code: public double subtract(int[] indices, double val) {
          checkIndices(indices);
          int c = getConfigIdx(indices);
          return values.set(c, s.minus(values.get(c), val));
      }
docs: Subtracts the value to the entry corresponding to the given indices.
  @param indices The indices of the multi-dimensional array.
  @param val The value to subtract.
  @return The previous value.