MoritzG

EE

MoritzG's Comments

How dangerous is it to test a vaccine without animal trials?

There is a non zero risk of death. There have been cases where some candidates had severe permanent damage and it took a while to figure out why. We are all slightly different.

Even with animal trials there is a risk. I do not think there is an answer to your question.

Growth rate of COVID-19 outbreaks

Oh, I should have mentioned that this is also assuming that there is a constant factor between the total number of infected in the past to the number of currently infectious. Which is true as long as the spread is exponential, but that is the entire assumption anyhow.

Growth rate of COVID-19 outbreaks

In Germany the data is ATM consistent with:

+22% infected per day which is exactly +3 people infected after one week after the infection by every infected. (This is assuming that there no imported cases, 7th root of ((1+3)/1))

Epistemic standards for “Why did it take so long to invent X?”

"only a minority of people use a bicycle for anything other than recreation"

I guess my upbringing and surrounding is special (densely populated area in north Europe), but I know plenty of people who move in no other way (shopping, vacation, commute, everything). Before the gasoline motor scooter became wide spread, and poisoned the air in Asia, people used bikes all the time.

Epistemic standards for “Why did it take so long to invent X?”

Please elaborate on why you think the bicycle "merely offer convenience or entertainment". I understand that people did not understand it's potential and thought of it as a toy for crazy people, but wasn't the same true for the gasoline-automobile? To me the bicycle is of great importance, not just/only for leisure, sport. I understand that the bicycle's value depends on the distance, flatness, wind, road quality traveled, but compared to a horse (that most did not have) it is so much better.

Matrix Multiplication

The entire SIMD vector approach is good for many dot products but it is not the same as a systolic array for rank two on rank two multiplication.

If the job would be to multiply two 1024x1024 matrices then a systolic array of 256x256 MACs would be a good choice. It would work four times on 256x1024 by 1024x256 matrices for 1024+256 steps.

Matrix Multiplication

To me there is a difference between the hardware for 1xN by Nx1 and MxN by NxM (with N > M > 1). Although any matrix operation is many 1xN by Nx1 dot products, doing them independently would be inefficient.
"If you do a matrix multiplication the obvious way, this results in dot products of rows and columns (one for each element of the resulting matrix). So it seems to me that improving matrix to matrix multiplication performance comes from improving the performance of dot products."
True, but not individual dot products, but the collective of very many dot products. Obviously you do not do it the obvious way as you would have to load the same data over and over again.

Matrix Multiplication

An example of a systolic algorithm might be designed for matrix multiplication. One matrix is fed in a row at a time from the top of the array and is passed down the array, the other matrix is fed in a column at a time from the left hand side of the array and passes from left to right. Dummy values are then passed in until each processor has seen one whole row and one whole column. At this point, the result of the multiplication is stored in the array and can now be output a row or a column at a time, flowing down or across the array.
https://en.wikipedia.org/wiki/Systolic_array

How does electricity work literally?

True, I had not claimed that all criteria could or have been met. Because of the noise and the heat I just the other day replaced the inductive load in some of my very old but still fully functioning kitchen counter lights, with modern switching current regulators. The 50 Hz produce a 100 Hz tone that had been bothering me for decades. But even some of those can be heard by some people. (Not me I am deaf to anything >10kHz)

It is a compromise in an area of sensory overlap but the human senses are not equally sensitive to all frequencies. Your hearing is way better at 3kHz. At your age you will still remember CRT monitors that would operate at 60 Hz at max resolution, bad but they did get used.

How does electricity work literally?

Why 50/60Hz? It has to be too low to be heard, to high to be seen, high enough for transformation, low enough for low induction losses, low enough for simple rotating machines. Trains can not use 50/60 so they went with 1/3 (16+2/3 Hz or 20 Hz)
Grid frequency is controlled to +-150mHz if that fails private customers might get disconnected/dropped.
The time derivative of the grid frequency is a measure of the relative power mismatch.

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