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From (1) Fear of Macros ( this is from someone that mainly program in racket, not my personal opinion)

But the moment I stepped past routine pattern-matching, I kind of fell off a cliff into a terminology soup. I marinaded myself in material, hoping it would eventually sink in after enough re-readings. I even found myself using trial and error, rather than having a clear mental model what was going on. Gah.

(1) https://www.greghendershott.com/fear-of-macros/all.html

My personal opinion: I think racket is more an ivory tower for researcher, many for northwest university. “PLT” refers to the group that is the core of the Racket development team. PLT consists of numerous people distributed across several different universities in the USA.

As I am getting older I should prefer some middle ground between racket and go. Hygienic macros are difficult to understand in this context, that is I don't want to buy the power of hygienic macros, it is over sold.

Anyway, I admire Mattew Flatt efforts in compilation tecniques and the author of Beautiful Racket.

Long time ago hygienic macros move me to decide to farewell racket. Common Lisp, clojure or scheme allow me to program in Lisp when I have some code to do. So I don't look back to racket. /rant

Edited: Hygienic macros are powerful but as an user of a computer language and not as a researcher I find them very difficult to grasp compared to Common Lisp macros. And this is only the tip of the iceberg, what is down is that the language is more oriented to researcher than to get things done. Should I work in Northwest University, I would appreciate a lot those complexity and make progress in the field, but that is not my cup of tea now. I don't have problems to program in Haskell or any other language, but I don't buy racket complexity.

Since aging reduces vitamin D production in skin, we have that vitamin D level is correlated with age that is correlated with worse response to COVID-19.

Aging reduces vitamin D production in skin. There is a decrease in the concentration of 7-dehydrocholesterol in the epidermis in old compared with young individuals and a reduced response to UV light, resulting in a 50% decrease in the formation of previtamin D3

I think that low testosterone levels is correlated with being older which is correlated with worse Covid-19 outcomes, so age is the important factor here.

A month or so ago a paper about a deep learning model using a cpu beating the best (4000$ or so) nvidia gpu was on hn, the trick was a quick hashing technique similar to nearest neighbour, so the algorithm keep only the most active neurons. I think the gpu price was about 4000$ and the computer was 60% of that based on some ball park estimates from the comments in HN.

Edited: This is the paper:https://news.ycombinator.com/item?id=22502131

Perhaps both techniques can be used together, since the paper take advantage of sparcity to beat gpu when computation are on a sparse subset.