blockchain – Chain Race: How to know the length of a chain in competition?

What happens if the 10% fork (chain A) now extracts a block and sends it to the network?

When a miner under construction over A has found a valid block, he will relay it to the rest of the network. By convention, suppose that the fork (chain A and chain B) has reached the height of the block N. This is how the different nodes in the chain will react.

  1. Nodes already use channel A: For them, this block N + 1 is a natural progression of the blockchain and therefore they will only add this block to their blockchain.
  2. Nodes using string B but having the block of string A: Some nodes might have received the string A block in height N after receiving the block in height N This block received later is not rejected, but is processed and kept on the disk in the format. Thus, when a block of height N + 1 is received from the version of the chain A, these nodes simply reverse the height string N and use the other block kept on the disk.
  3. Nodes with only the B string: When they receive a block of height A + 1 of the string A, these nodes will see that they have no parent. As a result, these nodes will query the parent block using the previousblockhash and see if that exists. Nodes with this block then pass this block to nodes that do not have it. When this block is received, these nodes will see that this string is the proof of the longest proof of the chain of work. They will now operate on channel A. The block located at the N height of the B-channel becomes out of date, but it is not ignored and remains on the disk.

How do they know this chain is longer?

Nodes accept the longest proof of the chain of work (in most cases, the longest chain). The nodes first synchronize the headers and check the proof of the work of the chain before asking the real blocks to the other nodes. When the version B nodes of the string receive the N + 1 block header of version A, they will see that the chainwork the received block is greater than that of the other string and will use it to query the block associated with it.

How do they know that the block is not part of DDoS attacks?

When they receive the block header, proof of work is checked first. So, if the attacker wants to spam the network with invalid blocks, he will have to do it with valid proof of work. This means spending a huge amount of energy like other miners, but not receiving a reward (the block having no ancestor, it will be rejected). If the node receives a block header with an invalid proof of work, the node that sent this block header will be placed on a blacklist after some attempts of this bad. This is actually the basis of the war program in the 90s, when it was used to prevent spam.

How to avoid the conditions of competition during the management of the UNIX process in C?

I'm trying to build a simple UNIX shell for educational purposes. My intention is to correctly manage the processes in the background, displaying a message at the end of the work via the SIGCHLD manager in the parent process. But my code seems to follow in a loop, creating child processes every time I add & to my order, for example: ls &

So, I guess there are alarming bugs about race conditions, since I'm getting the expected result when using gdb and go step by step in debug mode, but I can not pinpoint the places where I'm wrong. Do they use best practices for process management? (In my original code, I made sure to manage jobs through proper data structures and manage memory via freeso this is not a problem)

Code snippet for reproduction: (alternative mirror here)


int argLength = -1;
char** argVector;
int isBackground = 0;
int childPID = -1;
int parentPID = -1;

void printPrompt()
    printf("Shell~: $ ");

char* str_concat(char* s1, char* s2)
    int l1 = strlen(s1);
    int l2 = strlen(s2);
    char* op = (char*) calloc (l1 + l2, sizeof(char));
    for(int i=0; i 0)
                        printf("(bg)  %d finishedn", pid);

                    int status;
                    waitpid(pid, NULL, WUNTRACED);
                isBackground = 0;
    return 0;

There are 6 people in a competition where only 3 can win. What is the probability that a person wins?

There are 6 people in a contest – A, B, C, D, E, F.

Only 3 will be winners.

So, what is the probability that a particular person, say A, is a winner.

My friend said that the probability of being a winner is 50%. I thought they were wrong because there might be an application of permutations / combinations, but I am confused.

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Is it a competition?

Leave a square, $ ABCD $and an equilateral triangle, $ EFG $, be registered in a circle as indicated. They are symmetrical around an ordinate axis. Yes $ M $, $ N $ are the circles of $ BC $ and $ FG $, respectively, to prove (or refute) that $ BG $, $ MN $ and the partridge $ FG $ through $ C $ are simultaneous.

enter the description of the image here

Competition – Theme $ 75


You are looking for an order processing theme for the web hosting industry. note: this has nothing to do with the main billing systems, namely whmcs, blesta or clientexec.

We are looking for;
Current Order – Domain Registration, Transfer or Update NS
Register -> the customer can register and register
Payment (entered by credit card or PayPal – Select the method).
Invoice for purchase

Ideally, want a design of a page

Note: None of the billing panels mentioned above can have the same theme. So will reject.

The winner will have more work for that. I will give you these 5 days – until Friday to choose.

What is the analysis of the competition?

Hello friends,

I would like to know what is the analysis of competitors?

color – Draw the attention of the main button in competition with the header

I am looking for help with our primary color. We use blue as the primary color and we have placed it in the header to strengthen the brand identity.

On the other hand, blue is also our main button color. Setting up our CTAs was easy, until today.

With our list view, I tend to place it directly under the header. The problem: the focus is lost because the attention of the button is less efficient due to its immense use by the header.

Do you know how to replace the button or change the style to make it more attractive?

Putting it on the bottom right should be the last solution because we have reserved the bottom right corner for a chat / support button.

Thank you together 🙂

Example of the primary color problem

Update SharePoint List Items – Competition Using the REST API

I use the REST API to update the SharePoint (counter) list item. In my code when loading the form, I extract the number from the list and increment it by 1 & click on the submit button, I update the value of the number up to here & # 39; I reached.

A problem arises, if two users send the form at the same time, the counter value is incremented by 1 instead of 2 in the list.

Checked with etags. But I found that during the post if etag does not match get request etag, an error will be returned.

Is there any way to get this feature using the REST API by correctly incrementing the counter if more than 3 to 4 users submit the form?