You are tasked with optimizing a piece of code containing nested loops...
- Move calculations outside of the loops.
- Replace inner loop with a lookup table.
- Inline the inner loop calculations.
- Prefetch data before processing in the inner loop.
A lookup table can be used to store pre-computed results of complex calculations. By replacing the inner loop's calculations with lookups from this table, one can often achieve significant speedups, especially if the same calculations are being performed repeatedly.
What is the purpose of the this pointer in C++?
- To return the current object's address.
- To point to global variables.
- To create a new object.
- To delete the current object.
In C++, the this pointer is used within a class's member function to refer to the invoking object of that function. It's an implicit parameter to all member functions and contains the memory address of the current object, allowing for operations on the calling object itself.
When passing parameters by reference, which symbol is used to denote reference in C++?
- #
- @
- &
- %
In C++, the ampersand (&) is used to denote that a parameter is being passed by reference. This allows the function to directly access and modify the actual argument's memory location.
You are tasked with enhancing the performance of a critical path in an application. You identify a function that is called very frequently as a potential optimization target. Which specific aspect of the return statement could you focus on to possibly improve performance, especially considering modern C++ standards?
- Returning by value.
- Returning by pointer.
- Using return in a loop to optimize iterations.
- Returning by reference or moving.
In modern C++, when considering performance-critical paths, it's beneficial to understand the difference between returning by value and returning by reference or using move semantics. Especially with the advent of Rvalue references in C++11, returning by reference or moving can avoid unnecessary copies and lead to significant performance improvements. Returning by pointer is less idiomatic and might not convey ownership semantics clearly.
In the context of floating-point representation, what is the role of the mantissa?
- Determines the sign
- Determines the exponent
- Stores the actual digits
- Determines the base
In floating-point representation, the number is typically represented as: (-1)^sign * mantissa * (base^exponent). The mantissa is responsible for storing the actual digits of the floating-point number, while the exponent determines the position of the decimal point and the sign determines its sign.
The first commercially available C++ compiler was named _______.
- CFront
- Clang
- GCC
- Turbo C++
CFront was the first commercially available C++ compiler. It was developed by Bjarne Stroustrup at Bell Labs as a front-end to the C compiler. This compiler played a crucial role in the early evolution and popularization of C++.
How does C++ treat an enum regarding its type and size?
- As a float type with fixed size
- As an integer type with variable size
- As a class with member functions
- As a boolean type
Enums in C++ are treated as integer types. Their actual size can vary based on the compiler and the number of values they hold, but typically, they have the size of an int. C++11 introduced scoped enumerations (enum class) that offer better type safety, but fundamentally, they're still integers.
If a break statement is encountered in a nested loop, it will exit _______.
- the outermost loop
- the innermost loop
- the function
- the program
When a break statement is encountered within a nested loop, it only exits the loop in which it's directly contained, i.e., the innermost loop. It does not affect any outer enclosing loops.
What is a friend function in C++?
- A function that always returns a friend object.
- A private function of a class.
- A function that can access private members of a class.
- A function that can only be called within its class.
A friend function in C++ is a special function that, although not a member of a class, has access to its private and protected members. This is used to allow non-member functions and other classes to access such members.
Consider a large-scale software project that heavily utilizes templates and generic programming. With an impending deadline, the compilation time is becoming a significant bottleneck. Which C++ feature/technique might be best suited to reduce compilation times without altering runtime performance?
- Decrease template depth
- Explicit template instantiation
- Use dynamic polymorphism
- Use of inline functions
Explicit template instantiation can help reduce compilation times by instructing the compiler to instantiate the templates in a specific source file rather than whenever they're used. This can help reduce redundancy and speed up the compilation of large projects that heavily rely on templates.