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Optimizations of fluid simulation

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unknown 2023-07-17 16:49:35 -04:00
parent 25b74c7f93
commit 5cbb1a0ee0
2 changed files with 135 additions and 66 deletions
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3
src/main/c/compile.sh
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@ -4,6 +4,7 @@ LIB_ENDING=".so"
BASE_INCLUDE_DIR=""
OS_INCLUDE_DIR=""
#determine os
if [[ "$OSTYPE" == "linux-gnu"* ]]; then
#linux
LIB_ENDING=".so"
@ -40,7 +41,7 @@ rm -f ./*.dll
#compile object files
COMPILE_FLAGS="-c -fPIC -m64 -mavx -mavx2"
COMPILE_FLAGS="-c -fPIC -m64 -mavx -mavx2 -O1"
INPUT_FILES="./fluidsim.c"
OUTPUT_FILE="./fluidsim.o"
gcc $COMPILE_FLAGS -I"$BASE_INCLUDE_DIR" -I"$OS_INCLUDE_DIR" $INPUT_FILES -o $OUTPUT_FILE

114
src/main/c/fluidsim.c
View File

@ -6,12 +6,10 @@
#define SWAP(x0,x) {float *tmp=x0;x0=x;x=tmp;}
#define IX(i,j,k) ((i)+(N)*(j)+(N*N)*(k))
#define LINEARSOLVERTIMES 5
#define LINEARSOLVERTIMES 10
//https://docs.oracle.com/javase/1.5.0/docs/guide/jni/spec/functions.html
void diffuse(int N, int b, float * x, float * x0, float diff, float dt);
void advect(int N, int b, float * d, float * d0, float * u, float * v, float * w, float dt);
void project(int N, float * u, float * v, float * w, float * p, float * div);
@ -20,6 +18,9 @@ void dens_step(int N, float * x, float * x0, float * u, float * v, float * w, fl
void vel_step(int N, float * u, float * v, float * w, float * u0, float * v0, float * w0, float visc, float dt);
void lin_solve(int N, int b, float* x, float* x0, float a, float c);
/**
* The core simulation function
*/
JNIEXPORT void JNICALL Java_electrosphere_FluidSim_simulate(
JNIEnv * env,
jobject this,
@ -48,15 +49,13 @@ JNIEXPORT void JNICALL Java_electrosphere_FluidSim_simulate(
float * w0 = (*env)->GetDirectBufferAddress(env,jw0);
int N = DIM_X;
int i,j,k;
// for ( i=1 ; i<N-1 ; i++ ) { for ( j=1 ; j<N-1 ; j++ ) { for ( k=1 ; k<N-1 ; k++ ) {
// if(v[IX(i,j,k)] < -0.5){
// printf("%d %d %d %f \n",i,j,k,v[IX(i,j,k)]);
// }
// }}}
vel_step(DIM_X, u, v, w, u0, v0, w0, VISCOSITY_RATE, timestep);
dens_step(DIM_X, x, x0, u, v, w, DIFFUSION_RATE, timestep);
}
/**
* Adds values from a source array to a current frame array (eg more density to the main density array)
*/
void add_source(int N, float * x, float * s, float dt){
int i;
int size=N*N*N;
@ -65,19 +64,26 @@ void add_source(int N, float * x, float * s, float dt){
}
}
/**
* Diffuses a given array by a diffusion constant
*/
void diffuse(int N, int b, float * x, float * x0, float diff, float dt){
float a=dt*diff*N*N*N;
lin_solve(N, b, x, x0, a, 1+6*a);
}
/**
* Advects a given array based on the force vectors in the simulation
*/
void advect(int N, int b, float * d, float * d0, float * u, float * v, float * w, float dt){
int i, j, k, i0, j0, k0, i1, j1, k1;
float x, y, z, s0, t0, s1, t1, u1, u0, dtx,dty,dtz;
dtx=dty=dtz=dt*N;
for ( i=1 ; i<N-1 ; i++ ) { for ( j=1 ; j<N-1 ; j++ ) { for ( k=1 ; k<N-1 ; k++ ) {
for(k=1; k<N-1; k++){
for(j=1; j<N-1; j++){
for(i=1; i<N-1; i++){
x = i-dtx*u[IX(i,j,k)]; y = j-dty*v[IX(i,j,k)]; z = k-dtz*w[IX(i,j,k)];
if (x<0.5f) x=0.5f; if (x>N+0.5f) x=N+0.5f; i0=(int)x; i1=i0+1;
if (y<0.5f) y=0.5f; if (y>N+0.5f) y=N+0.5f; j0=(int)y; j1=j0+1;
@ -122,11 +128,15 @@ void advect(int N, int b, float * d, float * d0, float * u, float * v, float * w
// }
d[IX(i,j,k)] = s0*(t0*u0*d0[IX(i0,j0,k0)]+t1*u0*d0[IX(i0,j1,k0)]+t0*u1*d0[IX(i0,j0,k1)]+t1*u1*d0[IX(i0,j1,k1)])+
s1*(t0*u0*d0[IX(i1,j0,k0)]+t1*u0*d0[IX(i1,j1,k0)]+t0*u1*d0[IX(i1,j0,k1)]+t1*u1*d0[IX(i1,j1,k1)]);
}}}
}
}
}
set_bnd(N, b, d);
}
/**
* The main density step function
*/
void dens_step(int N, float * x, float * x0, float * u, float * v, float * w, float diff, float dt){
add_source(N, x, x0, dt);
SWAP(x0, x);
@ -135,6 +145,9 @@ void dens_step(int N, float * x, float * x0, float * u, float * v, float * w, fl
advect(N, 0, x, x0, u, v, w, dt);
}
/**
* The main velocity step function
*/
void vel_step(int N, float * u, float * v, float * w, float * u0, float * v0, float * w0, float visc, float dt){
add_source(N, u, u0, dt);
add_source(N, v, v0, dt);
@ -155,15 +168,68 @@ void vel_step(int N, float * u, float * v, float * w, float * u0, float * v0, fl
project(N, u, v, w, u0, v0);
}
//used for temporary vector storage when appropriate
float container[16];
/**
* Projects a given array based on force vectors
*/
void project(int N, float * u, float * v, float * w, float * p, float * div){
int i, j, k;
for ( i=1 ; i<N-1 ; i++ ) { for ( j=1 ; j<N-1 ; j++ ) { for ( k=1 ; k<N-1 ; k++ ) {
div[IX(i,j,k)] = (float)(-1.0/3.0*((u[IX(i+1,j,k)]-u[IX(i-1,j,k)])/N+(v[IX(i,j+1,k)]-v[IX(i,j-1,k)])/N+(w[IX(i,j,k+1)]-w[IX(i,j,k-1)])/N));
p[IX(i,j,k)] = 0;
}}}
__m256 nVector = _mm256_set1_ps(N);
__m256 constScalar = _mm256_set1_ps(-1.0/3.0);
__m256 zeroVec = _mm256_set1_ps(0);
__m256 vector, vector2, vector3;
for(k=1; k<N-1; k++){
for(j=1; j<N-1; j++){
i = 1;
//
//lower
//
//first part
vector = _mm256_loadu_ps(&u[IX(i+1,j,k)]);
vector = _mm256_sub_ps(vector,_mm256_loadu_ps(&u[IX(i-1,j,k)]));
vector = _mm256_div_ps(vector,nVector);
//second part
vector2 = _mm256_loadu_ps(&v[IX(i,j+1,k)]);
vector2 = _mm256_sub_ps(vector2,_mm256_loadu_ps(&v[IX(i,j-1,k)]));
vector2 = _mm256_div_ps(vector2,nVector);
//third part
vector3 = _mm256_loadu_ps(&w[IX(i,j,k+1)]);
vector3 = _mm256_sub_ps(vector3,_mm256_loadu_ps(&w[IX(i,j,k-1)]));
vector3 = _mm256_div_ps(vector3,nVector);
//multiply and finalize
vector = _mm256_add_ps(vector,_mm256_add_ps(vector2,vector3));
vector = _mm256_mul_ps(vector,constScalar);
//store
_mm256_storeu_ps(&div[IX(i,j,k)],vector);
_mm256_storeu_ps(&p[IX(i,j,k)],zeroVec);
i = 9;
//
//upper
//
//first part
vector = _mm256_loadu_ps(&u[IX(i+1,j,k)]);
vector = _mm256_sub_ps(vector,_mm256_loadu_ps(&u[IX(i-1,j,k)]));
vector = _mm256_div_ps(vector,nVector);
//second part
vector2 = _mm256_loadu_ps(&v[IX(i,j+1,k)]);
vector2 = _mm256_sub_ps(vector2,_mm256_loadu_ps(&v[IX(i,j-1,k)]));
vector2 = _mm256_div_ps(vector2,nVector);
//third part
vector3 = _mm256_loadu_ps(&w[IX(i,j,k+1)]);
vector3 = _mm256_sub_ps(vector3,_mm256_loadu_ps(&w[IX(i,j,k-1)]));
vector3 = _mm256_div_ps(vector3,nVector);
//multiply and finalize
vector = _mm256_add_ps(vector,_mm256_add_ps(vector2,vector3));
vector = _mm256_mul_ps(vector,constScalar);
//store
_mm256_storeu_ps(&div[IX(i,j,k)],vector);
_mm256_storeu_ps(&p[IX(i,j,k)],zeroVec);
}
}
set_bnd(N, 0, div);
set_bnd(N, 0, p);
@ -171,9 +237,7 @@ void project(int N, float * u, float * v, float * w, float * p, float * div){
lin_solve(N, 0, p, div, 1, 6);
__m256 constScalar = _mm256_set1_ps(0.5f*N);
__m256 vector;
__m256 vector2;
constScalar = _mm256_set1_ps(0.5f*N);
for ( k=1 ; k<N-1 ; k++ ) {
for ( j=1 ; j<N-1 ; j++ ) {
//
@ -235,11 +299,11 @@ void project(int N, float * u, float * v, float * w, float * p, float * div){
set_bnd(N, 3, w);
}
/**
* Solves a linear system of equations in a vectorized manner
*/
void lin_solve(int N, int b, float* x, float* x0, float a, float c){
int i, j, k, l, m;
__m256 aScalar = _mm256_set1_ps(a);
__m256 cScalar = _mm256_set1_ps(c);
// iterate the solver
@ -248,6 +312,7 @@ void lin_solve(int N, int b, float* x, float* x0, float a, float c){
for(k=1; k<N-1; k++){
for(j=1; j<N-1; j++){
int n = 0;
//solve as much as possible vectorized
for(i = 1; i < N-1; i=i+8){
__m256 vector = _mm256_loadu_ps(&x[IX(i-1,j,k)]);
vector = _mm256_add_ps(vector,_mm256_loadu_ps(&x[IX(i+1,j,k)]));
@ -260,6 +325,7 @@ void lin_solve(int N, int b, float* x, float* x0, float a, float c){
vector = _mm256_div_ps(vector,cScalar);
_mm256_storeu_ps(&x[IX(i,j,k)],vector);
}
//If there is any leftover, perform manual solving
if(i>N-1){
for(i=i-8; i < N-1; i++){
x[IX(i,j,k)] = (x0[IX(i,j,k)] + a*(x[IX(i-1,j,k)]+x[IX(i+1,j,k)]+x[IX(i,j-1,k)]+x[IX(i,j+1,k)]+x[IX(i,j,k-1)]+x[IX(i,j,k+1)]))/c;
@ -271,7 +337,9 @@ void lin_solve(int N, int b, float* x, float* x0, float a, float c){
}
}
/**
* Sets the bounds of the simulation
*/
void set_bnd(int N, int b, float * target){
int DIM = N;
for(int x=1; x < DIM-1; x++){