hydro_iact.h 34 KB
Newer Older
1
2
/*******************************************************************************
 * This file is part of SWIFT.
3
 * Copyright (c) 2012 Pedro Gonnet (pedro.gonnet@durham.ac.uk)
4
 *                    Matthieu Schaller (matthieu.schaller@durham.ac.uk)
5
 *
6
7
8
9
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
10
 *
11
12
13
14
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
15
 *
16
17
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
18
 *
19
 ******************************************************************************/
20
21
#ifndef SWIFT_GADGET2_HYDRO_IACT_H
#define SWIFT_GADGET2_HYDRO_IACT_H
22
23

/**
24
 * @file Gadget2/hydro_iact.h
25
26
 * @brief SPH interaction functions following the Gadget-2 version of SPH.
 *
27
 * The interactions computed here are the ones presented in the Gadget-2 paper
28
29
 * Springel, V., MNRAS, Volume 364, Issue 4, pp. 1105-1134.
 * We use the same numerical coefficients as the Gadget-2 code. When used with
30
31
32
 * the Spline-3 kernel, the results should be equivalent to the ones obtained
 * with Gadget-2 up to the rounding errors and interactions missed by the
 * Gadget-2 tree-code neighbours search.
33
34
 */

35
#include "cache.h"
James Willis's avatar
James Willis committed
36
#include "minmax.h"
37

38
39
40
/**
 * @brief Density loop
 */
41
42
43
__attribute__((always_inline)) INLINE static void runner_iact_density(
    float r2, float *dx, float hi, float hj, struct part *pi, struct part *pj) {

44
45
  float wi, wi_dx;
  float wj, wj_dx;
46
  float dv[3], curlvr[3];
47

48
  /* Get the masses. */
49
  const float mi = pi->mass;
50
51
52
53
54
55
56
57
58
59
60
61
62
  const float mj = pj->mass;

  /* Get r and r inverse. */
  const float r = sqrtf(r2);
  const float r_inv = 1.0f / r;

  /* Compute the kernel function for pi */
  const float hi_inv = 1.f / hi;
  const float ui = r * hi_inv;
  kernel_deval(ui, &wi, &wi_dx);

  /* Compute contribution to the density */
  pi->rho += mj * wi;
63
  pi->density.rho_dh -= mj * (hydro_dimension * wi + ui * wi_dx);
64

65
66
  /* Compute contribution to the number of neighbours */
  pi->density.wcount += wi;
67
  pi->density.wcount_dh -= (hydro_dimension * wi + ui * wi_dx);
68
69
70
71
72
73
74
75

  /* Compute the kernel function for pj */
  const float hj_inv = 1.f / hj;
  const float uj = r * hj_inv;
  kernel_deval(uj, &wj, &wj_dx);

  /* Compute contribution to the density */
  pj->rho += mi * wj;
76
  pj->density.rho_dh -= mi * (hydro_dimension * wj + uj * wj_dx);
77

78
79
  /* Compute contribution to the number of neighbours */
  pj->density.wcount += wj;
80
  pj->density.wcount_dh -= (hydro_dimension * wj + uj * wj_dx);
81

82
83
  const float faci = mj * wi_dx * r_inv;
  const float facj = mi * wj_dx * r_inv;
84

85
86
87
88
  /* Compute dv dot r */
  dv[0] = pi->v[0] - pj->v[0];
  dv[1] = pi->v[1] - pj->v[1];
  dv[2] = pi->v[2] - pj->v[2];
89
90
  const float dvdr = dv[0] * dx[0] + dv[1] * dx[1] + dv[2] * dx[2];

91
92
  pi->density.div_v -= faci * dvdr;
  pj->density.div_v -= facj * dvdr;
93
94
95
96
97
98

  /* Compute dv cross r */
  curlvr[0] = dv[1] * dx[2] - dv[2] * dx[1];
  curlvr[1] = dv[2] * dx[0] - dv[0] * dx[2];
  curlvr[2] = dv[0] * dx[1] - dv[1] * dx[0];

99
100
101
  pi->density.rot_v[0] += faci * curlvr[0];
  pi->density.rot_v[1] += faci * curlvr[1];
  pi->density.rot_v[2] += faci * curlvr[2];
102

103
104
105
  pj->density.rot_v[0] += facj * curlvr[0];
  pj->density.rot_v[1] += facj * curlvr[1];
  pj->density.rot_v[2] += facj * curlvr[2];
106
  
107
#ifdef DEBUG_INTERACTIONS_SPH
108
  /* Update ngb counters */
109
110
111
112
113
114
115
116
  if(pi->num_ngb_density < NUM_OF_NEIGHBOURS) {
    pi->ids_ngbs_density[pi->num_ngb_density] = pj->id;
    ++pi->num_ngb_density;
  }
  if(pj->num_ngb_density < NUM_OF_NEIGHBOURS) {
    pj->ids_ngbs_density[pj->num_ngb_density] = pi->id;
    ++pj->num_ngb_density;
  }
117
118
#endif

119
120
}

121
122
123
/**
 * @brief Density loop (non-symmetric version)
 */
124
125
126
127
128
129
130
__attribute__((always_inline)) INLINE static void runner_iact_nonsym_density(
    float r2, float *dx, float hi, float hj, struct part *pi, struct part *pj) {

  float wi, wi_dx;
  float dv[3], curlvr[3];

  /* Get the masses. */
131
  const float mj = pj->mass;
132
133

  /* Get r and r inverse. */
134
  const float r = sqrtf(r2);
135
  const float r_inv = 1.0f / r;
136

137
  /* Compute the kernel function */
138
139
140
  const float hi_inv = 1.0f / hi;
  const float ui = r * hi_inv;
  kernel_deval(ui, &wi, &wi_dx);
141
142
143

  /* Compute contribution to the density */
  pi->rho += mj * wi;
144
  pi->density.rho_dh -= mj * (hydro_dimension * wi + ui * wi_dx);
145
146
147

  /* Compute contribution to the number of neighbours */
  pi->density.wcount += wi;
148
  pi->density.wcount_dh -= (hydro_dimension * wi + ui * wi_dx);
149

150
  const float fac = mj * wi_dx * r_inv;
151

152
153
154
155
156
  /* Compute dv dot r */
  dv[0] = pi->v[0] - pj->v[0];
  dv[1] = pi->v[1] - pj->v[1];
  dv[2] = pi->v[2] - pj->v[2];
  const float dvdr = dv[0] * dx[0] + dv[1] * dx[1] + dv[2] * dx[2];
157
  pi->density.div_v -= fac * dvdr;
158

159
160
161
162
163
  /* Compute dv cross r */
  curlvr[0] = dv[1] * dx[2] - dv[2] * dx[1];
  curlvr[1] = dv[2] * dx[0] - dv[0] * dx[2];
  curlvr[2] = dv[0] * dx[1] - dv[1] * dx[0];

164
165
166
  pi->density.rot_v[0] += fac * curlvr[0];
  pi->density.rot_v[1] += fac * curlvr[1];
  pi->density.rot_v[2] += fac * curlvr[2];
167
  
168
#ifdef DEBUG_INTERACTIONS_SPH
169
  /* Update ngb counters */
170
171
172
173
  if(pi->num_ngb_density < NUM_OF_NEIGHBOURS) {
    pi->ids_ngbs_density[pi->num_ngb_density] = pj->id;
    ++pi->num_ngb_density;
  }
174
175
#endif

176
177
}

178
#ifdef WITH_VECTORIZATION
179
180
181
182
183

/**
 * @brief Density interaction computed using 1 vector
 * (non-symmetric vectorized version).
 */
184
__attribute__((always_inline)) INLINE static void
Matthieu Schaller's avatar
Matthieu Schaller committed
185
186
187
188
189
190
191
runner_iact_nonsym_1_vec_density(vector *r2, vector *dx, vector *dy, vector *dz,
                                 vector hi_inv, vector vix, vector viy,
                                 vector viz, float *Vjx, float *Vjy, float *Vjz,
                                 float *Mj, vector *rhoSum, vector *rho_dhSum,
                                 vector *wcountSum, vector *wcount_dhSum,
                                 vector *div_vSum, vector *curlvxSum,
                                 vector *curlvySum, vector *curlvzSum,
192
                                 mask_t mask) {
193

194
  vector r, ri, ui, wi, wi_dx;
195
196
197
  vector dvx, dvy, dvz;
  vector dvdr;
  vector curlvrx, curlvry, curlvrz;
James Willis's avatar
James Willis committed
198

199
  /* Fill the vectors. */
200
201
202
203
  const vector mj = vector_load(Mj);
  const vector vjx = vector_load(Vjx);
  const vector vjy = vector_load(Vjy);
  const vector vjz = vector_load(Vjz);
204
205
206
207
208

  /* Get the radius and inverse radius. */
  ri = vec_reciprocal_sqrt(*r2);
  r.v = vec_mul(r2->v, ri.v);

209
  ui.v = vec_mul(r.v, hi_inv.v);
210
211

  /* Calculate the kernel for two particles. */
212
  kernel_deval_1_vec(&ui, &wi, &wi_dx);
213
214
215
216
217
218
219
220
221
222

  /* Compute dv. */
  dvx.v = vec_sub(vix.v, vjx.v);
  dvy.v = vec_sub(viy.v, vjy.v);
  dvz.v = vec_sub(viz.v, vjz.v);

  /* Compute dv dot r */
  dvdr.v = vec_fma(dvx.v, dx->v, vec_fma(dvy.v, dy->v, vec_mul(dvz.v, dz->v)));
  dvdr.v = vec_mul(dvdr.v, ri.v);

223
224
225
226
227
228
229
230
231
232
233
  /* Compute dv cross r */
  curlvrx.v =
      vec_fma(dvy.v, dz->v, vec_mul(vec_set1(-1.0f), vec_mul(dvz.v, dy->v)));
  curlvry.v =
      vec_fma(dvz.v, dx->v, vec_mul(vec_set1(-1.0f), vec_mul(dvx.v, dz->v)));
  curlvrz.v =
      vec_fma(dvx.v, dy->v, vec_mul(vec_set1(-1.0f), vec_mul(dvy.v, dx->v)));
  curlvrx.v = vec_mul(curlvrx.v, ri.v);
  curlvry.v = vec_mul(curlvry.v, ri.v);
  curlvrz.v = vec_mul(curlvrz.v, ri.v);

234
235
  vector wcount_dh_update;
  wcount_dh_update.v =
James Willis's avatar
James Willis committed
236
      vec_fma(vec_set1(hydro_dimension), wi.v, vec_mul(ui.v, wi_dx.v));
237

238
  /* Mask updates to intermediate vector sums for particle pi. */
239
  rhoSum->v = vec_mask_add(rhoSum->v, vec_mul(mj.v, wi.v), mask);
240
241
  rho_dhSum->v =
      vec_mask_sub(rho_dhSum->v, vec_mul(mj.v, wcount_dh_update.v), mask);
242
  wcountSum->v = vec_mask_add(wcountSum->v, wi.v, mask);
243
  wcount_dhSum->v = vec_mask_sub(wcount_dhSum->v, wcount_dh_update.v, mask);
James Willis's avatar
James Willis committed
244
245
246
247
248
249
250
251
  div_vSum->v =
      vec_mask_sub(div_vSum->v, vec_mul(mj.v, vec_mul(dvdr.v, wi_dx.v)), mask);
  curlvxSum->v = vec_mask_add(curlvxSum->v,
                              vec_mul(mj.v, vec_mul(curlvrx.v, wi_dx.v)), mask);
  curlvySum->v = vec_mask_add(curlvySum->v,
                              vec_mul(mj.v, vec_mul(curlvry.v, wi_dx.v)), mask);
  curlvzSum->v = vec_mask_add(curlvzSum->v,
                              vec_mul(mj.v, vec_mul(curlvrz.v, wi_dx.v)), mask);
252
253
}

254
/**
James Willis's avatar
James Willis committed
255
256
 * @brief Density interaction computed using 2 interleaved vectors
 * (non-symmetric vectorized version).
257
258
 */
__attribute__((always_inline)) INLINE static void
James Willis's avatar
James Willis committed
259
260
261
262
263
264
265
266
runner_iact_nonsym_2_vec_density(float *R2, float *Dx, float *Dy, float *Dz,
                                 vector hi_inv, vector vix, vector viy,
                                 vector viz, float *Vjx, float *Vjy, float *Vjz,
                                 float *Mj, vector *rhoSum, vector *rho_dhSum,
                                 vector *wcountSum, vector *wcount_dhSum,
                                 vector *div_vSum, vector *curlvxSum,
                                 vector *curlvySum, vector *curlvzSum,
                                 mask_t mask, mask_t mask2, short mask_cond) {
267

268
269
  vector r, ri, ui, wi, wi_dx;
  vector dvx, dvy, dvz;
270
271
  vector dvdr;
  vector curlvrx, curlvry, curlvrz;
272
273
  vector r_2, ri2, ui2, wi2, wi_dx2;
  vector dvx2, dvy2, dvz2;
274
275
276
  vector dvdr2;
  vector curlvrx2, curlvry2, curlvrz2;

James Willis's avatar
James Willis committed
277
  /* Fill the vectors. */
278
279
280
281
282
283
284
285
286
287
288
289
290
291
  const vector mj = vector_load(Mj);
  const vector mj2 = vector_load(&Mj[VEC_SIZE]);
  const vector vjx = vector_load(Vjx);
  const vector vjx2 = vector_load(&Vjx[VEC_SIZE]);
  const vector vjy = vector_load(Vjy);
  const vector vjy2 = vector_load(&Vjy[VEC_SIZE]);
  const vector vjz = vector_load(Vjz);
  const vector vjz2 = vector_load(&Vjz[VEC_SIZE]);
  const vector dx = vector_load(Dx);
  const vector dx2 = vector_load(&Dx[VEC_SIZE]);
  const vector dy = vector_load(Dy);
  const vector dy2 = vector_load(&Dy[VEC_SIZE]);
  const vector dz = vector_load(Dz);
  const vector dz2 = vector_load(&Dz[VEC_SIZE]);
292
293

  /* Get the radius and inverse radius. */
294
295
  const vector r2 = vector_load(R2);
  const vector r2_2 = vector_load(&R2[VEC_SIZE]);
296
297
  ri = vec_reciprocal_sqrt(r2);
  ri2 = vec_reciprocal_sqrt(r2_2);
298
299
300
  r.v = vec_mul(r2.v, ri.v);
  r_2.v = vec_mul(r2_2.v, ri2.v);

301
302
  ui.v = vec_mul(r.v, hi_inv.v);
  ui2.v = vec_mul(r_2.v, hi_inv.v);
303

James Willis's avatar
James Willis committed
304
  /* Calculate the kernel for two particles. */
305
  kernel_deval_2_vec(&ui, &wi, &wi_dx, &ui2, &wi2, &wi_dx2);
306
307
308
309
310
311
312
313
314
315
316

  /* Compute dv. */
  dvx.v = vec_sub(vix.v, vjx.v);
  dvx2.v = vec_sub(vix.v, vjx2.v);
  dvy.v = vec_sub(viy.v, vjy.v);
  dvy2.v = vec_sub(viy.v, vjy2.v);
  dvz.v = vec_sub(viz.v, vjz.v);
  dvz2.v = vec_sub(viz.v, vjz2.v);

  /* Compute dv dot r */
  dvdr.v = vec_fma(dvx.v, dx.v, vec_fma(dvy.v, dy.v, vec_mul(dvz.v, dz.v)));
James Willis's avatar
James Willis committed
317
318
  dvdr2.v =
      vec_fma(dvx2.v, dx2.v, vec_fma(dvy2.v, dy2.v, vec_mul(dvz2.v, dz2.v)));
319
320
321
322
  dvdr.v = vec_mul(dvdr.v, ri.v);
  dvdr2.v = vec_mul(dvdr2.v, ri2.v);

  /* Compute dv cross r */
James Willis's avatar
James Willis committed
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
  curlvrx.v =
      vec_fma(dvy.v, dz.v, vec_mul(vec_set1(-1.0f), vec_mul(dvz.v, dy.v)));
  curlvrx2.v =
      vec_fma(dvy2.v, dz2.v, vec_mul(vec_set1(-1.0f), vec_mul(dvz2.v, dy2.v)));
  curlvry.v =
      vec_fma(dvz.v, dx.v, vec_mul(vec_set1(-1.0f), vec_mul(dvx.v, dz.v)));
  curlvry2.v =
      vec_fma(dvz2.v, dx2.v, vec_mul(vec_set1(-1.0f), vec_mul(dvx2.v, dz2.v)));
  curlvrz.v =
      vec_fma(dvx.v, dy.v, vec_mul(vec_set1(-1.0f), vec_mul(dvy.v, dx.v)));
  curlvrz2.v =
      vec_fma(dvx2.v, dy2.v, vec_mul(vec_set1(-1.0f), vec_mul(dvy2.v, dx2.v)));
  curlvrx.v = vec_mul(curlvrx.v, ri.v);
  curlvrx2.v = vec_mul(curlvrx2.v, ri2.v);
  curlvry.v = vec_mul(curlvry.v, ri.v);
  curlvry2.v = vec_mul(curlvry2.v, ri2.v);
  curlvrz.v = vec_mul(curlvrz.v, ri.v);
  curlvrz2.v = vec_mul(curlvrz2.v, ri2.v);

342
343
  vector wcount_dh_update, wcount_dh_update2;
  wcount_dh_update.v =
James Willis's avatar
James Willis committed
344
      vec_fma(vec_set1(hydro_dimension), wi.v, vec_mul(ui.v, wi_dx.v));
345
  wcount_dh_update2.v =
James Willis's avatar
James Willis committed
346
      vec_fma(vec_set1(hydro_dimension), wi2.v, vec_mul(ui2.v, wi_dx2.v));
347

James Willis's avatar
James Willis committed
348
  /* Mask updates to intermediate vector sums for particle pi. */
349
  /* Mask only when needed. */
James Willis's avatar
James Willis committed
350
  if (mask_cond) {
351
352
    rhoSum->v = vec_mask_add(rhoSum->v, vec_mul(mj.v, wi.v), mask);
    rhoSum->v = vec_mask_add(rhoSum->v, vec_mul(mj2.v, wi2.v), mask2);
James Willis's avatar
James Willis committed
353
    rho_dhSum->v =
354
        vec_mask_sub(rho_dhSum->v, vec_mul(mj.v, wcount_dh_update.v), mask);
James Willis's avatar
James Willis committed
355
    rho_dhSum->v =
356
        vec_mask_sub(rho_dhSum->v, vec_mul(mj2.v, wcount_dh_update2.v), mask2);
357
358
    wcountSum->v = vec_mask_add(wcountSum->v, wi.v, mask);
    wcountSum->v = vec_mask_add(wcountSum->v, wi2.v, mask2);
359
360
    wcount_dhSum->v = vec_mask_sub(wcount_dhSum->v, wcount_dh_update.v, mask);
    wcount_dhSum->v = vec_mask_sub(wcount_dhSum->v, wcount_dh_update2.v, mask2);
James Willis's avatar
James Willis committed
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
    div_vSum->v = vec_mask_sub(div_vSum->v,
                               vec_mul(mj.v, vec_mul(dvdr.v, wi_dx.v)), mask);
    div_vSum->v = vec_mask_sub(
        div_vSum->v, vec_mul(mj2.v, vec_mul(dvdr2.v, wi_dx2.v)), mask2);
    curlvxSum->v = vec_mask_add(
        curlvxSum->v, vec_mul(mj.v, vec_mul(curlvrx.v, wi_dx.v)), mask);
    curlvxSum->v = vec_mask_add(
        curlvxSum->v, vec_mul(mj2.v, vec_mul(curlvrx2.v, wi_dx2.v)), mask2);
    curlvySum->v = vec_mask_add(
        curlvySum->v, vec_mul(mj.v, vec_mul(curlvry.v, wi_dx.v)), mask);
    curlvySum->v = vec_mask_add(
        curlvySum->v, vec_mul(mj2.v, vec_mul(curlvry2.v, wi_dx2.v)), mask2);
    curlvzSum->v = vec_mask_add(
        curlvzSum->v, vec_mul(mj.v, vec_mul(curlvrz.v, wi_dx.v)), mask);
    curlvzSum->v = vec_mask_add(
        curlvzSum->v, vec_mul(mj2.v, vec_mul(curlvrz2.v, wi_dx2.v)), mask2);
  } else {
378
379
    rhoSum->v = vec_add(rhoSum->v, vec_mul(mj.v, wi.v));
    rhoSum->v = vec_add(rhoSum->v, vec_mul(mj2.v, wi2.v));
380
381
    rho_dhSum->v = vec_sub(rho_dhSum->v, vec_mul(mj.v, wcount_dh_update.v));
    rho_dhSum->v = vec_sub(rho_dhSum->v, vec_mul(mj2.v, wcount_dh_update2.v));
382
383
    wcountSum->v = vec_add(wcountSum->v, wi.v);
    wcountSum->v = vec_add(wcountSum->v, wi2.v);
384
385
    wcount_dhSum->v = vec_sub(wcount_dhSum->v, wcount_dh_update.v);
    wcount_dhSum->v = vec_sub(wcount_dhSum->v, wcount_dh_update2.v);
386
    div_vSum->v = vec_sub(div_vSum->v, vec_mul(mj.v, vec_mul(dvdr.v, wi_dx.v)));
James Willis's avatar
James Willis committed
387
388
389
390
391
392
393
394
395
396
397
398
399
400
    div_vSum->v =
        vec_sub(div_vSum->v, vec_mul(mj2.v, vec_mul(dvdr2.v, wi_dx2.v)));
    curlvxSum->v =
        vec_add(curlvxSum->v, vec_mul(mj.v, vec_mul(curlvrx.v, wi_dx.v)));
    curlvxSum->v =
        vec_add(curlvxSum->v, vec_mul(mj2.v, vec_mul(curlvrx2.v, wi_dx2.v)));
    curlvySum->v =
        vec_add(curlvySum->v, vec_mul(mj.v, vec_mul(curlvry.v, wi_dx.v)));
    curlvySum->v =
        vec_add(curlvySum->v, vec_mul(mj2.v, vec_mul(curlvry2.v, wi_dx2.v)));
    curlvzSum->v =
        vec_add(curlvzSum->v, vec_mul(mj.v, vec_mul(curlvrz.v, wi_dx.v)));
    curlvzSum->v =
        vec_add(curlvzSum->v, vec_mul(mj2.v, vec_mul(curlvrz2.v, wi_dx2.v)));
401
  }
402
}
James Willis's avatar
James Willis committed
403
#endif
404

405
406
407
/**
 * @brief Force loop
 */
408
409
410
__attribute__((always_inline)) INLINE static void runner_iact_force(
    float r2, float *dx, float hi, float hj, struct part *pi, struct part *pj) {

411
412
413
  float wi, wj, wi_dx, wj_dx;

  const float fac_mu = 1.f; /* Will change with cosmological integration */
414

415
416
417
418
  const float r = sqrtf(r2);
  const float r_inv = 1.0f / r;

  /* Get some values in local variables. */
419
  const float mi = pi->mass;
420
421
422
423
424
425
  const float mj = pj->mass;
  const float rhoi = pi->rho;
  const float rhoj = pj->rho;

  /* Get the kernel for hi. */
  const float hi_inv = 1.0f / hi;
426
  const float hid_inv = pow_dimension_plus_one(hi_inv); /* 1/h^(d+1) */
427
428
  const float ui = r * hi_inv;
  kernel_deval(ui, &wi, &wi_dx);
429
  const float wi_dr = hid_inv * wi_dx;
430
431
432

  /* Get the kernel for hj. */
  const float hj_inv = 1.0f / hj;
433
  const float hjd_inv = pow_dimension_plus_one(hj_inv); /* 1/h^(d+1) */
434
435
  const float xj = r * hj_inv;
  kernel_deval(xj, &wj, &wj_dx);
436
  const float wj_dr = hjd_inv * wj_dx;
437

438
439
440
441
442
  /* Compute h-gradient terms */
  const float f_i = pi->force.f;
  const float f_j = pj->force.f;

  /* Compute pressure terms */
443
444
  const float P_over_rho2_i = pi->force.P_over_rho2;
  const float P_over_rho2_j = pj->force.P_over_rho2;
445
446

  /* Compute sound speeds */
447
448
  const float ci = pi->force.soundspeed;
  const float cj = pj->force.soundspeed;
449

450
  /* Compute dv dot r. */
451
452
453
  const float dvdr = (pi->v[0] - pj->v[0]) * dx[0] +
                     (pi->v[1] - pj->v[1]) * dx[1] +
                     (pi->v[2] - pj->v[2]) * dx[2];
454

455
  /* Balsara term */
456
457
  const float balsara_i = pi->force.balsara;
  const float balsara_j = pj->force.balsara;
Matthieu Schaller's avatar
Matthieu Schaller committed
458

459
  /* Are the particles moving towards each others ? */
460
  const float omega_ij = (dvdr < 0.f) ? dvdr : 0.f;
461
462
463
464
465
466
467
468
469
  const float mu_ij = fac_mu * r_inv * omega_ij; /* This is 0 or negative */

  /* Signal velocity */
  const float v_sig = ci + cj - 3.f * mu_ij;

  /* Now construct the full viscosity term */
  const float rho_ij = 0.5f * (rhoi + rhoj);
  const float visc = -0.25f * const_viscosity_alpha * v_sig * mu_ij *
                     (balsara_i + balsara_j) / rho_ij;
470
471

  /* Now, convolve with the kernel */
472
  const float visc_term = 0.5f * visc * (wi_dr + wj_dr) * r_inv;
473
  const float sph_term =
474
      (f_i * P_over_rho2_i * wi_dr + f_j * P_over_rho2_j * wj_dr) * r_inv;
475
476
477
478
479

  /* Eventually got the acceleration */
  const float acc = visc_term + sph_term;

  /* Use the force Luke ! */
480
481
482
  pi->a_hydro[0] -= mj * acc * dx[0];
  pi->a_hydro[1] -= mj * acc * dx[1];
  pi->a_hydro[2] -= mj * acc * dx[2];
483

484
485
486
  pj->a_hydro[0] += mi * acc * dx[0];
  pj->a_hydro[1] += mi * acc * dx[1];
  pj->a_hydro[2] += mi * acc * dx[2];
487

488
  /* Get the time derivative for h. */
489
490
  pi->force.h_dt -= mj * dvdr * r_inv / rhoj * wi_dr;
  pj->force.h_dt -= mi * dvdr * r_inv / rhoi * wj_dr;
491

492
  /* Update the signal velocity. */
493
494
  pi->force.v_sig = (pi->force.v_sig > v_sig) ? pi->force.v_sig : v_sig;
  pj->force.v_sig = (pj->force.v_sig > v_sig) ? pj->force.v_sig : v_sig;
495

496
  /* Change in entropy */
497
498
  pi->entropy_dt += mj * visc_term * dvdr;
  pj->entropy_dt += mi * visc_term * dvdr;
499
  
500
#ifdef DEBUG_INTERACTIONS_SPH
501
  /* Update ngb counters */
502
503
504
505
506
507
508
509
  if(pi->num_ngb_force < NUM_OF_NEIGHBOURS) {
    pi->ids_ngbs_force[pi->num_ngb_force] = pj->id;
    ++pi->num_ngb_force;
  }
  if(pj->num_ngb_force < NUM_OF_NEIGHBOURS) {
    pj->ids_ngbs_force[pj->num_ngb_force] = pi->id;
    ++pj->num_ngb_force;
  }
510
511
#endif

512
}
513
514
515
516

/**
 * @brief Force loop (non-symmetric version)
 */
517
518
519
__attribute__((always_inline)) INLINE static void runner_iact_nonsym_force(
    float r2, float *dx, float hi, float hj, struct part *pi, struct part *pj) {

520
521
522
  float wi, wj, wi_dx, wj_dx;

  const float fac_mu = 1.f; /* Will change with cosmological integration */
523

524
525
526
527
  const float r = sqrtf(r2);
  const float r_inv = 1.0f / r;

  /* Get some values in local variables. */
528
  // const float mi = pi->mass;
529
530
531
532
533
534
  const float mj = pj->mass;
  const float rhoi = pi->rho;
  const float rhoj = pj->rho;

  /* Get the kernel for hi. */
  const float hi_inv = 1.0f / hi;
535
  const float hid_inv = pow_dimension_plus_one(hi_inv); /* 1/h^(d+1) */
536
537
  const float ui = r * hi_inv;
  kernel_deval(ui, &wi, &wi_dx);
538
  const float wi_dr = hid_inv * wi_dx;
539
540
541

  /* Get the kernel for hj. */
  const float hj_inv = 1.0f / hj;
542
  const float hjd_inv = pow_dimension_plus_one(hj_inv); /* 1/h^(d+1) */
543
544
  const float xj = r * hj_inv;
  kernel_deval(xj, &wj, &wj_dx);
545
  const float wj_dr = hjd_inv * wj_dx;
546

547
548
549
550
551
  /* Compute h-gradient terms */
  const float f_i = pi->force.f;
  const float f_j = pj->force.f;

  /* Compute pressure terms */
552
553
  const float P_over_rho2_i = pi->force.P_over_rho2;
  const float P_over_rho2_j = pj->force.P_over_rho2;
554
555

  /* Compute sound speeds */
556
557
  const float ci = pi->force.soundspeed;
  const float cj = pj->force.soundspeed;
558

559
  /* Compute dv dot r. */
560
561
562
  const float dvdr = (pi->v[0] - pj->v[0]) * dx[0] +
                     (pi->v[1] - pj->v[1]) * dx[1] +
                     (pi->v[2] - pj->v[2]) * dx[2];
563

564
  /* Balsara term */
565
566
  const float balsara_i = pi->force.balsara;
  const float balsara_j = pj->force.balsara;
567
568

  /* Are the particles moving towards each others ? */
569
  const float omega_ij = (dvdr < 0.f) ? dvdr : 0.f;
570
571
572
573
574
575
576
577
578
  const float mu_ij = fac_mu * r_inv * omega_ij; /* This is 0 or negative */

  /* Signal velocity */
  const float v_sig = ci + cj - 3.f * mu_ij;

  /* Now construct the full viscosity term */
  const float rho_ij = 0.5f * (rhoi + rhoj);
  const float visc = -0.25f * const_viscosity_alpha * v_sig * mu_ij *
                     (balsara_i + balsara_j) / rho_ij;
579
580

  /* Now, convolve with the kernel */
581
  const float visc_term = 0.5f * visc * (wi_dr + wj_dr) * r_inv;
582
  const float sph_term =
583
      (f_i * P_over_rho2_i * wi_dr + f_j * P_over_rho2_j * wj_dr) * r_inv;
584
585
586

  /* Eventually got the acceleration */
  const float acc = visc_term + sph_term;
587

588
  /* Use the force Luke ! */
589
590
591
  pi->a_hydro[0] -= mj * acc * dx[0];
  pi->a_hydro[1] -= mj * acc * dx[1];
  pi->a_hydro[2] -= mj * acc * dx[2];
592

593
  /* Get the time derivative for h. */
594
  pi->force.h_dt -= mj * dvdr * r_inv / rhoj * wi_dr;
595

596
  /* Update the signal velocity. */
597
  pi->force.v_sig = (pi->force.v_sig > v_sig) ? pi->force.v_sig : v_sig;
598

599
  /* Change in entropy */
600
  pi->entropy_dt += mj * visc_term * dvdr;
601
  
602
#ifdef DEBUG_INTERACTIONS_SPH
603
  /* Update ngb counters */
604
605
606
607
  if(pi->num_ngb_force < NUM_OF_NEIGHBOURS) {
    pi->ids_ngbs_force[pi->num_ngb_force] = pj->id;
    ++pi->num_ngb_force;
  }
608
609
#endif

610
}
611

612
#ifdef WITH_VECTORIZATION
James Willis's avatar
James Willis committed
613
614
static const vector const_viscosity_alpha_fac =
    FILL_VEC(-0.25f * const_viscosity_alpha);
615

James Willis's avatar
James Willis committed
616
617
618
619
/**
 * @brief Force interaction computed using 1 vector
 * (non-symmetric vectorized version).
 */
James Willis's avatar
James Willis committed
620
621
__attribute__((always_inline)) INLINE static void
runner_iact_nonsym_1_vec_force(
622
    vector *r2, vector *dx, vector *dy, vector *dz, vector vix, vector viy,
James Willis's avatar
James Willis committed
623
624
625
    vector viz, vector pirho, vector grad_hi, vector piPOrho2, vector balsara_i,
    vector ci, float *Vjx, float *Vjy, float *Vjz, float *Pjrho, float *Grad_hj,
    float *PjPOrho2, float *Balsara_j, float *Cj, float *Mj, vector hi_inv,
626
    vector hj_inv, vector *a_hydro_xSum, vector *a_hydro_ySum,
James Willis's avatar
James Willis committed
627
628
    vector *a_hydro_zSum, vector *h_dtSum, vector *v_sigSum,
    vector *entropy_dtSum, mask_t mask) {
629
630
631

#ifdef WITH_VECTORIZATION

632
  vector r, ri;
633
  vector dvx, dvy, dvz;
634
635
  vector xi, xj;
  vector hid_inv, hjd_inv;
636
  vector wi_dx, wj_dx, wi_dr, wj_dr, dvdr;
637
638
639
  vector piax, piay, piaz;
  vector pih_dt;
  vector v_sig;
640
  vector omega_ij, mu_ij, balsara;
641
642
643
  vector rho_ij, visc, visc_term, sph_term, acc, entropy_dt;

  /* Fill vectors. */
644
645
646
647
648
649
650
651
652
  const vector vjx = vector_load(Vjx);
  const vector vjy = vector_load(Vjy);
  const vector vjz = vector_load(Vjz);
  const vector mj = vector_load(Mj);
  const vector pjrho = vector_load(Pjrho);
  const vector grad_hj = vector_load(Grad_hj);
  const vector pjPOrho2 = vector_load(PjPOrho2);
  const vector balsara_j = vector_load(Balsara_j);
  const vector cj = vector_load(Cj);
653

654
655
  const vector fac_mu =
      vector_set1(1.f); /* Will change with cosmological integration */
656

James Willis's avatar
James Willis committed
657
  /* Load stuff. */
658
  balsara.v = vec_add(balsara_i.v, balsara_j.v);
659
660

  /* Get the radius and inverse radius. */
661
  ri = vec_reciprocal_sqrt(*r2);
662
  r.v = vec_mul(r2->v, ri.v);
663
664

  /* Get the kernel for hi. */
665
  hid_inv = pow_dimension_plus_one_vec(hi_inv);
666
  xi.v = vec_mul(r.v, hi_inv.v);
667
  kernel_eval_dWdx_force_vec(&xi, &wi_dx);
668
  wi_dr.v = vec_mul(hid_inv.v, wi_dx.v);
669
670
671

  /* Get the kernel for hj. */
  hjd_inv = pow_dimension_plus_one_vec(hj_inv);
672
  xj.v = vec_mul(r.v, hj_inv.v);
James Willis's avatar
James Willis committed
673

674
  /* Calculate the kernel. */
James Willis's avatar
James Willis committed
675
  kernel_eval_dWdx_force_vec(&xj, &wj_dx);
James Willis's avatar
James Willis committed
676

677
678
679
680
681
682
  wj_dr.v = vec_mul(hjd_inv.v, wj_dx.v);

  /* Compute dv. */
  dvx.v = vec_sub(vix.v, vjx.v);
  dvy.v = vec_sub(viy.v, vjy.v);
  dvz.v = vec_sub(viz.v, vjz.v);
683
684

  /* Compute dv dot r. */
685
  dvdr.v = vec_fma(dvx.v, dx->v, vec_fma(dvy.v, dy->v, vec_mul(dvz.v, dz->v)));
686
687
688

  /* Compute the relative velocity. (This is 0 if the particles move away from
   * each other and negative otherwise) */
689
  omega_ij.v = vec_fmin(dvdr.v, vec_setzero());
James Willis's avatar
James Willis committed
690
691
  mu_ij.v =
      vec_mul(fac_mu.v, vec_mul(ri.v, omega_ij.v)); /* This is 0 or negative */
692
693

  /* Compute signal velocity */
694
  v_sig.v = vec_fnma(vec_set1(3.f), mu_ij.v, vec_add(ci.v, cj.v));
695
696

  /* Now construct the full viscosity term */
697
  rho_ij.v = vec_mul(vec_set1(0.5f), vec_add(pirho.v, pjrho.v));
James Willis's avatar
James Willis committed
698
699
700
  visc.v = vec_div(vec_mul(const_viscosity_alpha_fac.v,
                           vec_mul(v_sig.v, vec_mul(mu_ij.v, balsara.v))),
                   rho_ij.v);
701
702

  /* Now, convolve with the kernel */
James Willis's avatar
James Willis committed
703
704
705
  visc_term.v =
      vec_mul(vec_set1(0.5f),
              vec_mul(visc.v, vec_mul(vec_add(wi_dr.v, wj_dr.v), ri.v)));
James Willis's avatar
James Willis committed
706

707
  sph_term.v =
James Willis's avatar
James Willis committed
708
709
710
      vec_mul(vec_fma(vec_mul(grad_hi.v, piPOrho2.v), wi_dr.v,
                      vec_mul(grad_hj.v, vec_mul(pjPOrho2.v, wj_dr.v))),
              ri.v);
James Willis's avatar
James Willis committed
711

712
  /* Eventually get the acceleration */
713
  acc.v = vec_add(visc_term.v, sph_term.v);
714
715

  /* Use the force, Luke! */
716
717
718
  piax.v = vec_mul(mj.v, vec_mul(dx->v, acc.v));
  piay.v = vec_mul(mj.v, vec_mul(dy->v, acc.v));
  piaz.v = vec_mul(mj.v, vec_mul(dz->v, acc.v));
719
720

  /* Get the time derivative for h. */
James Willis's avatar
James Willis committed
721
722
  pih_dt.v =
      vec_div(vec_mul(mj.v, vec_mul(dvdr.v, vec_mul(ri.v, wi_dr.v))), pjrho.v);
723
724

  /* Change in entropy */
725
  entropy_dt.v = vec_mul(mj.v, vec_mul(visc_term.v, dvdr.v));
726

727
  /* Store the forces back on the particles. */
728
729
730
731
  a_hydro_xSum->v = vec_mask_sub(a_hydro_xSum->v, piax.v, mask);
  a_hydro_ySum->v = vec_mask_sub(a_hydro_ySum->v, piay.v, mask);
  a_hydro_zSum->v = vec_mask_sub(a_hydro_zSum->v, piaz.v, mask);
  h_dtSum->v = vec_mask_sub(h_dtSum->v, pih_dt.v, mask);
732
  v_sigSum->v = vec_fmax(v_sigSum->v, vec_and_mask(v_sig.v, mask));
733
  entropy_dtSum->v = vec_mask_add(entropy_dtSum->v, entropy_dt.v, mask);
734
735
736
737
738
739
740
741
742
743

#else

  error(
      "The Gadget2 serial version of runner_iact_nonsym_force was called when "
      "the vectorised version should have been used.");

#endif
}

James Willis's avatar
James Willis committed
744
745
746
747
/**
 * @brief Force interaction computed using 2 interleaved vectors
 * (non-symmetric vectorized version).
 */
James Willis's avatar
James Willis committed
748
749
__attribute__((always_inline)) INLINE static void
runner_iact_nonsym_2_vec_force(
750
    float *R2, float *Dx, float *Dy, float *Dz, vector vix, vector viy,
James Willis's avatar
James Willis committed
751
752
753
754
755
756
    vector viz, vector pirho, vector grad_hi, vector piPOrho2, vector balsara_i,
    vector ci, float *Vjx, float *Vjy, float *Vjz, float *Pjrho, float *Grad_hj,
    float *PjPOrho2, float *Balsara_j, float *Cj, float *Mj, vector hi_inv,
    float *Hj_inv, vector *a_hydro_xSum, vector *a_hydro_ySum,
    vector *a_hydro_zSum, vector *h_dtSum, vector *v_sigSum,
    vector *entropy_dtSum, mask_t mask, mask_t mask_2, short mask_cond) {
757
758
759

#ifdef WITH_VECTORIZATION

760
761
  vector r, ri;
  vector dvx, dvy, dvz;
762
  vector ui, uj;
763
  vector hid_inv, hjd_inv;
764
  vector wi_dx, wj_dx, wi_dr, wj_dr, dvdr;
765
766
767
  vector piax, piay, piaz;
  vector pih_dt;
  vector v_sig;
768
  vector omega_ij, mu_ij, balsara;
769
770
  vector rho_ij, visc, visc_term, sph_term, acc, entropy_dt;

771
772
  vector r_2, ri_2;
  vector dvx_2, dvy_2, dvz_2;
773
  vector ui_2, uj_2;
774
  vector hjd_inv_2;
775
  vector wi_dx_2, wj_dx_2, wi_dr_2, wj_dr_2, dvdr_2;
776
777
778
779
780
781
782
  vector piax_2, piay_2, piaz_2;
  vector pih_dt_2;
  vector v_sig_2;
  vector omega_ij_2, mu_ij_2, balsara_2;
  vector rho_ij_2, visc_2, visc_term_2, sph_term_2, acc_2, entropy_dt_2;

  /* Fill vectors. */
783
784
785
786
787
788
789
790
791
792
793
794
795
796
  const vector mj = vector_load(Mj);
  const vector mj_2 = vector_load(&Mj[VEC_SIZE]);
  const vector vjx = vector_load(Vjx);
  const vector vjx_2 = vector_load(&Vjx[VEC_SIZE]);
  const vector vjy = vector_load(Vjy);
  const vector vjy_2 = vector_load(&Vjy[VEC_SIZE]);
  const vector vjz = vector_load(Vjz);
  const vector vjz_2 = vector_load(&Vjz[VEC_SIZE]);
  const vector dx = vector_load(Dx);
  const vector dx_2 = vector_load(&Dx[VEC_SIZE]);
  const vector dy = vector_load(Dy);
  const vector dy_2 = vector_load(&Dy[VEC_SIZE]);
  const vector dz = vector_load(Dz);
  const vector dz_2 = vector_load(&Dz[VEC_SIZE]);
James Willis's avatar
James Willis committed
797

798
  /* Get the radius and inverse radius. */
799
800
  const vector r2 = vector_load(R2);
  const vector r2_2 = vector_load(&R2[VEC_SIZE]);
801
802
803
804
  ri = vec_reciprocal_sqrt(r2);
  ri_2 = vec_reciprocal_sqrt(r2_2);
  r.v = vec_mul(r2.v, ri.v);
  r_2.v = vec_mul(r2_2.v, ri_2.v);
805

806
  /* Get remaining properties. */
807
808
809
810
811
812
813
814
815
816
817
818
  const vector pjrho = vector_load(Pjrho);
  const vector pjrho_2 = vector_load(&Pjrho[VEC_SIZE]);
  const vector grad_hj = vector_load(Grad_hj);
  const vector grad_hj_2 = vector_load(&Grad_hj[VEC_SIZE]);
  const vector pjPOrho2 = vector_load(PjPOrho2);
  const vector pjPOrho2_2 = vector_load(&PjPOrho2[VEC_SIZE]);
  const vector balsara_j = vector_load(Balsara_j);
  const vector balsara_j_2 = vector_load(&Balsara_j[VEC_SIZE]);
  const vector cj = vector_load(Cj);
  const vector cj_2 = vector_load(&Cj[VEC_SIZE]);
  const vector hj_inv = vector_load(Hj_inv);
  const vector hj_inv_2 = vector_load(&Hj_inv[VEC_SIZE]);
819

820
821
  const vector fac_mu =
      vector_set1(1.f); /* Will change with cosmological integration */
822

823
824
825
  /* Find the balsara switch. */
  balsara.v = vec_add(balsara_i.v, balsara_j.v);
  balsara_2.v = vec_add(balsara_i.v, balsara_j_2.v);
826
827

  /* Get the kernel for hi. */
828
  hid_inv = pow_dimension_plus_one_vec(hi_inv);
829
830
831
832
833
834
  ui.v = vec_mul(r.v, hi_inv.v);
  ui_2.v = vec_mul(r_2.v, hi_inv.v);
  kernel_eval_dWdx_force_vec(&ui, &wi_dx);
  kernel_eval_dWdx_force_vec(&ui_2, &wi_dx_2);
  wi_dr.v = vec_mul(hid_inv.v, wi_dx.v);
  wi_dr_2.v = vec_mul(hid_inv.v, wi_dx_2.v);
835
836
837
838

  /* Get the kernel for hj. */
  hjd_inv = pow_dimension_plus_one_vec(hj_inv);
  hjd_inv_2 = pow_dimension_plus_one_vec(hj_inv_2);
839
840
  uj.v = vec_mul(r.v, hj_inv.v);
  uj_2.v = vec_mul(r_2.v, hj_inv_2.v);
James Willis's avatar
James Willis committed
841

842
  /* Calculate the kernel for two particles. */
843
844
  kernel_eval_dWdx_force_vec(&uj, &wj_dx);
  kernel_eval_dWdx_force_vec(&uj_2, &wj_dx_2);
James Willis's avatar
James Willis committed
845

846
847
  wj_dr.v = vec_mul(hjd_inv.v, wj_dx.v);
  wj_dr_2.v = vec_mul(hjd_inv_2.v, wj_dx_2.v);
848

849
850
851
852
853
854
855
  /* Compute dv. */
  dvx.v = vec_sub(vix.v, vjx.v);
  dvx_2.v = vec_sub(vix.v, vjx_2.v);
  dvy.v = vec_sub(viy.v, vjy.v);
  dvy_2.v = vec_sub(viy.v, vjy_2.v);
  dvz.v = vec_sub(viz.v, vjz.v);
  dvz_2.v = vec_sub(viz.v, vjz_2.v);
856
857

  /* Compute dv dot r. */
858
  dvdr.v = vec_fma(dvx.v, dx.v, vec_fma(dvy.v, dy.v, vec_mul(dvz.v, dz.v)));
James Willis's avatar
James Willis committed
859
860
  dvdr_2.v = vec_fma(dvx_2.v, dx_2.v,
                     vec_fma(dvy_2.v, dy_2.v, vec_mul(dvz_2.v, dz_2.v)));
861
862
863
864
865

  /* Compute the relative velocity. (This is 0 if the particles move away from
   * each other and negative otherwise) */
  omega_ij.v = vec_fmin(dvdr.v, vec_setzero());
  omega_ij_2.v = vec_fmin(dvdr_2.v, vec_setzero());
James Willis's avatar
James Willis committed
866
867
868
869
  mu_ij.v =
      vec_mul(fac_mu.v, vec_mul(ri.v, omega_ij.v)); /* This is 0 or negative */
  mu_ij_2.v = vec_mul(
      fac_mu.v, vec_mul(ri_2.v, omega_ij_2.v)); /* This is 0 or negative */
870
871

  /* Compute signal velocity */
872
873
  v_sig.v = vec_fnma(vec_set1(3.f), mu_ij.v, vec_add(ci.v, cj.v));
  v_sig_2.v = vec_fnma(vec_set1(3.f), mu_ij_2.v, vec_add(ci.v, cj_2.v));
874
875

  /* Now construct the full viscosity term */
876
877
878
  rho_ij.v = vec_mul(vec_set1(0.5f), vec_add(pirho.v, pjrho.v));
  rho_ij_2.v = vec_mul(vec_set1(0.5f), vec_add(pirho.v, pjrho_2.v));

James Willis's avatar
James Willis committed
879
880
881
882
883
884
885
  visc.v = vec_div(vec_mul(const_viscosity_alpha_fac.v,
                           vec_mul(v_sig.v, vec_mul(mu_ij.v, balsara.v))),
                   rho_ij.v);
  visc_2.v =
      vec_div(vec_mul(const_viscosity_alpha_fac.v,
                      vec_mul(v_sig_2.v, vec_mul(mu_ij_2.v, balsara_2.v))),
              rho_ij_2.v);
886
887

  /* Now, convolve with the kernel */
James Willis's avatar
James Willis committed
888
889
890
891
892
893
894
  visc_term.v =
      vec_mul(vec_set1(0.5f),
              vec_mul(visc.v, vec_mul(vec_add(wi_dr.v, wj_dr.v), ri.v)));
  visc_term_2.v = vec_mul(
      vec_set1(0.5f),
      vec_mul(visc_2.v, vec_mul(vec_add(wi_dr_2.v, wj_dr_2.v), ri_2.v)));

895
896
897
  vector grad_hi_mul_piPOrho2;
  grad_hi_mul_piPOrho2.v = vec_mul(grad_hi.v, piPOrho2.v);

898
  sph_term.v =
James Willis's avatar
James Willis committed
899
900
901
902
903
904
905
      vec_mul(vec_fma(grad_hi_mul_piPOrho2.v, wi_dr.v,
                      vec_mul(grad_hj.v, vec_mul(pjPOrho2.v, wj_dr.v))),
              ri.v);
  sph_term_2.v =
      vec_mul(vec_fma(grad_hi_mul_piPOrho2.v, wi_dr_2.v,
                      vec_mul(grad_hj_2.v, vec_mul(pjPOrho2_2.v, wj_dr_2.v))),
              ri_2.v);
906
907

  /* Eventually get the acceleration */
908
909
  acc.v = vec_add(visc_term.v, sph_term.v);
  acc_2.v = vec_add(visc_term_2.v, sph_term_2.v);
910
911

  /* Use the force, Luke! */
912
913
914
915
916
917
  piax.v = vec_mul(mj.v, vec_mul(dx.v, acc.v));
  piax_2.v = vec_mul(mj_2.v, vec_mul(dx_2.v, acc_2.v));
  piay.v = vec_mul(mj.v, vec_mul(dy.v, acc.v));
  piay_2.v = vec_mul(mj_2.v, vec_mul(dy_2.v, acc_2.v));
  piaz.v = vec_mul(mj.v, vec_mul(dz.v, acc.v));
  piaz_2.v = vec_mul(mj_2.v, vec_mul(dz_2.v, acc_2.v));
918
919

  /* Get the time derivative for h. */
James Willis's avatar
James Willis committed
920
921
922
923
924
  pih_dt.v =
      vec_div(vec_mul(mj.v, vec_mul(dvdr.v, vec_mul(ri.v, wi_dr.v))), pjrho.v);
  pih_dt_2.v =
      vec_div(vec_mul(mj_2.v, vec_mul(dvdr_2.v, vec_mul