asciilifeform: these 2 cases overflow, but the fact does not trivially flow from mircea_popescu's equation, you do not know that they will do so by counting the leading 0s

asciilifeform: ( parens have leading zeros count, for convenience )

asciilifeform: 0011 ( 2 ) * 0111 ( 1 ) = 00010101 = 0001 : 0101 ( 3 )

asciilifeform: 0011 ( 2 ) * 0110 ( 1 ) = 00010010 = 0001 : 0010 ( 3 )

asciilifeform: take, e.g., these 4-bit cases:

asciilifeform: however this takes us only in 1 direction.

asciilifeform: 'If l1 + l2 > N-1, the product of a and b can never overflow N.' is true. 'If l1 + l2 < N - 1, the product of a and b will always overflow N.' is also true.

asciilifeform: or hm

asciilifeform: mircea_popescu: 'l1 + l2 < N - 1, the product of a and b will always overflow N.' << didja mean > rather than < ?

asciilifeform bbl.

asciilifeform: ( http://wotpaste.cascadianhacker.com/pastes/RjlFl/?raw=true << same, for 4. in case handy. )

asciilifeform: http://wotpaste.cascadianhacker.com/pastes/T5NY9/?raw=true << same, for 2bit.

asciilifeform: http://wotpaste.cascadianhacker.com/pastes/4jCKm/?raw=true << a mult table, for convenience .

asciilifeform: takes, say, 2 3bit nums, and tells if mul will overflow.

asciilifeform: mircea_popescu: wouldja spare a few min and plox write down algo ?

asciilifeform: rather than 'iff'

asciilifeform: this test only works in one direction

asciilifeform: 111 * 001 = 111 ( 0, 2, 0 leading 0s ) no overflow...

asciilifeform: to do on every mul.

asciilifeform: this is still pretty expensive op tho.

asciilifeform: hmm i see where mircea_popescu is going

asciilifeform: the leading zeros of x1, x2, and result, are 0, 1, 1 respectively.

asciilifeform: 101 * 010 = 001010 (we end up with 010 )

asciilifeform: mircea_popescu: let's, for simplicity, take 3bit regs :

asciilifeform: less than N, or less than leadingzeros(N) ?

asciilifeform: can. and l2.

asciilifeform: because again, fixed register.

asciilifeform: nope.

asciilifeform: we instead have fixed one.

asciilifeform: mircea_popescu's statement is true but doesn't help, because we do not have an elastic register to represent the arity of the mult result.

asciilifeform: or we lost the high bits.

asciilifeform: the result is always N bits long, fixed N. what we want to know is whether it actually represents x1*x2.

asciilifeform: i thought it was clear that thread is about fixed-register arithmetics.

asciilifeform: same arity.

asciilifeform: 0 is 0000...000 for our case.

asciilifeform: mircea_popescu: this only works for addition.

asciilifeform: 1xx * 0 = 0 .

asciilifeform: nope.

asciilifeform: the leading N bits will not be same as product of leading whichevers. because carry.

asciilifeform: i'm thick, explain which op would demonstrate the overflow here.

asciilifeform: there's no 7 in 8245...

asciilifeform: mircea_popescu: expand

asciilifeform: somewhat surprisingly , nothing else works.

asciilifeform: seems like the only guaranteed solutions are either to trial-divide every time (eat 2x the space and 2x the time!) or to keep around 'behind the scenes' 2x the nominal register, so as to have where to overflow into, and then test it for zero (2x the space, and 2x the time ! just like the other 'solution')

asciilifeform: ^ if anyone thinks otherwise, please write in!

asciilifeform: !~later tell phf if you are still working on the puzzle : it is my current understanding that no clean detection of multiply-overflow (when operands and result are all N-bit registers of same N-arity) is possible...

asciilifeform: that'd be something.

asciilifeform: http://12000.org/my_notes/ada/index.htm << linked via subj's www. potentially handy.

asciilifeform: looks vaguely familiar

asciilifeform: whossat

asciilifeform: it's the same story as email hosters etc

asciilifeform: ( the phree hosting is for public material strictly )

asciilifeform: paid hosting thing

asciilifeform: mircea_popescu: it's how they always worked

asciilifeform: 'stotting'

asciilifeform: not even certain that this is a 'morality' tale re dope -- there are 'genius' who behave this way even sans dope.

asciilifeform: ( not everybody is lucky, like adlai et al, and merely gets put in asylum )

asciilifeform: iirc d00d did something or other while on dope, that was later spun as 'threat to public official'

asciilifeform: the genre isn't exactly fresh, or inexhaustible, either.

asciilifeform: afaik fella did not go on to write the next 'gulag archipelag', no.

asciilifeform: noshit.jpg

asciilifeform: was condemned for ... posting a link.

asciilifeform: '“The prosecutor said one thing that was accurate—that I don’t have respect for the laws in this country,” he told TIME. “We have a situation in which the only way we can survive as a free nation is if our laws are not enforced.”'

asciilifeform: https://archive.is/Q7wOv << see also re brown

asciilifeform: ah him -- yes

asciilifeform: afaik was sent nowhere.

asciilifeform: always.

asciilifeform: in retrospect ~everybody 'was asking for it'

asciilifeform: see also buharin et al's 'confession' .

asciilifeform: in the reich with seekrit laws (yes), who is surprised by 'secret plea deal' conditions.

asciilifeform: according, apparently, to the inquisitor in charge of subj.

asciilifeform: schmuck did, after being promised 100 yr (yes) sentence, sign 'plea deal'

asciilifeform: ^ d00d who was nailed as scapegoat for the public rape of stratfor corp

asciilifeform: 'Barrett Brown was re-arrested and taken into custody by Bureau of Prison officials today for speaking to the media.'

asciilifeform: meanwhile in monkeystan, https://archive.is/f41QJ

asciilifeform: and can make 'redskins' out of whoever.

asciilifeform: not only stopped, but turns out it has reverse gear

asciilifeform: aha. who the hell knows what a grown-up german empire could've been like.

asciilifeform: germans weren't so much interested in doing the congo thing, tho, initially more into roman-style 'citizen farmer' land parcelling

asciilifeform: britain still nominally owned, e.g., india, then.

asciilifeform: however peace treaties between megaempires are a lul.

asciilifeform: tru

asciilifeform: didn't work so well for stalin

asciilifeform: aha

asciilifeform: the 'airstripping' was naturally with help from germany.

asciilifeform: the warning does 0.

asciilifeform: every civilization gets ample warning of death. nobody cancelled death yet.

asciilifeform: aaha. ye olde star topology, is the goal. all interactions via Great Inca strictly.

asciilifeform: for physical human to employ, at any rate, yes, quite verboten

asciilifeform: 'If I employ a gardener, I have to earn £3 for every £1 he can actually spend, because everything is taxed twice, first as my income, then as his.' << not only still true in today's reich, but today it'd be 10 : 1 . ☟︎

asciilifeform: normally it is too much to hope for, to keep dodo alive. but can at least stuff him.

asciilifeform: sorta why when i turn up a live dodo, i post it here.

asciilifeform: lulzy.

asciilifeform: ' "Poverty" as defined now (for instance, by the Child Poverty Action Group) would have been called "riches" in many earlier ages. In a similar vein, the child sex abuse industry ensures an ever growing problem and ever growing attention by redefining as sexual abuse things (such as being groped in crowds) that most people would regard as a regrettable but not catastrophic part of childhood, so that its statements about real abuse are

asciilifeform: tru

asciilifeform: but '80s also ?

asciilifeform: today same

asciilifeform: ( this is still the first-rsa-chip d00d from earlier thread )

asciilifeform: i thought it was clear from the text..

asciilifeform: brit