A Message From Don

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A Message From Don Knuth, 01 September 2011

Welcome to all lovers of clean (or nearly clean) hardware design!

During the 1990s I spent considerable time designing a computer that would be representative of modern machines, yet easy to learn. Several of the leading experts in the field gave me considerable help with the design. The result was MMIX — 'A RISC computer for the new millennium'. In 1999 I completed the preliminary software to support basic MMIX programming and the simulation of many versions of the architecture. During the subsequent twelve years, this software has seen extensive use and it has successfully passed many 'torture tests'. Therefore I decided in September 2011 that it is now in such a satisfactory state that the current version of the software should become 100% stable — never again changing. This means that other software can be built around it, with the assurance that the underlying MMIX engine will remain the same forevermore.

(Realistically, I know that some bugs must still exist. After all, these are the most difficult programs that I've ever written! The pipeline meta-simulator allows an almost infinite variety of complex incarnations of the architecture to be configured; most of the dizzying combinations of multiple-issue, branch prediction, functional units, cache configurations, etc., etc., have therefore never yet been tried extensively. But such bugs exist also in real computers, and we have learned how to work around them.)

I believe MMIX is the best existing computer for educational purposes, if students want to experience a realistic machine with a minimum of kludgey inelegance. But it's also much more, because the meta-simulator allows us to experiment with an essentially unlimited variety of 'virtual' machines that would be prohibitively expensive to build; we can see how much faster such computers would be able to operate, before deciding whether to actually manufacture them. Every time I play with this software, I'm struck by what a superb testbed it provides for system studies — and I wish that I had another lifetime in which I could explore these things personally. Furthermore I can see many other features, not present in MMIX Version 1, that ought to be studied carefully.

However, other people can do such things better than I. My own personal 'calling' is to write about the process of computer programming, and to survey and organize the fascinating algorithms that computer scientists keep inventing at a great rate. Therefore I'm extremely pleased that I can now 'pass the baton' to the excellent group of MMIXmasters at Munich University of Applied Science. For more than a decade, they've been leaders in the pedagogical uses of MMIX, and they've made significant contributions to interfaces between MMIX and other aspects of computing.

One thing that particularly interests me is the conversion of the machine language programs in Volumes 1, 2, and 3 of The Art of Computer Programming from the MIX computer to MMIX. I must finish writing Volumes 4 and 5 before I do this conversion myself. But I welcome attempts from readers who wish to propose what they think are the best MMIX equivalents of the existing MIX code. I probably won't have time to comment on such draft programs for several years, because the task of writing new material is so all-consuming; but I'm sure that well-written MMIX drafts will be enormously helpful to me when I do get around to preparing the next editions of Volumes 1, 2, and 3. So my hope is that people can use this website to share their ideas about such converted code. Paul Erdős often spoke of mathematical proofs that are so good, they belong to 'The Book'; can you write MMIX programs that belong to 'The Book'?

Happy hacking!

Don’t fall for this Facebook private message scam. But instead of sending the same message to friends, the criminals will message contacts with malicious links and suspicious online offers. The officials offered what they called a “prescription” for Californians to slow the virus spread, a marketing effort dubbed “Don’t share your air.” The underlying message is to stay away from people from other households, which is what many failed to do at Thanksgiving.

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California’s health care system is in the throes of a coronavirus crisis stemming from ill-advised Thanksgiving gatherings

California’s new virus message: ‘Don’t share your air’By DON THOMPSONAssociated PressThe Associated PressSACRAMENTO, Calif.

SACRAMENTO, Calif. (AP) — California’s health care system is in the throes of a coronavirus crisis stemming from ill-advised Thanksgiving gatherings, top executives from the state’s largest hospital systems said Tuesday as they put out a “desperate call” for residents to avoid a Christmas repeat they said would overwhelm the state’s medical system.

Increasingly exhausted staff, many pressed into service outside their normal duties, are now attending to virus patients stacked up in hallways and conference rooms, said officials from Kaiser Permanente, Dignity Health and Sutter Health, which together cover 15 million Californians.

The CEO of the Martin Luther King, Jr. Community Hospital in Los Angeles, Dr. Elaine Batchlor, separately said patients there have spilled over into the gift shop and five tents outside the emergency department.

The officials offered what they called a “prescription” for Californians to slow the virus spread, a marketing effort dubbed “Don’t share your air.” The underlying message is to stay away from people from other households, which is what many failed to do at Thanksgiving.

“We simply will not be able to keep up if the COVID surge continues to increase,” Kaiser Permanente chairman and CEO Greg Adams said. “We’re at or near capacity everywhere.”

The state reported 32,659 newly confirmed cases Tuesday and another 653 patients were admitted to hospitals, one of the biggest one-day hospitalization jumps. A state data models predict nearly 106,000 hospitalizations in a month if nothing changes. The current level is 17,843.

The officials blamed Thanksgiving transmissions they fear will be repeated if people gather for Christmas and New Year’s and don’t take precautions like wearing masks, socially distancing, staying home as much as possible and not socializing with others.

“We are really making a clarion and desperate call to Californians to not repeat what happened at Thanksgiving,” said Dr. Stephen Parodi, The Permanente Medical Group’s associate executive director. “Our hospital systems cannot afford to see another increase like we saw with Thanksgiving.”

California Health and Human Services Secretary Dr. Mark Ghaly reiterated that the state’s modeling shows some hospitals and regions of the state will be overwhelmed in coming weeks if the current surge continues. But he said that’s not a given.


“Let’s make some choices over the next 10 days that we will never regret, because our families, our loved ones, our communities will be more intact because of it,” he said. Software gratis.

California imposed a new regional stay-at-home order in early December that is based on ICU capacity and shuttered or restricted capacity levels for a huge swath of businesses. The state’s overall capacity or regular ICU beds had fallen to 1.4% Tuesday and for another day it was at 0% for all of Southern California and the 12-county San Joaquin Valley to the north. Many hospitals are now using emergency “surge capacity.”

“We don’t have space for anybody. We’ve been holding patients for days because we can’t get them transferred, can’t get beds for them,” said Dr. Alexis Lenz, an emergency room physician at El Centro Regional Medical Center in Imperial County, in the southeast corner of the state. The facility has erected a 50-bed tent in its parking lot and was converting three operating rooms to virus care.

Imperial County now is seeing 20% of people tested come back positive, compared with the state average of about 13%.

Officials in hard-hit Fresno County in the San Joaquin Valley meanwhile said temperature trackers on their 14,800 Moderna vaccine doses show that some will need replacing, though the vaccine doesn’t need the same ultra-cold care as the Pfizer vaccine.

Vaccine shipments aren’t used if there are “temperature irregularities” as occurred Monday with a shipment to Fresno, said California Department of Public Health spokeswoman Ali Bay. A replacement shipment should arrive Wednesday, she said.

A Message From Donald J Trump

“Temperature irregularities are rare, but they do occur,” she said in an email. “The federal government, manufacturers, distributors, the state, and local government have all planned for this possible scenario and have a system in place to ensure it is immediately addressed.”

A Message From Don Moen

Dr. Thomas Utecht, chief medical officer for Community Medical Centers in Fresno, related how medical staff daily see sobbing families, desperate patients and people dying in isolation wards with their loved ones watching remotely.

“Every heart wrenching hour we try to save another patient with everything we have. Sometimes it’s enough. And sometimes it’s not,” he wrote in a direct appeal to the state’s residents. “It’s up to you, you are the frontline now,. We can only do so much without your help.”


A Message From Don Felder

Associated Press reporters John Antczak in Los Angeles, Elliot Spagat in San Diego and Janie Har in San Francisco contributed to this report.