public NodeResources subtract(NodeResources other) {
        ensureSpecified();
        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.minus(other.gpuResources));
    }
Returns this with all numbers set to 0
config-provisioning/src/main/java/com/yahoo/config/provision/NodeResources.java