oxiphysics_gpu/kernels/md_force/
ewaldrealspacekernel_traits.rs

1//! # EwaldRealSpaceKernel - Trait Implementations
2//!
3//! This module contains trait implementations for `EwaldRealSpaceKernel`.
4//!
5//! ## Implemented Traits
6//!
7//! - `ComputeKernel`
8//!
9//! 🤖 Generated with [SplitRS](https://github.com/cool-japan/splitrs)
10
11use crate::compute::ComputeKernel;
12
13use super::functions::erfc_approx;
14use super::types::EwaldRealSpaceKernel;
15
16impl ComputeKernel for EwaldRealSpaceKernel {
17    fn name(&self) -> &str {
18        "EwaldRealSpaceKernel"
19    }
20    fn execute(&self, inputs: &[&[f64]], outputs: &mut [Vec<f64>], work_size: usize) {
21        if inputs.len() < 3 || outputs.len() < 2 {
22            return;
23        }
24        let pos = inputs[0];
25        let charges = inputs[1];
26        let alpha = inputs[2][0];
27        let r_cutoff = inputs[2][1];
28        let box_len = inputs[2][2];
29        let n = work_size;
30        let r_cut2 = r_cutoff * r_cutoff;
31        let half_box = box_len * 0.5;
32        let mut forces = vec![0.0f64; n * 3];
33        let mut energy = 0.0f64;
34        for i in 0..n {
35            let xi = [pos[i * 3], pos[i * 3 + 1], pos[i * 3 + 2]];
36            let qi = charges[i];
37            for j in (i + 1)..n {
38                let xj = [pos[j * 3], pos[j * 3 + 1], pos[j * 3 + 2]];
39                let qj = charges[j];
40                let mut dx = xi[0] - xj[0];
41                let mut dy = xi[1] - xj[1];
42                let mut dz = xi[2] - xj[2];
43                if dx > half_box {
44                    dx -= box_len;
45                } else if dx < -half_box {
46                    dx += box_len;
47                }
48                if dy > half_box {
49                    dy -= box_len;
50                } else if dy < -half_box {
51                    dy += box_len;
52                }
53                if dz > half_box {
54                    dz -= box_len;
55                } else if dz < -half_box {
56                    dz += box_len;
57                }
58                let r2 = dx * dx + dy * dy + dz * dz;
59                if r2 >= r_cut2 || r2 < 1e-30 {
60                    continue;
61                }
62                let r = r2.sqrt();
63                let ar = alpha * r;
64                let erfc_ar = erfc_approx(ar);
65                energy += qi * qj * erfc_ar / r;
66                let two_alpha_over_sqrt_pi = 2.0 * alpha / std::f64::consts::PI.sqrt();
67                let deriv = -(erfc_ar / r + two_alpha_over_sqrt_pi * (-ar * ar).exp()) / r;
68                let f_mag = -qi * qj * deriv / r;
69                forces[i * 3] += f_mag * dx;
70                forces[i * 3 + 1] += f_mag * dy;
71                forces[i * 3 + 2] += f_mag * dz;
72                forces[j * 3] -= f_mag * dx;
73                forces[j * 3 + 1] -= f_mag * dy;
74                forces[j * 3 + 2] -= f_mag * dz;
75            }
76        }
77        outputs[0] = forces;
78        outputs[1] = vec![energy];
79    }
80}
oxiphysics_gpu/kernels/md_force/ewaldrealspacekernel_traits.rs

oxiphysics_gpu/kernels/md_force/
ewaldrealspacekernel_traits.rs
