docs: explain CUDA 11 compilation [no ci] (#16824)

This commit is contained in:
Johannes Gäßler
2025-11-06 08:14:35 +01:00
committed by GitHub
parent 6db3d1ffe6
commit 22c8c3c6ad

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@@ -178,6 +178,48 @@ GeForce RTX 3070 8.6
cmake -B build -DGGML_CUDA=ON -DCMAKE_CUDA_ARCHITECTURES="86;89"
```
### Overriding the CUDA Version
If you have multiple CUDA installations on your system and want to compile llama.cpp for a specific one, e.g. for CUDA 11.7 installed under `/opt/cuda-11.7`:
```bash
cmake -B build -DGGML_CUDA=ON -DCMAKE_CUDA_COMPILER=/opt/cuda-11.7/bin/nvcc -DCMAKE_INSTALL_RPATH="/opt/cuda-11.7/lib64;\$ORIGIN" -DCMAKE_BUILD_WITH_INSTALL_RPATH=ON
```
#### Fixing Compatibility Issues with Old CUDA and New glibc
If you try to use an old CUDA version (e.g. v11.7) with a new glibc version you can get errors like this:
```
/usr/include/bits/mathcalls.h(83): error: exception specification is
incompatible with that of previous function "cospi"
/opt/cuda-11.7/bin/../targets/x86_64-linux/include/crt/math_functions.h(5545):
here
```
It seems the least bad solution is to patch the CUDA installation to declare the correct signatures.
Replace the following lines in `/path/to/your/cuda/installation/targets/x86_64-linux/include/crt/math_functions.h`:
```C++
// original lines
extern __DEVICE_FUNCTIONS_DECL__ __device_builtin__ double cospi(double x);
extern __DEVICE_FUNCTIONS_DECL__ __device_builtin__ float cospif(float x);
extern __DEVICE_FUNCTIONS_DECL__ __device_builtin__ double sinpi(double x);
extern __DEVICE_FUNCTIONS_DECL__ __device_builtin__ float sinpif(float x);
extern __DEVICE_FUNCTIONS_DECL__ __device_builtin__ double rsqrt(double x);
extern __DEVICE_FUNCTIONS_DECL__ __device_builtin__ float rsqrtf(float x);
// edited lines
extern __DEVICE_FUNCTIONS_DECL__ __device_builtin__ double cospi(double x) noexcept (true);
extern __DEVICE_FUNCTIONS_DECL__ __device_builtin__ float cospif(float x) noexcept (true);
extern __DEVICE_FUNCTIONS_DECL__ __device_builtin__ double sinpi(double x) noexcept (true);
extern __DEVICE_FUNCTIONS_DECL__ __device_builtin__ float sinpif(float x) noexcept (true);
extern __DEVICE_FUNCTIONS_DECL__ __device_builtin__ double rsqrt(double x) noexcept (true);
extern __DEVICE_FUNCTIONS_DECL__ __device_builtin__ float rsqrtf(float x) noexcept (true);
```
### Runtime CUDA environmental variables
You may set the [cuda environmental variables](https://docs.nvidia.com/cuda/cuda-c-programming-guide/index.html#env-vars) at runtime.