Linked lists
What’s a linked list? Let V be a set of values and A be a set of “addresses”. Say a map f is a “linked list element” compatible with values V and addresses A if and only if f(value)∈ V and f(next) ∈...
View ArticleTrees in informal methods
What’s a tree? First define a sequence or length n> 0 as a total map s: {1,.. n}→ X. Let Nil be the empty sequence. If s is a sequence of length n, and x is an element, then u = sx is the sequence...
View ArticleScott Aaronson’s handwringing
Scott Aaronson is a distinguished professor of computer science at the University of Texas. I ran into his blog a while back, when someone sent me to his muddled defense of Damore and the Google Memo...
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Judea Pearl’s mysterious claim
Pearl: Of course, but you cannot see this noble aspiration in scientific equations. The language of algebra is symmetric: If x tells us about y, then y tells us about x. I’m talking about...
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Pointer alias analysis in C
Perhaps there is some reason to provide a mechanism for asserting, in a particular patch of code, that the compiler is free to make optimistic assumptions about the kinds of aliasing that can occur. I...
View ArticleTorvalds on aliasing
See also pointer alias in C and Depressing and faintly terrifying days for the C standard. From: LKML From Linus Torvalds <> Date Tue, 5 Jun 2018 10:30:21 -0700 Subject Re: [GIT PULL] Device...
View ArticleVector optimization with C aliasing
One of the common defenses of the abuse of “undefined behavior” by C compilers, and the stupid aliasing rules in the standard is that those things are necessary for optimizations, like using vector...
View ArticleThree modest proposals for the C standard WG14
1. Proposal on Undefined Behavior. Rationale: This Standard definition of “undefined behavior”, like the rest of the Standard, relies on an implicit expectation that implementations are cooperating...
View ArticlePractical uses of synchronized clocks -Liskov
From 1991, Barbara Liskov looked at the implications for distributed computing when synchronized clocks are available. Download (PDF, 952KB)
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Flat address spaces: another crank idea for computer architecture
Recently, I have been arguing with people (yes, I know) about the ridiculous “optimizations” compiler developers have invented for the C programming language and one of the most irritating features of...
View ArticleComrades Cheyne and Stokes and mathematics
There is a great book of stories by Soviet era radio astronomer Iosef Shklovsky called 5 Billion Vodka Bottles to the Moon which has a this story (which I tell from memory, no guarantees) In 1953 a...
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Spanner in the works
The developers of Google’s Spanner database built an interesting system but chose to build their own clock synchronization technology instead of getting a more precise off the shelf solution and chose...
View ArticleThe C Standard and GCC/Clang are an active safety and security danger
Code controlling a device – a medical instrument, a power plant, an airplane, perfectly working and thoroughly tested code can be turned into garbage if someone runs a new version of a C compiler or...
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undefined behavior and the purpose of C
The C programming language, by design, permits programmers to work at both low and high level. In particular, for applications like operating system development, cryptography, numerical methods, and...
View ArticleVon Neumann’s critique of automata theory and logic in computer science
from “THE GENERAL AND LOGICAL THEORY OF AUTOMATA” 1947. There exists today a very elaborate system of formal logic, and, specifically, of logic as applied to mathematics. This is a discipline with...
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Semiotics of functional programming
In contrast to the usual imperative languages (e.g., C, Fortran, and Ada), in which variables represent cells in memory that can be modified using the assignment operator = (or :=), functional...
View ArticleJordan Peterson
“Without Christianity, and its emphasis on truth at all costs, science would never have come about.” Questions For 3 Looneys: Was Aristotle Christian? For a nickel: What culture came up with “arabic...
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