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+ - SageMathCloud's new Storage Architecture->

Submitted by phatsphere
phatsphere (642799) writes "William Stein summarizes his experience of creating a highly scalable, continuously backuped and replicated storage infrastructure for SMC, based on ZFS, bup, rsync & co:

Consistency and availability are competing requirements. It is trivial to keep the files in a SageMathCloud project consistent if we store it in exactly one place; however, when the machine that project is on goes down for any reason, the project stops working, [...]. By making many copies of the files in a project, it's fairly easy to ensure that the project is always available, even if network switches in multiple data centers completely fail, etc. Unfortunately, if there are too many users and the synchronization itself puts too heavy of a load on the overall system, then machines will fail more frequently, and though projects are available, files do not stay consistent and data is lost to the user.

and boldly summarizes

The architecture that we have built could scale up to a million users.

"

Link to Original Source

Comment: Similar Projects (Score 1) 113

by William Stein (#37238614) Attached to: Python Fiddle, an IDE That Runs In Your Browser

Both the Sage notebook and codenode are similar projects that support development of Python programs via a web browser interface. They have been around for about 4 years, and full source code is available for both in case you want to setup your own server (there are dozens of Sage notebook servers used at universities around the world).

Comment: Re:College Textbook Prices (Score 1) 260

by William Stein (#33282732) Attached to: Sell Someone Else's Book On Lulu!

I am a mathematics professor at the University of Washington in Seattle, and I published a textbook that I use in a course I teach. According to Washington State law, any royalties I receive as a result of purchases of my textbook by students in the course must be donated to the university (I tracked student purchases and donated a corresponding amount to UW). Second, I got permission from the publisher (Springer-Verlag) to make a free PDF version of the book available.

Image

4G iPhone Misplacer Invited To Germany For Beer 164

Posted by samzenpus
from the beer-makes-things-better dept.
eldavojohn writes "You may recall the hapless engineer who left a fairly sensitive iPhone at a bar recently. Well, in a PR stunt, Lufthansa has invited him to visit Germany on their dime after citing his latest Facebook status, 'I underestimated how good German beer is' as well as his obvious passion for German beer and culture. It's not clear if Gray Powell has decided to 'pick up where he last left off' (as the letter puts it). I know what my decision would be."

Comment: Re:Poor QA (Score 1) 626

by William Stein (#29936989) Attached to: Why Computers Suck At Math

(1/10)^n for integer n is irrational in base 2 and the truncation was unavoidable.

Whether or not a number is irrational does not depend on the base. The number (1/10)^n is rational in any base. By irrational, maybe you meant "finite decimal expansion"?

Unrelated: The article starts with the example 599999999999999 - 599999999999998 = 0 in Google. Fortunately some software gives the correct result by default.

Comment: Re:For anybody who's curious... (Score 3, Insightful) 94

by William Stein (#29508843) Attached to: Finding the First Trillion Congruent Numbers

That's a good explanation. I have to emphasize though, that they actually found all the congruent numbers up to a trillion only under the completely unproven hypothesis that the Birch and Swinnerton-Dyer conjecture is true. It's entirely possible that this conjecture is false, and some of the numbers they found are actually not congruent numbers. However, part of the conjecture is known (by work of Coates and Wiles -- the same Wiles who proved Fermat's Last Theorem), so we do know that all numbers they didn't list are definitely not congruent numbers.

Comment: Re:Hard Drive? (Score 2, Interesting) 94

by William Stein (#29508805) Attached to: Finding the First Trillion Congruent Numbers

I own the 128GB RAM, etc., computer that the second group did the computation on. I have a Sun X4550 24TB disk array (ZFS) connected to it, but I only allocated a few terabytes of space for a scratch disk. They were well into the calculation when I found out what they were up to (I was initially annoyed, since they were saturating the network). I think they were just being polite to me and the other users by not using a lot more disk.

Comment: Re:"outlined in detail" != "here's some pseudo cod (Score 1) 94

by William Stein (#29508757) Attached to: Finding the First Trillion Congruent Numbers

I asked them before this came out, and they said they didn't want to post their code on the press release in order to avoid being slashdotted. Seriously. I think the code is certainly available upon request, and will be made available later when the hoopla dies down. Much of it is in FLINT, which is part of Sage.

Comment: Re:Why? (Score 2, Informative) 94

by William Stein (#29508725) Attached to: Finding the First Trillion Congruent Numbers

It is an *open problem* to show that there exists algorithm at all to decide whether a given integer N is a congruent number. Full stop. It's not a question of speed, or even skipping previous integers. We simply don't even know that it is possible to decide whether or not integers are congruent numbers. However, if the Birch and Swinnerton-Dyer conjecture is true (which we don't know), then there is an algorithm.

Software

+ - Open Source Software Brings Transparency to Math->

Submitted by
William Stein
William Stein writes "The free open source mathematics program Sage that was recently mentioned on slashdot just won first prize in the scientific software category of Les Trophees du Libre, an international competition for free software. Soon Sage will face off against the major software companies in San Diego at the American Mathematical Society Meeting."
Link to Original Source

FORTRAN is a good example of a language which is easier to parse using ad hoc techniques. -- D. Gries [What's good about it? Ed.]

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