[SYSTEMML-2130] Extended sparse block validation for COO format

Closes apache#735.

src/main/java/org/apache/sysml/runtime/matrix/data/SparseBlockCOO.java

@@ -194,7 +194,50 @@ public boolean isAllocated(int r) {
 
 	@Override
 	public boolean checkValidity(int rlen, int clen, long nnz, boolean strict) {
-		//empty implementation
+		//1. correct meta data
+		if(rlen < 0 || clen < 0) {
+			throw new RuntimeException("Invalid block dimensions: "+rlen+" "+clen);
+		}
+
+		//2. correct array lengths
+		if(_size != nnz && _cindexes.length < nnz && _rindexes.length < nnz && _values.length < nnz) {
+			throw new RuntimeException("Incorrect array lengths.");
+		}
+
+		//3.1. sort order of row indices
+		for( int i=1; i<=nnz; i++ ) {
+			if(_rindexes[i] < _rindexes[i-1])
+				throw new RuntimeException("Wrong sorted order of row indices");
+		}
+
+		//3.2. sorted values wrt to col indexes wrt to a given row index
+		for( int i=0; i<rlen; i++ ) {
+			int apos = pos(i);
+			int alen = size(i);
+			for(int k=apos+i; k<apos+alen; k++)
+				if( _cindexes[k+1] >= _cindexes[k] )
+					throw new RuntimeException("Wrong sparse row ordering: "
+							+ k + " "+_cindexes[k-1]+" "+_cindexes[k]);
+			for( int k=apos; k<apos+alen; k++ )
+				if(_values[k] == 0)
+					throw new RuntimeException("Wrong sparse row: zero at "
+							+ k + " at col index " + _cindexes[k]);
+		}
+
+		//4. non-existing zero values
+		for( int i=0; i<_size; i++ ) {
+			if( _values[i] == 0)
+				throw new RuntimeException("The values array should not contain zeros."
+						+ " The " + i + "th value is "+_values[i]);
+		}
+
+		//5. a capacity that is no larger than nnz times the resize factor
+		int capacity = _values.length;
+		if( capacity > nnz*RESIZE_FACTOR1 ) {
+			throw new RuntimeException("Capacity is larger than the nnz times a resize factor."
+					+ " Current size: "+capacity+ ", while Expected size:"+nnz*RESIZE_FACTOR1);
+		}
+
 		return true;
 	}