import pyopencl as cl
mf = cl.mem_flags

import numpy
import time

import matplotlib
import matplotlib.pyplot as plt
matplotlib.use('AGG')

import sympy
import lbm_d2q9 as D2Q9

from mako.template import Template

kernel = """
__constant float tau = ${tau};

bool is_in_circle(float x, float y, float a, float b, float r) {
    return sqrt(pow(x-a,2)+pow(y-b,2)) < r;
}

__kernel void equilibrilize(__global __write_only float* f_a,
                            __global __write_only float* f_b)
{
    const unsigned int gid = get_global_id(1)*${nX} + get_global_id(0);

    __global __write_only float* preshifted_f_a = f_a + gid;
    __global __write_only float* preshifted_f_b = f_b + gid;

    if (  is_in_circle(get_global_id(0), get_global_id(1), ${nX//4},    ${nY//4},    ${nX//10})
       || is_in_circle(get_global_id(0), get_global_id(1), ${nX//4},    ${nY-nY//4}, ${nX//10})
       || is_in_circle(get_global_id(0), get_global_id(1), ${nX-nX//4}, ${nY//4},    ${nX//10})
       || is_in_circle(get_global_id(0), get_global_id(1), ${nX-nX//4}, ${nY-nY//4}, ${nX//10}) ) {
% for i, w_i in enumerate(w):
        preshifted_f_a[${i*nCells}] = 1./24.f;
        preshifted_f_b[${i*nCells}] = 1./24.f;
% endfor
    } else {
% for i, w_i in enumerate(w):
        preshifted_f_a[${i*nCells}] = ${w_i}.f;
        preshifted_f_b[${i*nCells}] = ${w_i}.f;
% endfor
    }
}

<%
def direction_index(c_i):
    return (c_i[0]+1) + 3*(1-c_i[1])

def neighbor_offset(c_i):
    if c_i[1] == 0:
        return c_i[0]
    else:
        return c_i[1]*nX + c_i[0]
%>

__kernel void collide_and_stream(__global __write_only float* f_a,
                                 __global __read_only  float* f_b,
                                 __global __read_only  int* material)
{
    const unsigned int gid = get_global_id(1)*${nX} + get_global_id(0);

    const int m = material[gid];

    if ( m == 0 ) {
        return;
    }

    __global __write_only float* preshifted_f_a = f_a + gid;
    __global __read_only  float* preshifted_f_b = f_b + gid;

% for i, c_i in enumerate(c):
    const float f_curr_${i} = preshifted_f_b[${direction_index(c_i)*nCells + neighbor_offset(-c_i)}];
% endfor

% for i, expr in enumerate(moments_helper):
    const float ${expr[0]} = ${ccode(expr[1])};
% endfor

% for i, expr in enumerate(moments_assignment):
    float ${ccode(expr)}
% endfor

    if ( m == 2 ) {
        u_0 = 0.0;
        u_1 = 0.0;
    }

% for i, expr in enumerate(collide_helper):
    const float ${expr[0]} = ${ccode(expr[1])};
% endfor

% for i, expr in enumerate(collide_assignment):
    const float ${ccode(expr)}
% endfor

% for i in range(0,len(c)):
    preshifted_f_a[${i*nCells}] = f_next_${i};
% endfor
}

__kernel void collect_moments(__global __read_only  float* f,
                              __global __write_only float* moments)
{
    const unsigned int gid = get_global_id(1)*${nX} + get_global_id(0);

    __global __read_only float* preshifted_f = f + gid;

% for i in range(0,len(c)):
    const float f_curr_${i} = preshifted_f[${i*nCells}];
% endfor

% for i, expr in enumerate(moments_helper):
    const float ${expr[0]} = ${ccode(expr[1])};
% endfor

% for i, expr in enumerate(moments_assignment):
    moments[${i*nCells} + gid] = ${ccode(expr.rhs)};
% endfor
}"""


class D2Q9_BGK_Lattice:
    def idx(self, x, y):
        return y * self.nX + x;

    def __init__(self, nX, nY):
        self.nX = nX
        self.nY = nY
        self.nCells = nX * nY
        self.tick = True

        self.platform = cl.get_platforms()[0]
        self.context  = cl.Context(properties=[(cl.context_properties.PLATFORM, self.platform)])
        self.queue = cl.CommandQueue(self.context)

        self.np_moments = []
        self.np_material = numpy.ndarray(shape=(self.nCells, 1), dtype=numpy.int32)

        self.setup_geometry()

        self.cl_pop_a = cl.Buffer(self.context, mf.READ_WRITE, size=9*self.nCells*numpy.float32(0).nbytes)
        self.cl_pop_b = cl.Buffer(self.context, mf.READ_WRITE, size=9*self.nCells*numpy.float32(0).nbytes)

        self.cl_moments  = cl.Buffer(self.context, mf.WRITE_ONLY, size=3*self.nCells*numpy.float32(0).nbytes)
        self.cl_material = cl.Buffer(self.context, mf.READ_ONLY  | mf.USE_HOST_PTR, hostbuf=self.np_material)

        self.build_kernel()

        self.program.equilibrilize(self.queue, (self.nX,self.nY), (32,1), self.cl_pop_a, self.cl_pop_b).wait()

    def setup_geometry(self):
        self.np_material[:] = 0
        for x in range(1,self.nX-1):
            for y in range(1,self.nY-1):
                if x == 1 or y == 1 or x == self.nX-2 or y == self.nY-2:
                    self.np_material[self.idx(x,y)] = 2
                else:
                    self.np_material[self.idx(x,y)] = 1

    def build_kernel(self):
        program_src = Template(kernel).render(
            nX     = self.nX,
            nY     = self.nY,
            nCells = self.nCells,
            tau    = '0.8f',
            moments_helper     = D2Q9.moments_opt[0],
            moments_assignment = D2Q9.moments_opt[1],
            collide_helper     = D2Q9.collide_opt[0],
            collide_assignment = D2Q9.collide_opt[1],
            c     = D2Q9.c,
            w     = D2Q9.w,
            ccode = sympy.ccode
        )
        self.program = cl.Program(self.context, program_src).build()

    def collect_moments(self):
        moments = numpy.ndarray(shape=(3, self.nCells), dtype=numpy.float32)

        if self.tick:
            self.program.collect_moments(self.queue, (self.nX,self.nY), (32,1), self.cl_pop_b, self.cl_moments)
        else:
            self.program.collect_moments(self.queue, (self.nX,self.nY), (32,1), self.cl_pop_a, self.cl_moments)

        cl.enqueue_copy(LBM.queue, moments, LBM.cl_moments).wait();
        self.np_moments.append(moments)

    def evolve(self):
        if self.tick:
            self.tick = False
            self.program.collide_and_stream(self.queue, (self.nX,self.nY), (32,1), self.cl_pop_a, self.cl_pop_b, self.cl_material)
        else:
            self.tick = True
            self.program.collide_and_stream(self.queue, (self.nX,self.nY), (32,1), self.cl_pop_b, self.cl_pop_a, self.cl_material)

    def sync(self):
        self.queue.finish()

    def generate_moment_plots(self):
        for i, moments in enumerate(self.np_moments):
            print("Generating plot %d of %d." % (i+1, len(self.np_moments)))

            density = numpy.ndarray(shape=(self.nY-2, self.nX-2))
            for y in range(1,self.nY-1):
                for x in range(1,self.nX-1):
                    density[y-1,x-1] = moments[0,self.idx(x,y)]

            plt.figure(figsize=(10, 10))
            plt.imshow(density, origin='lower', vmin=0.2, vmax=2.0, cmap=plt.get_cmap('seismic'))
            plt.savefig("result/density_" + str(i) + ".png", bbox_inches='tight', pad_inches=0)

        self.np_moments = []


def MLUPS(cells, steps, time):
    return cells * steps / time * 1e-6

nUpdates = 1000
nStat = 100

print("Initializing simulation...\n")

LBM = D2Q9_BGK_Lattice(1024, 1024)

print("Starting simulation using %d cells...\n" % LBM.nCells)

lastStat = time.time()

for i in range(1,nUpdates+1):
    LBM.evolve()

    if i % nStat == 0:
        LBM.sync()
        print("i = %4d; %3.0f MLUPS" % (i, MLUPS(LBM.nCells, nStat, time.time() - lastStat)))
        LBM.collect_moments()
        lastStat = time.time()

print("\nConcluded simulation.\n")

LBM.generate_moment_plots()