LATCH | Fastest CPU implementation of the LATCH | GPU library
kandi X-RAY | LATCH Summary
kandi X-RAY | LATCH Summary
Fastest implementation of the fully scale- and rotation-invariant LATCH 512-bit binary feature descriptor as described in the 2015 paper by Levi and Hassner:. "LATCH: Learned Arrangements of Three Patch Codes"
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QUESTION
I'm working to integrate Spring Cloud Streams with Kafka binder. Aim is my app consumes json from the topic and deserialize it to the Java object. I am using the functional style approach instead of imperative. My code is working with well-structured json inputs.
On the other hand, when I send the invalid json, I want the error logging method to be triggered. This works in some test cases and does not work in another. My application deserializes json even if it is invalid and triggers the method which contains logic, not the error logging one.
I could not solve the problem why the framework deserialize some unstructured json input.
...ANSWER
Answered 2021-Jun-04 at 14:59Jackson does not consider that to be invalid JSON, it just ignores the trailing }}
and decodes the {}
as an empty object.
QUESTION
I have data of devices and its latitudes, longitudes all stored as varchar in PostgreSQL. When my device isn't able to latch on to the GPS - the lat, long is stored in the table as '-1.0', '-1.0'. Here is how the table looks like:
I'm trying to calculate on per day basis, the GPS availability percentage. Which is, the ratio the number of times device had GPS (the lat, long was not -1.0, -1.0) to the total number of GPS pings sent throughout the day.
I made some effort on this:
If want to know on daily basis, how many times each device had GPS (lat, long were not -1.0, -1.0). This is the query:
...ANSWER
Answered 2021-Jun-02 at 13:25You can achieve this a few different ways e.g. subquery, cte etc. Here is a cte example:
QUESTION
I currently have a text-area with the following CSS class:
...ANSWER
Answered 2021-May-28 at 22:11Nevermind, I think I've figured out what you're trying to do based on the comments in your edit. You can set the scrollLeft
property programmatically to keep the cursor right-aligned:
QUESTION
I am referencing from Baeldung.com. Unfortunately, the article does not explain why this is not a thread safe code. Article
My goal is to understand how to create a thread safe method with the synchronized keyword.
My actual result is: The count value is 1.
...ANSWER
Answered 2021-May-17 at 21:33Why int temp = count; wait(100); count = temp + 1;
is not thread-safe? One possible flow:
- First thread reads
count
(0), save it intemp
for later, and waits, allowing second thread to run (lock released); - second thread reads
count
(also 0), saved intemp
, and waits, eventually allowing first thread to continue; - first thread increments value from
temp
and saves incount
(1); - but second thread still holds the old value of
count
(0) intemp
- eventually it will run and storetemp+1
(1) intocount
, not incrementing its new value.
very simplified, just considering 2 threads
In short: wait()
releases the lock allowing other (synchronized) method to run.
QUESTION
Please Help me
I was trying to do ALU for 4 bit with selector. I'm getting errors like this:
**WARNING:Xst:737 - Found 1-bit latch for signal <1>>. Latches may be generated from incomplete case or if statements. We do not recommend the use of latches in FPGA/CPLD designs, as they may lead to timing problems.
WARNING:Xst:737 - Found 1-bit latch for signal <0>>. Latches may be generated from incomplete case or if statements. We do not recommend the use of latches in FPGA/CPLD designs, as they may lead to timing problems.
WARNING:Xst:737 - Found 1-bit latch for signal <3>>. Latches may be generated from incomplete case or if statements. We do not recommend the use of latches in FPGA/CPLD designs, as they may lead to timing problems.
WARNING:Xst:737 - Found 1-bit latch for signal <2>>. Latches may be generated from incomplete case or if statements. We do not recommend the use of latches in FPGA/CPLD designs, as they may lead to timing problems.
WARNING:Xst:737 - Found 1-bit latch for signal <1>>. Latches may be generated from incomplete case or if statements. We do not recommend the use of latches in FPGA/CPLD designs, as they may lead to timing problems.
WARNING:Xst:737 - Found 1-bit latch for signal <0>>. Latches may be generated from incomplete case or if statements. We do not recommend the use of latches in FPGA/CPLD designs, as they may lead to timing problems.
WARNING:Xst:737 - Found 1-bit latch for signal <2>>. Latches may be generated from incomplete case or if statements. We do not recommend the use of latches in FPGA/CPLD designs, as they may lead to timing problems.**
I wrote this code:
...ANSWER
Answered 2021-May-15 at 09:43As has been stated in the comments, you don't assign a value to all your output signals from the Case statement for each case. As the extract from the language standard can use language that is bit technical and opaque, I will try to write an explanation that is beginner friendly.
You case statement has seven outputs, Z(0..2) and Znot(0..3). Your process is of a type known as combinatorial (i.e. it is not clocked). The standard description of this structure would be to assign all outputs, for all cases. If you look at your first evaluation (when = "000") you can see that you are only assigning values to Z. This implies that you want Znot to retain its previous value, which implies a memory element. A non-clocked memory element is called a Latch.
The reason you get a warning is that Latches violate synchronous design practices. FPGAs are designed to work synchronously. The tools know this, and since in 99% of cases a latch is unintended, will raise a warning. The reason they don't raise an error is that there are some corner cases where a latch is intended, but this is for expert use only.
The correct way to imply a memory element is to use a register. In this case, to imply this would be to drive your process with a clock. If that is not desirable then explicitly state the desired value for every output in every case.
QUESTION
I have a gradle test task which runs a list of tests from a given file. Sometimes, any particular test execution simply gets stuck and does not move on to execute the next test(s) in the list.
For this, I am trying to add a java agent which will detect timeouts in each test execution and calls System.exit() in this case. (I know calling System.exit() seems to be a rash decision, but throwing exception does not seem to stop the test execution) The java agent uses byte-buddy advices for doing this.
...ANSWER
Answered 2021-May-13 at 11:23The OP said that my comment concerning security manager helped him find the root cause, so I am converting it into an answer:
As is documented, System.exit()
will not shut down the JVM if there is a security manager stopping it from doing so. In that case you should see a SecurityException
, though.
A discussion in Gradle issue #11195 mentions a problem that Kafka sporadically exits unexpectedly and suggests a security manager policy for Spring-Kafka stopping it from doing so. This was committed to Spring-Kafka, but - if I understand correctly - not to Gradle.
Another edge case is shutdown hooks: The thread invoking System.exit()
blocks until the JVM terminates. If a shutdown hook submits a task to this thread, it leads to a deadlock.
QUESTION
I have some code I have been putting on an ESP8266-12e board. Until recently it always worked fine. Now though when I finish uploading the code the blue light on the ESP8266-12e is staying on. I have tried it on two different board and the blue light stay on on both. I can't figure out what I changed in the code. I have decided to put it up and have everyone look at it and let me know what I may be missing. I hope someone can find something.
My code:
...ANSWER
Answered 2021-May-12 at 19:18So I got the blue light to go off. Instead of pinMode(D4,INPUT); and digitalWrite(D4,LOW); D4 is pin 16 which is the wake pin. So I had to define it thus #define LED3 16 and then pinMode(LED3,INPUT); and digitalWrite(LED3,LOW); I will change my original code to reflect these changes.
QUESTION
My Java multi-threading code is like the following. I expected if I use n threads (n < available cores), the total execution time will be 1/n of that using a single thread. But the experiment results don't demonstrate this: 4128 ms for 1 thread, 2200 ms for 2 threads, 3114 ms for 3 threads, 3031 ms for 4 threads.
...ANSWER
Answered 2021-May-10 at 06:35I'm not sure I can say anything specific about your timings, since it's still not clear how did you measure/calculate the numbers exactly, but you are right, "multithreading does not give a linear speedup to the number of threads...1/n" in most of the cases. Why?
I'm sure you have heard about Amdahl's law (https://en.wikipedia.org/wiki/Amdahl%27s_law). You can achieve "1/n" only if you don't have any sequential part of the program, a portion of the program that cannot be parallelized. But even if your own code/business logic/algorithm (or its portion to be parallelized) doesn't have such part, there are the underlying software and hardware layers that execute your code and these layers can introduce some sequential parts because of contention on some resources. For example, you can pass only one Ethernet packet at a time over a single-mode fiber or over a single twisted pair; your HDD can write data in only one position of its magnetic heads at a time; you have sequential access to the main memory because of the front-side bus and the memory bus; L2/L3 cache invalidation takes additional work to be done to be synchronized; a translation lookaside buffer (TLB) miss leads to walking to the main memory (see above about the front-side bus and the memory bus); to allocate a new object in JVM in the heap (when Thread-local allocation buffers (TLABs) is full) some internal synchronization required; you can get stop-the-world pauses on GC while compaction, which looks like a sequential portion of your code; classloading and JIT's activity add their sequential-like parts to the application; a 3rd party library may have some synchronization on a static value; etc., etc.
So, you can see "1/n" only in very very simple cases when not your application code, nor the underlying levels have any shared resources used. Here is an example
QUESTION
My Spring Boot REST endpoint returns HTTP status immediately but sometimes waits 60 seconds before returning the result.
This is caused by a Feign-proxied request's headers being altered (Transfer-Encoding
being replaced with Content-Length
)
The context and results of the investigation are detailed below.
- A (Spring Boot + Feign + Tomcat) -> Traefik -> B (Rest resource, Spring Boot + Tomcat)
- Traefik & B always respond immediately, A always returns the 200 status code immediately.
- Based on unknown criteria, A uses a KeepAlive stream and returns only after precisely 60 seconds (max idle thread?).
- B uses the
Transfer-Encoding: chunked
header, but Traefik replaces it withContent-Length
depending on unknown criteria. - The pause comes from a KeepAliveStream not being closed. I found several workarounds/solutions, but I'd love to have an explanation also.
- Removing the
Content-Length
header solves the issue. Debugging sun.www.net.HttpClient confirms that having aContent-Length
header triggers the use of a KeepAlive stream. - Calling A with the
Connection: close
header seems to solve the issue (same reason: this prevents the use of the KeepAliveStream). - Replacing Tomcat with Jetty in A seems to solve the issue, as it seems to rely on other HTTP libs.
- Replacing A's Feign's Apache HttpClient with OkHttp solves the problem.
- Removing the
- Why doesn't Feign/Tomcat/HttpClient close once the whole body is available (which is immediately)?
- Bonus question: Why/When/Based on what does Traefik alter the headers, and what are the rules?
One of our latest tests was to use -v
with curl and we saw this while A was pausing:
ANSWER
Answered 2021-Apr-27 at 10:49We've finally understood the mechanism that leads to the issue.
A -> Traefik -> B
- B returns a list of objects with a ZonedDateTime field (
"validFrom":"2021-12-24 23:59:57+01:00"
) and the headerTransfer-Encoding: chunked
. - Traefik replaces the
Transfer-Encoding: chunked
with aContent-Length
, computed from the body of the request. - A receives the response, deserializes the objects, then reserializes them but in the UTC timezone (
"validFrom":"2021-12-24 22:59:57Z"
), but it reuses theContent-Length
from Traefik without recalculating it.
As a consequence, the body from is shorter than the announced Content-Length
(each ZonedDateTime takes five bytes less when A sends it than when Traefik computes the content length).
The client however has been announced a Content-Length
and is waiting for the missing bytes.
The solution we have in mind right now is to tell Feign and its calling controller that it returns a ResponseEntity
instead of a ResponseEntity>
.
Pros:
- B's response is returned as-is, so no more problem due to a varying content length.
- A does not spend CPU-time deserializing then immediately reserializing the response.
Cons:
- The OpenApi doc of A won't show the type of return (unless the Open API annotation allow to specify the return model). That's what I'll test later today.
QUESTION
I'm confused how std::jthread::get_stop_token
is designed to work, because it seems to have an inherent race condition.
Namely, the executing thread can't simply call std::jthread
on itself (as in this example) because it has no guarantee that the std::jthread
object is actually constructed by the time that it begins executing. It seem to me that for a thread to use its own get_stop_token
, it requires (at the very least) an extra event (like std::latch
) solely to synchronize against its own construction.
However, I do not see any examples or mentions of this issue online, and so it seems to me that this may not be the intended usage. It does seem rather clunky and error-prone, as well as potentially inefficient as it requires the worker thread to block on the main thread before proceeding.
So how is get_stop_token
supposed to be used?
Is there a simple example of the proper, intended usage of std::jthread::get_stop_token()
?
ANSWER
Answered 2021-Apr-22 at 08:19It appears from the example from here that get_stop_token
is actually not meant to be used by the client code. It is called behind the scenes by the std::jthread
and passed to the function called by std::jthread
. It appears it is the way it's got to be done
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