The maximum size of UDP payload that, most of the time, will not cause ip fragmentation is MTU size of the host handling the PDU (most of the case it will be 1500) – size of the IP header (20 bytes) – size of UDP header (8 bytes) 1500 MTU – 20 IP hdr – … Read more
Casting to int is notoriously slow. Maybe you’ve been living under a rock since x86-64, or otherwise missed that this hasn’t been true for a while on x86. 🙂 SSE/SSE2 have an instruction to convert with truncation (instead of the default rounding mode). The ISA supports this operation efficiently precisely because conversion with C semantics … Read more
If you have a sorted array you can find such a pair in O(n) by moving two pointers toward the middle i = 0 j = n-1 while(i < j){ if (a[i] + a[j] == target) return (i, j); else if (a[i] + a[j] < target) i += 1; else if (a[i] + a[j] > … Read more
The database layout should not change when you add more data to it, so the user data should definitely be in one table. Also: Having multiple tables means that you have to create queries dynamically. The cached query plan for one table won’t be used for any other of the tables. Having a lot of … Read more
How do I see what inside the function is making the code take so long (Should I even use cProfile?) Yes, you can use cProfile but the way you asked the question makes me wonder if line_profiler (third party module, you need to install it) wouldn’t be a better tool. I’m using the IPython/Jupyter bindings … Read more
Never call DataFrame.append or pd.concat inside a for-loop. It leads to quadratic copying. pd.concat returns a new DataFrame. Space has to be allocated for the new DataFrame, and data from the old DataFrames have to be copied into the new DataFrame. Consider the amount of copying required by this line inside the for-loop (assuming each … Read more
Ok, so you want to know how it behaves at the lower level… Let’s have a look at the bytecode then! EDIT : added the generated assembly code for AMD64, at the end. Have a look for some interesting notes. EDIT 2 (re: OP’s “Update 2”): added asm code for Guava’s isPowerOfTwo method as well. … Read more
I don’t believe there are any performance gains from using a readonly field. It’s simply a check to ensure that once the object is fully constructed, that field cannot be pointed to a new value. However “readonly” is very different from other types of read-only semantics because it’s enforced at runtime by the CLR. The … Read more
I’m ignoring the issue that your benchmarking might be flawed, and taking the result at face value. Is it the compiler or is it at the hardware level? That latter, I think: if (a != 0 && b != 0) will compile to 2 memory loads and two conditional branches if (a * b != … Read more