ewald 0.1.9

Ewald SPME force calculations
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144

//! We use this to automatically compile CUDA C++ code when building.

#[cfg(feature = "vkfft")]
use std::{
    env, fs,
    path::{Path, PathBuf},
};

#[cfg(feature = "vkfft")]
use cc;
#[cfg(feature = "cufft")]
use cuda_setup::build_host;
#[cfg(feature = "cuda")]
use cuda_setup::{GpuArchitecture, build_ptx};

fn main() {
    // Build non-FFT kernels that are used for both GPU FFT branches.
    #[cfg(feature = "cuda")]
    build_ptx(
        // Select the min supported GPU architecture.
        GpuArchitecture::Rtx3,
        &["src/cuda/kernels.cu"],
        "ewald",
    );

    // cuFFT-specifical host-side building
    #[cfg(feature = "cufft")]
    build_host(
        // Select the min supported GPU architecture.
        GpuArchitecture::Rtx3,
        &["src/cuda/cufft.cu", "src/cuda/kernels.cu"],
        "spme",
    );

    // VkFFT-specifical host-side building
    #[cfg(feature = "vkfft")]
    {
        // Our FFI files.
        println!("cargo:rerun-if-changed=src/cuda/vk_fft.cu");
        println!("cargo:rerun-if-changed=src/cuda/vk_fft.h");
        // This is the vkFFT header
        println!("cargo:rerun-if-changed=third_party/VkFFT/vkFFT.h");

        let out_dir = PathBuf::from(env::var("OUT_DIR").unwrap());

        // We set up a location to cache the compiled VkFFT library, as the location Cargo places
        // it in by default changes each build.
        let manifest_dir = PathBuf::from(env::var("CARGO_MANIFEST_DIR").unwrap());
        let target_dir = manifest_dir.join("target");
        let cache_dir = target_dir.join("vkfft-cache");
        let _ = fs::create_dir_all(&cache_dir);

        // Observation: On Windows, I'm setting both of these files generated.
        let cache_lib_unix = cache_dir.join("libvk_fft.a");
        let cache_lib_win = cache_dir.join("vk_fft.lib");

        let inputs = [
            "src/cuda/vk_fft.cu",
            "src/cuda/vk_fft.h",
            "third_party/VkFFT/vkFFT/vkFFT.h",
        ];

        let needs_rebuild = cache_is_stale(&cache_lib_unix, &cache_lib_win, &inputs);

        println!("cargo:warning=Needs build {needs_rebuild}");

        if needs_rebuild {
            // if false {
            cc::Build::new()
                .cuda(true)
                .files(["src/cuda/vk_fft.cu"])
                .define("VKFFT_BACKEND", Some("1")) //  Sets the backend to CUDA
                // .define("_CRT_SECURE_NO_WARNINGS", None)
                // .include("src/cuda")
                .include("third_party/VkFFT/vkFFT")
                .flag_if_supported("-O3")
                // .warnings(false)
                .compile("vk_fft");

            // copy from OUT_DIR to stable cache so next build is fast
            let built_unix = out_dir.join("libvk_fft.a");
            let built_win = out_dir.join("vk_fft.lib");

            if built_unix.exists() {
                let _ = fs::copy(&built_unix, &cache_lib_unix);
            }
            if built_win.exists() {
                let _ = fs::copy(&built_win, &cache_lib_win);
            }
        } else {
            // cache is good: copy FROM cache TO OUT_DIR so the linker sees it
            let dst_unix = out_dir.join("libvk_fft.a");
            let dst_win = out_dir.join("vk_fft.lib");

            if cache_lib_unix.exists() {
                let _ = fs::copy(&cache_lib_unix, &dst_unix);
            }
            if cache_lib_win.exists() {
                let _ = fs::copy(&cache_lib_win, &dst_win);
            }
        }
    }
}

/// Used to determine if we need to rebuild the vkFFT library. E.g. on a fresh git clone or
/// install from crates.io.
#[cfg(feature = "vkfft")]
fn cache_is_stale(vkfft_cache_unix: &Path, vkfft_cache_win: &Path, inputs: &[&str]) -> bool {
    let cache_path = if vkfft_cache_unix.exists() || !vkfft_cache_win.exists() {
        vkfft_cache_unix
    } else {
        vkfft_cache_win
    };

    if !vkfft_cache_unix.exists() && !vkfft_cache_win.exists() {
        return true;
    }

    let cache_meta = match fs::metadata(cache_path) {
        Ok(m) => m,
        Err(_) => return true,
    };

    let cache_time = match cache_meta.modified() {
        Ok(t) => t,
        Err(_) => return true,
    };

    for inp in inputs {
        let meta = match fs::metadata(inp) {
            Ok(m) => m,
            Err(_) => return true,
        };
        let mt = match meta.modified() {
            Ok(t) => t,
            Err(_) => return true,
        };
        if mt > cache_time {
            return true;
        }
    }

    false
}