Despite being one of the fastest programming languages, you might experience your C++ programs running slower than expected. But, it is not a big deal as you can easily “Optimize Slower Running C++ Codes”.
While working with the C++ language, sometimes, we forget that the speed of a program execution doesn’t solely depend on the language. But it also highly depends on how the code is written and compiled.
However, if you’re struggling with C++ assignments or need expert guidance, you can always seek help from our C++ Homework Help service to get personalized assistance.
In this article, we will first share some common reasons for which you might experience a Slower-Running C++ Code. And later, we will talk about some effective optimization tips. So, let us start our discussion.
TL;DR: Optimizing Slower Running C++ Codes
Aspect | Summary |
What is the issue? | C++ programs may run slower than expected despite being a fast language, mainly due to inefficient code structure and memory handling. |
Common Causes | Inefficient or Nested Loops, Unnecessary Memory Allocation (e.g., new/delete in loops), Cache-inefficient Code (non-sequential array access) |
Debugging Tips |
|
If Not Optimized | Higher CPU load and system heat, More battery consumption, Frequent lags, freezes, and slow performance, and reduced available RAM over time. |
What Are Some Common Reasons Behind C++ Code Run Slower?
For the C++ language, experts say, it is ‘Close to Hardware’. This is because of its remarkable execution speed. But, with the same C++, you might face a ridiculously slow code execution speed for some common reasons.
In this section, we will talk about some common mistakes that occur due to the programmer.
1. Inefficient Loops:
Loops are the backbone of any program. When you develop an inefficient loop, it not only reduces the speed of that program but also consumes a lot of memory and creates implications for other programs.
#include <iostream>
#include <vector>
using namespace std;
int main()
{
vector<int> arr(100000, 5);
long long sum = 0;
for (int i = 0; i < arr.size(); i++) // An Inefficient Nested Loop
{
for (int j = 0; j < arr.size(); j++)
{
sum = sum + arr[j]; // More Memory Consumption
}
}
cout << sum << endl;
return 0;
}
In the above code, a nested loop has been created to add some values to an array. But, for that purpose, we can use a single for loop. That will also fulfill the need. But here, the Nested For Loop is making it inefficient.
2. Unnecessary Memory Allocation:
Memory in programming is very expensive. So, we have to be careful while losing it. Unnecessary Memory Allocation by any means reduces the space for future programs, which will become slower then.
#include <iostream>
#include <vector>
using namespace std;
int main()
{
for (int i = 0; i < 1000; i++)
{
int* zap = new int[1000]; // Repeated Memory Allocation
delete[] zap; // Repeated Memory Deallocation
}
return 0;
}
In the above code snippet, a For Loop is used to create Dynamic Memory using the NEW Keyword. And the Memory Allocation and Deallocation have been done here 1000 times, which is a misuse of the memory.
3. Cache Consuming Code:
Cache is an important aspect in modern computers for their high speed. If your program is hopping in the memory instead of going in a sequence, then certainly more caches will get included in the CPU.
#include <iostream>
#include <vector>
using namespace std;
int main()
{
static int zap[100][100];
long long sum = 0;
// Iteration Is Done By Column-Wise
for (int j = 0; j < N; ++j)
for (int i = 0; i < N; ++i)
sum = sum + zap[i][j];
return 0;
}
In the above code, the iteration of a 2D array is done column by Column, which forces the program to access memory addresses sequentially. Instead, we can iterate through the 2D array by rows in a sequential manner.
What Are Some Tips To Fix Slower Running C++ Programs?
As the common causes behind C++ code slowing down have become clear to us, we can now move ahead with some Debugging Methods or Tips. In this section, we will discuss 5 effective debugging techniques.
These debugging tips are very effective to make your future C++ code more optimized. So, let us start.
But before diving deep into these debugging tips, it’s essential to have a good grasp of the basic syntax rules in C, which lay the groundwork for understanding how C++ evolved.
Tip 1: Use Optimized Loops In C++ Programs
Programming Loops are very sensitive, and almost every program has some kind of loop. The more extra work you write inside any C++ loop, the more memory space will be allocated.
Most of the time, a beginner mistakenly writes so much information inside a loop and creates a Nested Loop or Repetitive Loop, which leads to an exponential slowdown of the entire system.
To make your C++ loops more optimized and perfect, the following tips can be used.
- As much as possible, try not to use any Nested Loops in any C++ program.
- If there is any constant calculation in your program, put it outside of the loop range.
- You should not use any time-consuming operations like Input and Output inside any loop.
Tip 2: Reduce Memory Allocation In C++
Memory Allocation is the costliest thing in any programming. Your goal should be to smartly create a memory, use it, and dump it. A large memory-consuming program is eating up the space for your future programs.
Whenever you are using NEW, DELETE, or resizing any VECTOR, the C++ compiler interacts with the Heap Memory, which itself takes ample time. So, try to poke the memory as little as possible in your C++ code.
Improper memory allocation can lead to memory leaks in C++, which is a common issue faced by beginners.
You can use the following tips to understand the proper and optimized way of memory allocation.
- If there is any Temporary Array, then go with the Stack Allocation rather than Dynamic.
- Never try to allocate and deallocate memory inside any C++ loops.
- Try to clean a VECTOR container and reuse it rather than creating a new container for a new job.
Tip 3: Use Proper C++ Compiler Flags
If you are executing any IDE where a Terminal is present, then this tip can be useful for you. You can give the full potential to your C++ compiler to provide its best during code compilation.
Sometimes, a well-written code takes time just because the C++ compiler is not executing at its full potential. For that, you can use some Compiler Flags like the following to aggressively compile the code.
Command: g++ -O2/-O3/-Ofast name.cpp -o program
- To do Balanced Optimization between Speed and Safety, the -O2 Compiler Flag is used.
- If you prefer Maximum Speed and Performance over Safety, then the –O3 Flag is used.
- For Scientific Computation, the –Ofast flag is used, which ignores Strict Standards.
Tip 4: Picking Up Efficient Data Structure For C++ Programs
Another important aspect where beginners create a mess is the Data Structure. There are multiple Data Structures present, and picking up the right Data Structure for the right need is quite difficult.
If you picked up the wrong Data Structure for a different need, your code will consume a lot of memory, and its speed will be reduced significantly. And if you have saved the code for a long time in an IDE, it can affect future code.
The following tips can become helpful while choosing a Data Structure for a certain need.
- If there is any General-purpose task, they always prefer the VECTOR for its speed.
- If you need any faster Lookups, then the UNORDERED version should be better than the normal MAP.
- You should not use LIST everywhere until there is a random insertion and deletion needed.
Tip 5: Develop Cache-Friendly C++ Code
Modern processors highly depend on the Cache. Caches store the recently used memory blocks in them. So, if your program is jumping from one memory address to another, then you should write it carefully.
As much as the memory address jump your program will do, that much of the load will be stored in the Cache. Instead, you have to try to jump the memory address in a sequential manner, which is less harmful.
You can check the following tips to develop a Cache-friendly C++ Code in the future.
- You should prefer the VECTOR over the LIST as the VECTOR stores memory in sequence.
- Until there is a huge need, try to avoid pointer dereferencing and linked list traversals in loops.
- You should access the arrays in the same order they are stored. This reduces memory jumps.
What Will Be The Implications If Slower Running C++ Codes Are Not Optimized?
In the end, if you think that Optimizing Slower-Running C++ Codes is useless and you keep executing more and more inefficient codes thereafter, the implications will be huge and irreversible.
Before we conclude our topic, let us check what some implications will be in that case.
- The CPU load will increase, and this will affect not only the code execution but also the entire system.
- Your system will consume more battery to keep all work going on and increase the hardware heat.
- You will witness frequent lags and freezes, regardless of the application you are working on.
- If the codes are not optimized, the RAM size will get shorter over time and cause issues.
- The codes that were earlier executing well will also start lagging as less space will be available.
Key Takeaways:
- Despite being one of the fastest programming languages, the C++ code can also lag due to development.
- Inefficient Loops, Unnecessary Memory Allocation, etc., are some common reasons behind slowing.
- Developing Cache-friendly Code, Choosing Efficient DS, and Loops are some debugging methods.
- Reducing Memory Allocation and Using Compiler Flags are also some alternative debugging ways.
