"." );
+				if(!ix.isScalar())
+					throw new DMLRuntimeException("Invalid index range of scalar leftindexing: "+ix.toString()+"." );
 				ScalarObject scalar = ec.getScalarInput(input2.getName(), ValueType.FP64, input2.isLiteral());
 				resultBlock = matBlock.leftIndexingOperations(scalar, 
-					(int)ixrange.rowStart, (int)ixrange.colStart, new MatrixBlock(), updateType);
+					(int)ix.rowStart, (int)ix.colStart, new MatrixBlock(), updateType);
 			}
 
 			//unpin lhs input