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C++ vs Python in terms of energy consumption

From: Phil Bouchard <boost_at_[hidden]>
Date: Thu, 7 Nov 2024 19:23:33 -0500
Greetings,

This is not a proposal but an important factor people dismiss which the
power consumption of programming languages in this AI era. Basically
there would be no power consumption issues if C++ was used instead of
Python for AI algorithms.

Here's a quick analysis from ChatGPT itself:

The exact percentage by which C++ outperforms Python in terms of CPU
power consumption varies widely based on the specific task, but here are
some general benchmarks and factors to consider:

### Typical Performance Difference
- **CPU-Bound Computations**: For CPU-intensive tasks (e.g.,
mathematical computations, data processing), C++ can be **2 to 100 times
faster than Python**. This translates to a potential **50-99% reduction
in CPU time**, depending on the complexity of the operation.
- **Memory Management and Large Loops**: When memory usage and
loop-intensive operations are involved, C++’s lower-level management can
often result in **5-20 times faster performance** than Python, or an
**80-95% CPU time reduction**.
- **I/O-Bound Tasks**: For tasks primarily limited by I/O operations
(like reading/writing files or network requests), the difference might
be smaller, around **10-30%**. Here, other factors like disk or network
speed are more limiting, and language efficiency plays a lesser role.

### Example Benchmark Percentages
Some benchmark studies and tasks provide a sense of the variation in
percentage gains:
1. **Numerical Computations** (e.g., matrix multiplications): Python
with NumPy can be within **10-20%** of C++ speed, but without libraries,
C++ may use **90% less CPU time**.
2. **String Manipulation**: C++ can be around **5-10 times faster**, or
reduce CPU time by **80-90%**, compared to Python, especially if Python
relies on interpreted loops rather than optimized library functions.
3. **Machine Learning Models**: Using libraries like TensorFlow (which
relies on C++ backends), Python might be within **5-10%** of the CPU
usage of a native C++ implementation, as the computational work is
already optimized in C++.

### Why the Variation?
The percentage difference depends on:
- **Nature of the Task**: Computation-heavy tasks see the biggest
performance gap.
- **Use of Optimized Libraries**: Python’s gap shrinks if it uses
libraries with C/C++ backends.
- **Data Size and Algorithm Complexity**: As data and complexity grow,
the C++ advantage generally increases.
- **Python’s Interpreter Overhead**: For small scripts, the
interpreter’s constant overhead can make Python relatively slower.

### General Rule of Thumb
For purely CPU-bound tasks, **expect C++ to be 80-95% more CPU-efficient
than pure Python**. If using optimized libraries in Python, the gap can
narrow, potentially resulting in only a **10-20% efficiency loss**
compared to C++.

This range highlights how language choice impacts CPU consumption, with
C++ typically outperforming Python significantly in high-performance
applications.


Sincerely,

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Received on 2024-11-08 00:23:38