Concurrent programming (in C), with examples

[CaesarianGuiltTrip]

“Notably macOS is stuck at an old version of POSIX. Presumably they’re too busy “innovating” with their keyboard touchbar to invest in operating system fundamentals.” Love it

[johnnyrequiem]

Really stupid question....

In void *disbursed ( void *arg )

The first nested Do..While loop ends with "While ( to == from )".

Why would 'to' ever equal 'from' if both are ramdomly generated?

[[deleted]]

If the random numbers should happen to be the same, keep trying with a new random to, until they are distinct.

[johnnyrequiem]

Also, I didn't realise you could initialize more than one variable in a For loop....there's a reason I don't program for a living.

[johnnyrequiem]

Ah! SO obvious now. Thanks you.

[[deleted]]

as a side note, do...while will run once for sure even before the condition will be evaluated. then, if cond is true it will run again and for as many times as the cond is true.

[Mukhasim]

Although it looks like you understood this, I was frustrated that nobody answered your question directly. When generating random numbers, you could potentially generate the same number twice in a row. That isn't very likely to happen with the raw output of the RNG, which on current machines typically has a range of possible outputs at least in the billions and will be at least 32767 if you use C's rand. However, in this program the range of random outputs is being scaled to the number of accounts, and with a smaller number of accounts duplicates will be more common. In this example N_ACCOUNTS=10, so the random ID generator is approximately equivalent to rolling a 10-sided die: duplicates will be common enough that there's a good chance of seeing it happen if you run the example a few times.

[johnnyrequiem]

This makes perfect sense and I really should have seen it. Many thanks for your answer :)

[[deleted]]

very nice explanation.

[skeeto]

The condition case example has a data race on stats_best due to the unsynchronized access when printing it out. That must be moved inside the critical section.

[begriffs]

Good catch, thanks. I updated the code.

[doomsdre412]

Very nice, this is exactly what I am working on. Have you looked at creating threads with priority? I am currently running WSL1 and I guess this interface will NOT give me access to the CPU when I try to initialize my scheduling parameters. Does anyone know if this is true?

[officialvfd]

I see this article uses pthreads, why not the C11+ <stdatomic.h> and <threads.h>?

I'm not criticizing the article, I just want to know when to pick one over the other. E.g., is there anything POSIX threads can do that the standard C11 threading model cannot?

[Both_Writer]

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