keeping simple

Author: yodaiken

  • Processor architecture

    I wish that processor architecture was not so committed to a obsolete model of software. For example, it has become clear over the last few years that the sloppy shared memory thread model of programming has multiple drawbacks. Sharing of data, in particular, should be tightly controlled. Yet processor architectures are “optimized” for unstructured sharing…

  • memories

    For some reason, all copies of an early variant of RTLinux called “myrtlinux” by its Italian “author” have disappeared from the web, but thanks to some archives we can find some fragments from old days.  For example, within a year or two of this email, the story had changed rather  dramatically. To me, there were…

  • Virtualization and power use and spreadsheet games (updated)

    Here’s a thought experiment. Suppose each server uses X watts idle and X+Y watts busy. If you have N programs that currently run on N servers that are Z% idle then in the best case you really only need D= (100-Z)/100*N servers. So in a perfect world you have D machines busy all the time…

  • Microsoft by the numbers

    From correspondent AY: 150,000,000 Number of Windows 7 licenses sold, making Windows 7 by far the fastest growing operating system in history. <10 Percentage of US netbooks running Windows in 2008. 96 Percentage of US netbooks running Windows in 2009. 9,000,000 Number of customer downloads of the Office 2010 beta prior to launch, the largest…

  • Doing it wrong: Poul-Henning Kamp

    Kamp writes to explain that virtual memory behavior can be important for program performance. That is, he explains From the programmer’s standpoint, the working set of information is the smallest collection of information that must be present in main memory to assure efficient execution of his program. But that note is actually from Peter Denning’s…

  • Process algebra reconsidered

    Paper is here. The following incorrect claim is not unusual in the process algebra literature. Basically, what is missing [in classical automata theory] is the notion of interaction: during the execution from initial state to fi nal state, a system may interact with another system. This is needed in order to describe parallel or distributed systems,…

  • R.L. Moore topologist and racist

    If you read this down to the bottom you get a little hint, but you have to read something like this to understand what that little hint means. In graduate school she was very much alone, though she was a grader for an undergraduate course taken by Raymond Johnson. In her first class, she was…

  • out of the loop in silicon valley

    NYTimes. But when she was raising money for Crimson Hexagon, a start-up company she co-founded in 2007, she recalls one venture capitalist telling her that it didn’t matter that she didn’t have business cards, because all they would say was “Mom.” Another potential backer, reports Claire Cain Miller in The New York Times, invited her…

  • More state diagrams

  • limits of state diagrams

    Here’s a graph of a simple state machine of somewhat under 512 states that models  a dumb fifo queue. The initial state is “e” for empty. We can append 1,2 or 3 to this queue and can delete the first in. To simplify suppose the alphabet is {0,1,2,3} where 0 means “dequeue”  and the others…