#include <mpi.h>
#include <cl.h>
#include <malloc.h>
// kernel
#define BLOCK (512)
const char *source =
"__kernel void sub1(__global float* fx,\
__global const float* fy,\
__local float* se, __global float* fe) {\
const unsigned int t = get_global_id(0);\
const unsigned int b = get_group_id(0);\
const unsigned block = 512;\
const unsigned int i = block*b+t;\
float e;\
/* do computation */\
fx[t] += ( fy[t+2] + fy[t] )*.5;\
e = fy[t+1] * fy[t+1];\
/* reduction */\
se[t] = e;\
barrier(CLK_LOCAL_MEM_FENCE);\
if (t<256) {\
se[t] += se[t+256];\
barrier(CLK_LOCAL_MEM_FENCE);\
}\
if (t<128) {\
se[t] += se[t+128];\
barrier(CLK_LOCAL_MEM_FENCE);\
}\
if (t<64) {\
se[t] += se[t+64];\
barrier(CLK_LOCAL_MEM_FENCE);\
}\
if (t<32) {\
se[t] += se[t+32];\
se[t] += se[t+16];\
se[t] += se[t+8];\
se[t] += se[t+4];\
se[t] += se[t+2];\
se[t] += se[t+1];\
}\
if (t==0)\
fe[b] = se[0];\
}";
int main(int argc, char *argv[]) {
int n = ...;
MPI_Init(&argc, &argv);
int numproc, me;
MPI_Comm_size(MPI_COMM_WORLD, &numproc);
MPI_Comm_rank(MPI_COMM_WORLD, &me);
int p_left = -1, p_right = -1;
if (me > 0)
p_left = me-1;
if (me < numproc-1)
p_right = me+1;
int n_local0 = 1 + (me * (n-1)) / numproc;
int n_local1 = 1 + ((me+1) * (n-1)) / numproc;
// allocate only local part + ghost zone of the arrays x,y
float *x, *y;
MPI_Alloc_mem(sizeof(float) * (n_local1 - n_local0 + 2),
MPI_INFO_NULL, &x);
MPI_Alloc_mem(sizeof(float) * (n_local1 - n_local0 + 2),
MPI_INFO_NULL, &y);
x -= (n_local0 - 1);
y -= (n_local0 - 1);
MPI_Win win;
MPI_Win_create(&y[n_local0], sizeof(float) * (n_local1-n_local0+2),
sizeof(float), MPI_INFO_NULL, MPI_COMM_WORLD, &win);
... // fill x, y
// fill ghost zone
MPI_Win_fence(0, win);
if (p_left != -1)
MPI_Put(&y[n_local0], 1, MPI_FLOAT, p_left,
n_local1-n_local0+1, 1, MPI_FLOAT, win);
if (p_right != -1)
MPI_Put(&y[n_local1-1], 1, MPI_FLOAT, p_right,
0, 1, MPI_FLOAT, win);
MPI_Win_fence(0, win);
// allocate GPU
cl_context ct = clCreateContextFromType(0, CL_DEVICE_TYPE_GPU, 0, 0, 0);
size_t ctsize;
clGetContextInfo(ct, CL_CONTEXT_DEVICES, 0, 0, &ctsize);
cl_device_id *aDevices = (cl_device_id*)malloc(ctsize);
clGetContextInfo(ct, CL_CONTEXT_DEVICES, ctsize, aDevices, 0);
// compile kernel
cl_program prog = clCreateProgramWithSource(ct, 1, &source, 0, 0);
clBuildProgram(prog, 0, 0, 0, 0, 0);
cl_kernel kern = clCreateKernel(prog, "sub1", 0);
float e = 0;
cl_command_queue queue = clCreateCommandQueue(ct, aDevices[0], 0, 0);
// allocate GPU memory
cl_mem fx = clCreateBuffer(ct, CL_MEM_READ_WRITE | CL_MEM_COPY_HOST_PTR,
(n_local1-n_local0)*sizeof(cl_float), &x[n_local0], 0);
cl_mem fy = clCreateBuffer(ct, CL_MEM_READ_ONLY | CL_MEM_COPY_HOST_PTR,
(n_local1-n_local0+2)*sizeof(cl_float), &y[n_local0-1], 0);
cl_mem se = clCreateBuffer(ct, CL_MEM_READ_WRITE,
BLOCK*sizeof(cl_float), 0, 0);
cl_mem fe = clCreateBuffer(ct, CL_MEM_WRITE_ONLY,
(n_local1-n_local0)/BLOCK*sizeof(cl_float), 0, 0);
clSetKernelArg(kern, 0, sizeof(cl_mem), (void *)&fx);
clSetKernelArg(kern, 1, sizeof(cl_mem), (void *)&fx);
clSetKernelArg(kern, 2, sizeof(cl_mem), (void *)&se);
clSetKernelArg(kern, 3, sizeof(cl_mem), (void *)&fe);
float *d = new float[(n_local1-n_local0)/BLOCK];
// call GPU
const unsigned int size = BLOCK;
const unsigned int dim = n_local1-n_local0+2;
clEnqueueNDRangeKernel(queue, kern, 1, 0, &dim, &size, 0, 0, 0);
// copy to host memory
clEnqueueReadBuffer(queue, fx, CL_TRUE, 0,
(n_local1-n_local0) * sizeof(cl_float), &x[n_local0], 0, 0, 0);
clEnqueueReadBuffer(queue, fe, CL_TRUE, 0,
(n_local1-n_local0) * sizeof(cl_float), d, 0, 0, 0);
float ee = 0;
for (int i=0; i<(n_local1-n_local0)/BLOCK; ++i)
ee += d[i];
e += ee;
delete[] d;
// release GPU memory
clReleaseMemObject(fx);
clReleaseMemObject(fy);
clReleaseMemObject(se);
clReleaseMemObject(fe);
float e_local = e;
MPI_Allreduce(&e_local, &e, 1, MPI_FLOAT, MPI_SUM, MPI_COMM_WORLD);
... // output x, e
MPI_Win_free(&win);
x += (n_local0 - 1);
y += (n_local0 - 1);
MPI_Free_mem(y);
MPI_Free_mem(x);
MPI_Finalize();
return 0;
}
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