SIMD: A C repository from andrewchan2002

README for SIMD and Non-SIMD Convolution Calculation

This project demonstrates the use of SIMD (Single Instruction, Multiple Data) instructions for optimizing convolution calculations between two matrices of floating-point numbers. The project contains three main C programs: init.c, simd.c, and simd_t.c, each showcasing different methods of computation with varying levels of optimization.

Program Overview

init.c (Baseline Convolution Calculation):
- Implements a basic non-SIMD convolution operation between two 400x198 matrices stored in a file (data.txt).
- The result is stored in a 1D array ans[200].
- The program measures and prints the elapsed computation time.
- Outputs the result to output.txt.
simd.c (SIMD Convolution without Timing):
- Utilizes SIMD instructions (_mm_mul_ps and _mm_add_ps) to perform vectorized convolution calculations.
- The arrays are aligned using __attribute__((aligned(16))) to ensure proper memory alignment for SIMD operations.
- The computation uses SIMD to speed up the operations by processing 4 floating-point values simultaneously.
- This version does not include time measurement.
- Outputs the result to output_simd_without_time.txt.
simd_t.c (SIMD Convolution with Timing):
- Similar to simd.c but includes time measurement using clock_gettime().
- Measures the time taken to perform the convolution with SIMD instructions.
- Outputs the computation time and the result to output_simd.txt.

File Descriptions

data.txt: Input file containing the floating-point numbers that will be processed. The file is expected to have 400 rows and 198 columns of float data.
output.txt: Output file from init.c containing the convolution results without SIMD optimization.
output_simd_without_time.txt: Output file from simd.c containing the results of the SIMD optimized convolution without time measurement.
output_simd.txt: Output file from simd_t.c containing the SIMD optimized convolution results and the elapsed time for the computation.

Compilation and Execution

Compiling: You can compile the programs using the provided Makefile. It generates three executable files: init.exe, simd.exe, and simd_t.exe.
```
make all
```

Running the programs: After compilation, run each program using the following commands:

./init.exe   # Runs the basic (non-SIMD) convolution
./simd.exe   # Runs the SIMD optimized convolution (without timing)
./simd_t.exe # Runs the SIMD optimized convolution with timing

Cleaning: To remove the compiled executables, run:
```
make clean
```

Performance Comparison

init.c: Baseline implementation using standard loops for convolution.
simd.c and simd_t.c: Use SIMD instructions for improved performance, with simd_t.c additionally measuring the elapsed time.

Dependencies

GCC: Ensure you have GCC installed with support for SSE (SIMD) instructions.
C Standard Library: The programs rely on standard libraries (stdio.h, stdlib.h, string.h, time.h) and SIMD-specific headers (xmmintrin.h).

Notes

The data.txt file must be formatted with floating-point numbers and properly structured to fit the 400x198 matrix size.
Ensure that the system supports SIMD (SSE) instructions for simd.c and simd_t.c to execute correctly.

Future Improvements & Result

Expand the program to support larger matrices.
Explore AVX or AVX-512 instructions for further optimization.
Compare SIMD performance across different platforms.
NonSIMD version: Elapsed time: 0.025616 seconds
SIMD version: Elapsed time: 0.011092 seconds

andrewchan2002/SIMD