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"Death's End (by Liu Cixin) and the Swordholder problem by Murat

This is the last book in Liu Cixin's Remembrance of Earth's Past trilogy. I had written reviews for the Three Body Problem and Dark Forest before. So for completeness sake, I write my impressions about this book as well. This time I try not to talk much about the plot, and try to keep this spoiler-free.

This book is epic, in terms of the space distance and timeline it covers. It is awe-inspiring in that vastness in space and time sense, and makes you think at the universal scale. This book feels much more hardcore sci-fi than the previous two books, and less believable than them. The book also feels rushed in character/plot development (definitely not length) compared to the previous two books. But all in all, it is a very captivating science fiction and I couldn't stop thinking about it even one week after finishing the book.

The book still has a very cynical and very pessimistic view of human nature (as well as alien nature). The universe is a dark forest, where everyone tries to finish off each other. Everything is bleak, life is meaningless, pointless, and worthless.

On the other hand, the book made me very optimistic about the potential advances in science. The description of four dimensional space is very rich in visualizations. The brainstorming the book induces on what things are possible if you can manipulate the three dimensional space from four dimensional space is inspirational. The potential behind the curvature drive technology (manipulating/changing physical laws) is also amazing to dream about.

One of my main annoyances with the book is the weak character development and naivete in gender dynamics in the book. Cheng Xin, the main character in the story, is portrayed as a weakling. She is very smart (an aerospace engineer) but she is weak and fallible. Like in the original sin, she is blamed for the fall of man, not once but several times. I was aghast at how absurd this portrayal was, and I couldn't stop myself screaming back to the audio-book at several places.

Unfortunately Liu Cixin's women characters have been all one dimensional. Luo Ji's wife was also that way. In the Dark Forest, Luo Ji has created a perfect woman in his imagination: a very submissive, very gentle, soft-spoken, geisha like woman. The worse part is that after that Da Shi had searched China to find the woman that fits the description. It was cringe-worthy to read about how one-dimensional this character was in the book.

Those being said, I want to emphasize again that Cixin Liu is a very talented story teller. (I am very much impressed by the creativity in the stories told from the mouth of Yun Tianming and the technological clues hidden in these stories.) I recommend the series strongly to all science-fiction readers. I also want to recognize the hardwork and talent of the Ken Liu for doing a superb job in translating the books to English. It looks like he has taken a lot of initiative and made creative improvements in the translation rather than doing a straightforward translation.

The swordholder problem
The first part of the book describes the swordholder position, which is sort of a mutual destruction button-holder duty. Initially Luo Ji was tasked as the swordholder. But the problem with the swordholder position is that this puts too much trust in one person. One person becomes responsible for life-death decision of two worlds, the earth and trisolaris.

Liu Cixin has a programming background. He should have realized that this trust problem is better handled by using a Byzantine fault-tolerant consensus protocol. Instead of one person, choose 7 people to act as swordholders and this system will tolerate 2 Byzantine swordholders (because N>3*F).

If we make the assumption that the swordholders don't counsel with each other and each makes a decision on a definite and correct input provided to them, it may be possible to make the system work with N=2F+1 nodes, tolerating more faulty nodes. In that case, just a multisignature solution (with F+1 signatures) could work. (The input is whether the Trisolarans started an attack on Earth. This assumes the input is definite/decisive and binary and it will be visible to the nodes not through other nodes, but through the environment, media, newsreport, and sensors.  And this assumes that for the nonfaulty nodes the input is not faked as in Truman show.)

Yes, this is too many assumptions, so a counsel based solution among nodes, and hence a Byzantine fault-tolerant protocol with N=3F+1, seems to be more appropriate.

Of course, Liu Cixin used the swordholder position for dramatic effect in the novel, but I am a technical person, and I can't get over the fact that the people of three centuries later would be so ignorant of more suitable solutions to the problem.

This brings me back to our time... Is the nuclear button holder position in our time still a single trusted person position? (Related concept: Dead hand) Do we trust a president this much to give him this responsibility? Isn't it time to institute a Byzantine fault-tolerant solution to solve this problem?"