Why assignment arithmetic operations are faster

Assigning an int to a float, for example, is not a problem; the int is promoted to a float without loss of information no fractional part thrown out. If you use any of these operators on two operands of the same type, the result is that type.

Mixing the types causes automatic promotion. Modulo arithmetic is only allowed with integer types. When an int int-type is divided by another int, the result is an int. Simple you say? Yes, but that can trip you up and cause your program to give erroneous results. Let me show you in this example. Suppose you write a program to convert Fahrenheit to Celcius. See the programin module 2.

It must contain an assignment statement along the lines of. Regardless of the value of fahr that is used, celc will be assigned 0. How is that? Both of the literal constants 5 and 9 are stored by the compiler as integers. Integer division will give you 0 9 goes into 5 zero times , and 0 times anything is 0. In this case, it is an easy fix:.

It makes no sense that they be floats. But the result of the quotient on the lhs will be an int. To make this work the way you wish is:. We cast either the numerator or the denominator or both, but NOT the quotient.

Now, a float divided by an int will give you a float as desired. You may not think mod arithmetic is so important, but it can be very useful. Privacy settings Decide which cookies you want to allow. You can change these settings at any time. However, this can result in some functions no longer being available. Learn more about the cookies we use.

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Remember that Users cannot distinguish anything smaller than 1E-2 seconds. So, how many iterations will it take to make 50 nanoseconds noticeable? With modern processors, a plethora of iterations must be performed in order to gain significant time from one of these instruction level changes.

So the return on investment the time it takes you to optimize these instructions is not worthwhile. The ROI is only high when the program performance impacts sales or requirements such as critical systems.

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Ask Question. Asked 6 years, 7 months ago. Active 6 years, 7 months ago. Viewed 1k times. I have this peace of code and I would like to make it as fast as possible.

And now I don't really know if that was the best thing to do. So, what is faster? Also thank you all for the comments, learned a lot. Improve this question. Rafael Fontes. Rafael Fontes Rafael Fontes 8 8 silver badges 18 18 bronze badges. Chances are good that compiler optimization will make them both equal but in theory without any optimization, the second code is probably faster because 2x division and modulo is very slow compared to 1x and assignments.

Side note: register is obsolete — user Measure it. Here, the exponent is 3, and the expression can be read in any of the following ways:. Some exponents have their own unique pronunciations. Exponentiation is used frequently in many fields, including economics, biology, chemistry, physics, and computer science, with applications such as compound interest, population growth, chemical reaction kinetics, wave behavior, and public key cryptography. Any nonzero number raised by the exponent 0 is 1.

The order of operations is an approach to evaluating expressions that involve multiple arithmetic operations. The order of operations is a way of evaluating expressions that involve more than one arithmetic operation.

These rules tell you how you should simplify or solve an expression or equation in the way that yields the correct output. In order to be able to communicate using mathematical expressions, we must have an agreed-upon order of operations so that each expression is unambiguous.

For the above expression, for example, all mathematicians would agree that the correct answer is The order of operations used throughout mathematics, science, technology, and many computer programming languages is as follows:. These rules means that within a mathematical expression, the operation ranking highest on the list should be performed first.

Multiplication and division are of equal precedence tier 3 , as are addition and subtraction tier 4. This means that multiplication and division operations and similarly addition and subtraction operations can be performed in the order in which they appear in the expression.

In this expression, the following operations are taking place: exponentiation, subtraction, multiplication, and addition. Following the order of operations, we simplify the exponent first and then perform the multiplication; next, we perform the subtraction, and then the addition:. Here we have an expression that involves subtraction, parentheses, multiplication, addition, and exponentiation. Following the order of operations, we simplify the expression within the parentheses first and then simplify the exponent; next, we perform the subtraction and addition operations in the order in which they appear in the expression:.

Since multiplication and division are of equal precedence, it may be helpful to think of dividing by a number as multiplying by the reciprocal of that number. Similarly, as addition and subtraction are of equal precedence, we can think of subtracting a number as the same as adding the negative of that number.

In other words, the difference of 3 and 4 equals the sum of positive three and negative four. To illustrate why this is a problem, consider the following:.

This expression correctly simplifies to 9. However, if you were to add together 2 and 3 first, to give 5, and then performed the subtraction, you would get 5 as your final answer, which is incorrect. To avoid this mistake, is best to think of this problem as the sum of positive ten, negative three, and positive two. Or, simply as PEMA, where it is taught that multiplication and division inherently share the same precedence and that addition and subtraction inherently share the same precedence.

This mnemonic makes the equivalence of multiplication and division and of addition and subtraction clear. Privacy Policy. Skip to main content. Numbers and Operations. Search for:. Introduction to Arithmetic Operations. Learning Objectives Calculate the sum, difference, product, and quotient of positive whole numbers. Key Takeaways Key Points The basic arithmetic operations for real numbers are addition, subtraction, multiplication, and division.

The basic arithmetic properties are the commutative, associative, and distributive properties. Key Terms associative : Referring to a mathematical operation that yields the same result regardless of the grouping of the elements.