49 Matching Annotations
  1. Mar 2023
    1. Power Vessels

      All around white mast light

    2. Large Power Ships over 50 m

      Forward facing mast light. Two if > 50m.

    3. Pilot Boats

      White over Red.

      Flag: Red, white

    4. Towing

      Two forward white. Yellow aft

      Flag: rhombus

    5. Restricted in Ability to Maneuver

      Red White Red. Flag: Rhombus between two circles

    6. Constrained by Draft

      Three red. Black cylinder flag

    7. Fishing with nets etc - trawling

      Green over white. Sandclock flag

    8. Fishing with a long line

      Red over white.

      Flag: sandclock

    9. Dredging or cable laying - underwater operations

      Red White Red, RR on danger side, GG on the non-danger side.

    1. Backing and Veering Winds

      Passage of a cold front shifts the wind direction to be more clockwise direction -- veering wind in the NH.

      SH: a more anticlockwise direction -- a backing wind.

    2. the cold air strikes the warm, the warm air is immediately and violently lifted. As the warm air rises, water vapor is released. Thus, at the front line you will see massive clouds and rain and a sudden change in temperature.

      The change is not gradual essentially

    3. unequal heating of masses of air

      sets up a thermal gradiet

    1. Current

      Movement of water

      Local currents: tidal ones which switch direction.

    2. depths listed on charts are marked with the low tide depth

      minimum depth.

    3. Tides are the regular rise and fall of the ocean

      Dynamic depth of the water.

    4. depth of the keel will be around 4 to 7 feet

      ~1/7, the length of the boat here.

    5. continue because there is nothing to stop them

      Waves are just transfer of momentum. And they continue if there's nothing to sap its momentum -- ex wind or subsurface structure.

      Maybe the origination was distant storms or tsunami etc.

    6. waves get steeper and steeper their tops become tenably unstable.

      Interaction of waves with wind (besides construction)

    7. waves are primarily the result of surface wind action,

      wave power is a function of amplitude

    1. Fairlead Control

      This is relatively straightforward but took me quite a lot of time to get.

      There are two points of interest: 1. top of the sail -- influenced by the leech and the slack therein. 2. bottom of the sail -- influenced by the slack in the foot.

      Structure created by slack in (1): a twist/pouch at the top. This pouch exposes the exterior region to higher wind and shields the interior region from wind.

      Structure created by slack in (2): the bulging of the sail. And again you might or might not want this on the interior or the exterior sides.

    2. in wind you'd expect that the foot might pooch out more

      fairlead forward \(\implies\) fills out the inner sail.

      Help with the inner flutter of the tales. Should help the outer flutter as well -- but towards the bottom, not the top.

    3. move the fairlead all the way forwar

      This means, increased tension all the way on the leech -- limiting its freedom with wind. Not letting it twist on the top -- where the wind is high -- quite as much for instance. This also means the wind at the top would behave similarly to the rest of the sail.

      The foot has decreased tension which means it can inflate to port (if on-starboard), or starboard (if on-port).

    4. Reach

      Mid level slack on the jibsheet.

      Mid-left fairlead leds to top two port tales fulltering. Not enough wind on the inside top. Loosening the leech would do it. (no, it's the opposite.)

      Loosening the foot allows the sail to fully inflate leading to the port geting more wind.

    5. When the sail twists out, more wind flows on the outer side of the sail and will thus straighten out the crazy red telltale.

      Notable bit: how this helps the port side.

      This allows the sail to twist out more upwards, which given the wind is from starboard allows more wind to flow on the outer side.

    6. bottom ones are flying fine but the top red is flying wildly.

      Implies: not enough wind on the port side up top.

      If the foot has low tension, then the bottom would inflate out, but the top wouldn't be.

      So increase foot tension (pull back) and give the leech some slack.

    7. move the fairlead all the way back towards the cockpit

      "Putting more tension on the foot, easing out the leech."

      "leech would twist out and away downwind". Especially at the top.

    1. Trim

      Trim: length of sheet to the sail.

      Over trim: pulled in too much Under trim: given too much slack

  2. Aug 2022
    1. IBPB command event, or (on processors which support enhanced IBRS) either a VM exit with IBRS set to 1 or setting IBRS to 1 after a VM exit.

      So either a barrier via IBPB or IBRS=any?

      after case: the IBRS, presumably walks and cleans up context specific state? already set: checks for it on control change?

    2. IA32_SPEC_CTRL.IBRS is set either at or after a VM exit.

      What if the guest resets it? Where do we handle that?

  3. Oct 2017
    1. he thing is, it’s really nice here, except when it isn’t. Those Seminole War soldiers would be stunned to see how this worthless hellscape of swarming mosquitoes and sodden marshes has become a high-priced dreamscape of swimming pools and merengue and plastic surgery and Mar-a-Lago. It probably isn’t sustainable. But until it gets wiped out—and maybe even after—there’s still going to be a market for paradise. Most of us came here to escape reality, not to deal with it.

      Nightfall -- night every 5000 (or whatever years) lead to the fall of civilizations. Helliconian winter did the same thing (I think).

      The amazing thing is that there the event was actually unexpected.

      In Florida and similar places, we repeat these mistakes, inspite of knowing that they are mistakes, because we've built structures [0] that almost compel them.

      Those structures were built because other structures -- political, capitalistic, whatever.

  4. Sep 2016
    1. all possible chains of composable graph edges

      How would you create peano numbers like this?

    1. pure functions

      Or alternately functions in their math sense (morphisms).

    2. operational semantics

      Just like operational definition

    3. A mathematical function does not execute any code — it just knows the answer. A Haskell function has to calculate the answer.
    4. you can’t have a set of all sets
    5. polymorphic functions that involve circular definitions

      Polymorphic functions, like foldr, id, map are functions which can act on a multiple types of sets.

      Higher level functions are arrows in categories whose objects are other categories.

      The circularity here comes in because higher order functions reference themselves -- via reduction sequences.

    6. types is that they are sets of values

      Going back to cat-theory for a bit, we had objects and we had arrows.

      Arrows are morphisms -- structure preserving map between objects. Now, we are talking about categorization of objects into separate sets.

    7. It’s a common practice in Haskell to start a project by designing the types. Later, type annotations drive the implementation and become compiler-enforced comments.

      Design the types, the structure, essentially the surface of the program.

      Then fill in the implementation, the volume and let the compiler take care of validating the implementation.

    8. Types Are About Composability

      Types enforce structure, which enables composability.

    1. morphisms,

      From wikipedia:

      morphism: *structure preserving map from one mathematical structure to another

      structure is an aggregate thing -- about the domain not about any one object in the domain.

      In set theory, morphisms are functions; in linear algebra, linear transformations; in group theory, group homomorphisms; in topology, continuous functions

      So, in set-theory functions are structure preserving maps from a set to another.

      In linear algebra, linear transformations are structure preserving maps from ...

      In group theory, group homomorphisms are structure preserving maps from elements of the group (?) to ...

      In Topology, continuous functions are structure preserving maps from one /region/ (?) to another.

      In category theory, morphism is a broadly similar idea, but somewhat more abstract: the mathematical objects involved need not be sets, and the relationship between them may be something more general than a map.

    2. ategory consists of objects and arrows that go between them

      Based on the arrow being a morphism/function (see below), it seems that the domain and the co-domain should be able to be disjoint.

      Also, here A->B and A->C; the dual map means that an arrow is not a function.

    3. essence of a category is composition. Or, if you prefer, the essence of composition is a category

      Alternately stated: All you can do with categories is composition?

  5. Aug 2016
    1. are given a transistor allocation

      which changes with process. But, perhaps slower now.

      But it does illustrate how much you design to a process.

    2. Opterons

      Opteron was 2003. Nehalem, 2009.

      That's a long gap. But of course they messed up with Barcelona.

    1. You have another function g that takes a B and returns a C. You can compose them by passing the result of f to g. You have just defined a new function that takes an A and returns a C.

      That clears that. Arrow A->B and arrow B->C are not necessarily the same arrow (function).

      Okay, so what are we doing here? Category is a set (?) of objects with arbitrary functions between them. The only property that this needs to satisfy is one of transitivity.

    1. locks don’t compose,

      They don't commute sure, but what if we are really careful with them and make sure there are no cycles.

      Of course you could have locks where they protect overlapping regions -- that seems problematic.

    2. Functional programming is not only about composing functions and algebraic data structures — it makes concurrency composable

      This seems to refer to my last comment: composition is not just about composing function and ADTs, but also makes concurrency composable.

      From this first lvar paper: http://lambda-the-ultimate.org/node/4823, if two sets of modifications can be structured to commute, then they are guaranteed to be thread safe and thus can be composed.

  6. Jul 2016
    1. When you set your official releases to build with -Wall -Werror or the equivalent, you're putting yourself on quicksand. It's basically guaranteed that future compiler versions will have different opinions on what to warn about, which means that official releases of your software are going to stop building at some point in the future for no good reason. Having your software stop building for no good reason is not helping people.

      TL;DR version.

    1. hile Oracle is building its own public cloud, it does not have the kind of scale that these companies do, but it does have something else that warrants customization and co-design up and down its stack: more than 420,000 customers who generate $38.5 billion in sales.

      Why would Oracle build custom hardware?

      Oracle does have few large customers. Note that the public cloud efforts of MSFT, GOOG, AMZN are trying the same thing -- just with different set of technologies.