code: public static void addRowTimes(Matrix matrix, long diag, long fromCol, long row, double factor) {
  		long cols = matrix.getColumnCount();
  		for (long col = fromCol; col < cols; col++) {
  			matrix.setAsDouble(
  					matrix.getAsDouble(row, col) - factor * matrix.getAsDouble(diag, col), row, col);
  		}
  	}
docs: Add a factor times one row to another row
  
  @param matrix
  the matrix to modify
  @param diag
  coordinate on the diagonal
  @param fromCol
  first column to process
  @param row
  row to process
  @param factor
  factor to multiply