You can achieve this by creating a third array of dtype uint8, plus a bool array (which together are more memory efficient that one uint16 array). np.putmask is useful for avoiding a temp array. a = np.array([100, 200, 250], dtype=np.uint8) b = np.array([50, 50, 50], dtype=np.uint8) c = 255 – b # a temp uint8 … Read more
Integer overflow is the canonical example of “undefined behaviour” in C (noting that operations on unsigned integers never overflow, they are defined to wrap-around instead). This means that once you’ve executed x + y, if it overflowed, you’re already hosed. It’s too late to do any checking – your program could have crashed already. Think … Read more
This answer assumes that float is an IEEE-754 single precision float encoded as 32-bits, and that an int is 32-bits. See this Wikipedia article for more information about IEEE-754. Floating point numbers only have 24-bits of precision, compared with 32-bits for an int. Therefore int values from 0 to 16777215 have an exact representation as … Read more
I don’t know about studies and statistics, but yes, there are definitely optimizations taking this into account that compilers actually do. And yes, they are very important (tldr loop vectorization for example). Besides the compiler optimizations, there is another aspect to be taken into account. With UB you get C/C++ signed integers to behave arithmetically … Read more
Yes, but… It is certainly possible, but it is usually nonsensical (for any program that doesn’t use billions of these numbers): #include <stdint.h> // don’t want to rely on something like long long struct bad_idea { uint64_t var : 40; }; Here, var will indeed have a width of 40 bits at the expense of … Read more
Here is what the program does at each step: 1 * 10 = 10 10 * 11 = 110 110 * 12 = 1320 1320 * 13 = 17160 17160 * 14 = 240240 240240 * 15 = 3603600 3603600 * 16 = 57657600 57657600 * 17 = 980179200 980179200 * 18 = 463356416 463356416 … Read more
This was likely a combination of factors: The big languages prior to Java used unchecked arithmetic. Well-known algorithms prone to numerical overflow tended to account for the potential overflow already without relying on checked arithmetic. Checked arithmetic introduces significant overhead in algorithms making heavy use of arithmetic instructions, which would put Java at a substantial … Read more
This is a really odd VBA quirk. I’m amazed I’ve never bumped into this. Dim x As Long x = 24 * 60 * 60 ‘ Overflow x = 32767 + 1 ‘ Overflow. x = 32768 + 1 ‘ Works fine! So it looks like the * and + operators return an Integer in … Read more
As pointed out by @Xeo in the comments (I actually brought it up in the C++ chat first): Undefined behavior really means it and it can hit you when you least expect it. The best example of this is here: Why does integer overflow on x86 with GCC cause an infinite loop? On x86, signed … Read more
Math.addExact throws exception on overflow Since Java 8 there is a set of methods in the Math class: toIntExact(long) addExact(int,int) subtractExact(int,int) multiplyExact(int,int) …and versions for long as well. Each of these methods throws ArithmeticException if overflow happens. Otherwise they return the proper result if it fits within the range. Example of addition: int x = … Read more