} std::modulus The C++ standard library provides a specialization of when T is not specified, which leaves the parameter types and return type to be deduced. We would say this as A modulo B is equal to R where B is referred to as the modulus. This is because the right shift , just like any other integer division, truncates, and thus rounds downwards. You can follow any responses to this entry through the feed. Is that what you want? I could of course just stop at this point. One can predict the general result one expects from such a comparison.
For most cases this is not an optimisation that is worth considering, and certainly not worth calculating your own shortcut operation especially if it still involves divide or multiply. As you mentioned, modulo on a signed dividend may not be optimized to a mask operation. This entry was posted on Tuesday, February 8th, 2011 at 9:21 am and is filed under , ,. Thus this suggests a simple optimization to the algorithm. .
The C language does not support this directly, but my compiler will generate good code if you declare a local 64-bit integer and immediately right-shift it. That said, I'd suggest doing some research and performance profiling on your intended platforms to get a clear idea of the performance constraints you're under. Jamie ImagineNation wrote: Hi Steven; You made a slight error. The following example demonstrates the behavior of the remainder operator for float and double operands: Console. It multiplies the right operand with the left operand and assigns the result to the left operand.
As in, you have a valid array index, and you want to compute the next array index in a descending order. For example, the following C++ code find whether the number in an array is even or odd by using the modulus. Tutorials, testimonials, and examples are continuously checked to avoid delusion, but we cannot take complete responsibility of all programs on Xiith. You can , or from your own site. User-defined types can the % operator. You seem to be correct, thank you. If yes, then the condition becomes true.
Due to the floor function, the quotient is always rounded downwards, even if it is already negative. I don't think this is what the original poster was asking about, though. My recollection is that it was a pseudo register located under the register pull down. Well I found myself in just such a situation recently. Modulo remainder is one of the two results that any reasonable processor or compiler library outputs for a division operation.
In the first attempt, you first compute the seconds then minutes, hours, days. In adult speak, the modulo of 26 over 8 is 2. Thus this suggested an improvement that would make the code a lot more portable — and that is to use the. Thus, the sign of the remainder is chosen to be nearest to zero. An earlier commenter had implied this in mentioning the standard div function.
In this C program, we will learn how can we find the remainder of two integer numbers without using modulus % operator? In other words the modulus operator is functionally equivalent to three operations. As it would be very difficult to give everyone 3. However examination of attempt 2 shows that further optimizations are possible by observing that if seconds is a 32 bit variable, then days can be at most a 16 bit variable. To demonstrate what I mean, some background information is in order as to how this blog posting came about. Again we multiply the decimal part 0. I'd feel bad for the next guy who has to look at the code otherwise. Modulus function object class Binary function object class whose call returns the result of the modulus operation between its two arguments as returned by operator %.
Jacob is correct to point out that the division by 60 or modulo 60 operation can also be transformed into a multiplication by the reciprocal of 60 with scaling. I thus sat down to write my own code. Modular arithmatic, for instance, is very handy for generating. The most important results to remember from all this are: 1 One can easily derive integer approximations that can deliver flawless exact integer results in all cases provided that the constant divisor is small. Since we're talking about a range of 0 to 5, I can easily just show you that it's right for all values of i. There may be much more productive places to spend your optimisation effort.
This should be a compiler optimization issue. It can take any 32-bit, signed or unsigned. However, other conventions are possible. That's the definition of modulo - it doesn't suck. Code that's written awkwardly to optimize for performance is hard to debug and hard to maintain. Within an expression, higher precedence operators will be evaluated first. Jeff V: I see a problem with it! It is even simpler to split an integer up to 999 into hundreds, tens and units without mod or div with an ordinary 32-bit processor and no tricks.
Write code which takes platform limitations into account, of course. You keep doing an extra +1! I did think it was odd that division was faster than mod, they are the same operation. Despite its widespread use, truncated division is shown to be inferior to the other definitions. For instance, if I want to ensure that a result is within the range of my index, I would much prefer to be able to simply take the answer % my array count rather than handling negative answers separately. Browse other questions tagged or.