code: public void elemSubtract(VTensor other) {
          checkEqualSize(this, other);
          for (int c = 0; c < this.size(); c++) {
              subtractValue(c, other.getValue(c));
          }
      }
docs: Subtracts a factor elementwise from this one.
  @param other The subtrahend.
  @throws IllegalArgumentException If the two tensors have different sizes.