Archive for July 30, 2020

Thursday, July 30, 2020

Speculation in JavaScriptCore

Filip Pizlo:

This post is all about speculative compilation, or just speculation for short, in the context of the JavaScriptCore virtual machine. Speculative compilation is ideal for making dynamic languages, or any language with enough dynamic features, run faster. In this post, we will look at speculation for JavaScript. Historically, this technique or closely related variants has been applied successfully to Smalltalk, Self, Java, .NET, Python, and Ruby, among others. Starting in the 90’s, intense benchmark-driven competition between many Java implementations helped to create an understanding of how to build speculative compilers for languages with small amounts of dynamism. Despite being a lot more dynamic than Java, the JavaScript performance war that started in the naughts has generally favored increasingly aggressive applications of the same speculative compilation tricks that worked great for Java. It seems like speculation can be applied to any language implementation that uses runtime checks that are hard to reason about statically.



Felix Rieseberg:

This is Mac OS 8, running in an Electron app pretending to be a 1991 Macintosh Quadra. Yes, it's the full thing.

Via Dan Moren:

I fired it up to take it for a spin and it worked pretty well, though I did run into some bugs with scrolling (the scroll box doesn’t really move, though you can scroll down). It’s been pre-loaded with some games and demos, which Rieseberg apparently sourced from a Macworld Demo CD.

It’s even got Netscape, although the Internet connection doesn’t work.


Keeping Dropbox

David Sparks:

iCloud Drive and sharing have not failed me. On the contrary, they have worked better than I expected.


The trouble is those instances where I am not in control. For example, I have many clients who have never heard of iCloud Drive and do not own Macs. They have, however, all heard of and installed Dropbox. When you work in a service industry, adopting a technology that requires your clients to change their technology never works.


I did not install the Dropbox app on my laptop but instead use their web interface when I need to access my Dropbox storage. It cuts me out of a lot of automation, and it is generally slower, but I can avoid its intrusive install this way.

Bradley Chambers:

I love iCloud Drive, and I’ve been using it as my primary file storage method for a couple of years at this point. […] The only thing I am not using is the legacy shared folders I have in Dropbox. My biggest complaint about iCloud Drive is that the deleted file restoration pales in comparison to Dropbox.


Exposure Notification Update

Howard Oakley (Hacker News):

According to figures obtained by the BBC, of the 83 million people in Germany, only around 16 million have downloaded this app since it launched in June. That’s less than 20% of the whole population, and probably around a quarter of all smartphone users. Its adoption has been far below the percentages envisaged by those modelling the benefits of such apps, which normally start to become significant once adoption exceeds 50% and rises towards 80%.

Because the German app has respected data privacy, Public Health authorities have gained almost no information about Covid-19 outbreaks from the app. They know that about 500 users of the app have tested positive – that’s an insignificant proportion – and no one can find out how many contacts have been successfully traced as a result. There is also no record of how many exposures resulted in false alarms, nor of missed diagnoses. There are similar problems with Switzerland’s app, and a lack of data for Ireland’s too.

Adoption of smartphone contact tracing apps has also been very poor in Japan (6% of the population), Italy (7%), and France (3%). To date, no national smartphone contact tracing app has been demonstrated to have had any significant benefit in controlling outbreaks, or significantly reducing the incidence of Covid-19. Only draconian access to personal data, as used in South Korea, seems to have brought any positive results.

Joe Wituschek:

Despite its quick turnaround in creating the technology, barely any states in the United States are planning on adopting Apple and Google’s Exposure Notification technology.


Oklahoma, Alabama, South Carolina and Virginia are the only states signed on to build their apps with the technology.


Almost a quarter of states currently have no plans to build a digital solution to help assist in the effort.

See also: Nick Heer.


Update (2021-03-14): John Gruber:

The whole endeavor seems pointless, looking at these numbers. If anything, it might be giving the users of these apps a false sense of security. If you use one of these apps and are exposed to someone who later tests positive, the odds that that person both uses the app and will report their positive test result seem not just low but downright infinitesimal.

Update (2021-03-22): Howard Oakley:

Feasibility modelling used to decide whether to proceed to develop the app in the first place had been based on the assumption that about 60% of the population would use it; in reality that percentage hasn’t even reached half that (28%). Detailed analysis has also revealed that app uptake has been lowest in areas with densest population, such as London, where cases have also been most frequent during the second wave.

Research on the effectiveness of that and other Exposure Notification apps has been scant and of shockingly poor quality. A recent brief review has clutched at the straws offered in just six studies, most of which have had to rely on modelling to predict what might be expected, rather than measuring what has been achieved. To realise any significant public health benefits from smartphone apps, they desperataly need many more users, and deeper links to healthcare and sensitive personal information. The Apple-Google dream of Exposure Notification in a privacy vacuum simply doesn’t do enough to have an impact on the pandemic.