sql server – Signal wait not the same as wait_time_ms for SOS_SCHEDULER_YIELD

In short, no.

If you read up on SOS_SCHEDULER_YIELD, you’ll see that SOS_SCHEDULER_YIELD is not necessarily indicative of CPU pressure.

Several parts of the description listed on that page are quoted here, to help explain. I suggest reading the rest for more/better context.

This wait type is when a thread was able to execute for its full thread quantum (4 milliseconds in all versions of SQL Server, unchangeable), and so voluntarily yielded the scheduler, moving to the bottom of the Runnable Queue in its scheduler.

The most common cause of SOS_SCHEDULER_YIELD waits that I see is queries doing scans of pages that are in memory and aren’t changing, hence there’s no contention for page access and the scanning thread can run until it exhausts its thread quantum.

One more thing to consider is whether your workload is running on a VM that’s experiencing delays because of the host being oversubscribed. This can elevate the number of SOS_SCHEDULER_YIELD waits

Difference between signal wait and SOS_SCHEDULER_YIELD

I don’t understand the difference between the signal waits column and SOS_SCHEDULER_YIELD wait type when using sys.dm_os_wait_stats.

Is there a good analogy between spectral representation of a signal and graph theory?

I am working on some time series problems where the Fourier representation of the signal in the frequency domain is also important. I am wondering if there is any connection between time series signals consisting of sinusoidal/inherently periodic functions (functions that can be cleanly represented by a sum of sinusoids) and graph theory.

Thanks,
Josiah

How can I plot the Fourier transform of the signal in Matlab?

I have a signal to compute its Fourier transform. I computed the Fourier transform of it as below, but I need to plot its Fourier transform on Matlab. How can I do this?

The signal is:

$$x(t) = e^{-3|t|}sin(2𝑡)u(t)$$

Also, how can I plot the Fourier transform of this signal?

The Fourier transform that I computed is:

$$3j/(9(w+2)^{2})-3j/(9+(w-2)^{2})$$

What should the beep signal signify in fob design?

Fobs typically emit an audible sound, usually a beep, to indicate they have read the key which was swiped. The fob then unlocks if the key swiped was the correct key. Therefore, logically speaking, the beep signal of a fob should indicate that the key has been read by the fob. However, I have found consistently across many fobs that if you swipe the correct key “too fast” the fob will emit the receive key signal, but will not unlock the door.

My question is, what should the beep signal signify to the user? I feel that the beep signal should always, and only, signify reception of the correct key. I see no reason for fobs to beep either for an incorrect key or for an inconclusive swipe. In fact, the crux of my question could be phrased thus: “Should an inconclusive swipe, and a conclusive swipe of the correct key both be signified by the same beep?” I have observed countless times when users hear the beep of a correct key swipe then proceed to open the door only to find it locked and have to swipe again.

end to end encryption – E2EE verification without meeting in person (in Signal)

I’m playing around with e2ee a little. Would it be possible to verify the security numbers in the signal protocol by using already verified e2ee channels within the app securely?

Let E be a commutative cipher and for a message m donate m_ab as m is encrypted with E in a way that only a and b can decrypt it.
Let a: m -> b denote, that a sends message m to b.

I have four parties A,B,C and S, where S represents the application server.

I have verified E2EE encryption for A&B and for B&C, i want to create it for A&C.

Would the following be secure enough to be used in an application (like Signal)?

  1. A&C do a Handshake, but someone could be in the middle (mainly the Server S)

  2. A encrypts (a digest of the) sn for C using an authenticated encryption algorithm and the derived key from 1, calling this hsnA

  3. A sends hsnA to C via B, this is done as follows:

3.1 A: hsnA_ab -> S

3.2 S: hsnA_ab_ss -> B

3.3 B: hsnA_ss_bc -> S

3.4 S: hsnA_bc -> C

3.5 C decrypts it with the keys he has and compares it to his own digest. If the secrets of A and C match then C can also see that the authTag is valid.

  1. C sends a digest of the sn to A in a similar way.

For me this looks like it is sound and correct:

Correctness: If both of them have the same secret this should be secure anyway as hsnA and hsnC are encrypted and only the two of them know how to decrypt it. Neither B nor S can see the message unencrypted at any point in this case.

Soundness:

  1. This obviously allows the server to perform a known-plaintext-attack, but this shouldn’t be an issue for modern ciphers if I recall correctly.

  2. To me it seems like neither B nor S can change the message that is being sent. They could do so if S=B were the man in the middle, but the clients could choose who they trust to be in the middle on each verification

Is there anything I miss? Why is something like this not already implemented for an easier verification process?

notifications – Notify when getting “no signal” on the LG Q6

For several days now, the LG Q6 has made me angry when it suddenly stops detecting the SIM card. (once or twice a day)

I don’t want to discuss the cause and possible solution. (Restart always helps)

The worst part is that the outage cannot be predicted.

Therefore, I want to ask if there is any way that would alert me to this. Either in the absence of a SIM card or on the loss of connection (of course, when the airplane mode is not activated).

exploit – Does my using of a chinese led kit for monitors helps people to intercept electromagnetic radiation from my monitor signal?

My system is compromised, should I look for rootkit or for other ways?
I have an instant leak of data even when my system internet cable is plugged off.
Monitor is the main suspect (2007 with chinese LED kit), videocard(don’t think so) is second,
Keyboard is the other.
How expensive would it be to intercept it? Data leaks to another floor, 3 meters to their equipment, near 1 meter are metal heater radiators of central heating which conduct signal.

If it is a rootkit, how can I check for it if free options doesn’t show anything?
Can it be some kind of RDP?

signal processing – Convolution of function composition of $2t$

I am having trouble calculating a convolution of functions composition.

Given $x(t)$ and $h(t)$, compute the convolution of $2x(2t) star h(2t) $

I tried the following, but I’m not sure if it’s correct:

Set $g(t) = 2x$, $s = 2t$. So now we need to calculate $g(s) star h(s)$:

$displaystyle { g(s) star h(s) = int_{-infty}^{+infty}g(tau)h(s-tau)dtau = int_{-infty}^{+infty}g(tau)h(2t-tau)dtau }$

Please advise. Any help will be appreciated.

terminology – What exactly are “semaphore signal operations” in the Vulkan specification and how do they relate to a CommandBuffer?

In section 7.4.1.Semaphore Signaling of vulkan specification,

https://www.khronos.org/registry/vulkan/specs/1.1-extensions/html/vkspec.html#synchronization-semaphores

“When a batch is submitted to a queue via a queue submission, and it includes semaphores to be signaled, it defines a memory dependency on the batch, and defines semaphore signal operations which set the semaphores to the signaled state.”

What are operations in this sentence?And what is the difference between pipline stages and operations?Is this semaphore signal operation inserted into queue and wait to be executed like stages which a CommandBuffer consists of?