public NodeResources add(NodeResources other) {
        ensureSpecified();
        if ( ! this.isInterchangeableWith(other))
            throw new IllegalArgumentException(this + " and " + other + " are not interchangeable");
        return new NodeResources(vcpu + other.vcpu,
                                 memoryGiB + other.memoryGiB,
                                 diskGb + other.diskGb,
                                 bandwidthGbps + other.bandwidthGbps,
                                 this.diskSpeed.combineWith(other.diskSpeed),
                                 this.storageType.combineWith(other.storageType),
                                 this.architecture.combineWith(other.architecture),
                                 this.gpuResources.plus(other.gpuResources));
    }
Returns this with all numbers set to 0
config-provisioning/src/main/java/com/yahoo/config/provision/NodeResources.java