/*
 *   Project: silx: filtered backprojection
 *
 *   Copyright (C) 2016-2017 European Synchrotron Radiation Facility
 *                           Grenoble, France
 *
 *   Principal authors: A. Mirone
 *                      P. Paleo
 *
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
 * conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */


/*******************************************************************************/
/************************ GPU VERSION (with textures) **************************/
/*******************************************************************************/


kernel void backproj_kernel(
    int num_proj,
    int num_bins,
    float axis_position,
    global float *d_SLICE,
    read_only image2d_t d_sino,
    float gpu_offset_x,
    float gpu_offset_y,
    global float * d_cos_s,  // precalculated cos(theta[i])
    global float* d_sin_s,   // precalculated sin(theta[i])
    global float* d_axis_s,  // array of axis positions (n_projs)
    local float* shared2)    // 768B of local mem
{
    const sampler_t sampler = CLK_NORMALIZED_COORDS_FALSE | CLK_ADDRESS_CLAMP_TO_EDGE | CLK_FILTER_LINEAR;
    const int tidx = get_local_id(0); //threadIdx.x;
    const int bidx = get_group_id(0); //blockIdx.x;
    const int tidy = get_local_id(1); //threadIdx.y;
    const int bidy = get_group_id(1); //blockIdx.y;

    //~ local float shared[768];
    //~ float  * sh_sin  = shared;
    //~ float  * sh_cos  = shared+256;
    //~ float  * sh_axis = sh_cos+256;

    local float sh_cos[256];
    local float sh_sin[256];
    local float sh_axis[256];

    float pcos, psin;
    float h0, h1, h2, h3;
    const float apos_off_x= gpu_offset_x - axis_position ;
    const float apos_off_y= gpu_offset_y - axis_position ;
    float acorr05;
    float res0 = 0, res1 = 0, res2 = 0, res3 = 0;

    const float bx00 = (32 * bidx + 2 * tidx + 0 + apos_off_x  ) ;
    const float by00 = (32 * bidy + 2 * tidy + 0 + apos_off_y  ) ;

    int read=0;
    for(int proj=0; proj<num_proj; proj++) {
        if(proj>=read) {
            barrier(CLK_LOCAL_MEM_FENCE);
            int ip = tidy*16+tidx;
            if( read+ip < num_proj) {
                sh_cos [ip] = d_cos_s[read+ip] ;
                sh_sin [ip] = d_sin_s[read+ip] ;
                sh_axis[ip] = d_axis_s[read+ip] ;
            }
            read=read+256; // 256=16*16 block size
            barrier(CLK_LOCAL_MEM_FENCE);
        }
        pcos = sh_cos[256-read + proj] ;
        psin = sh_sin[256-read + proj] ;

        acorr05 = sh_axis[256 - read + proj] ;

        h0 = (acorr05 + bx00*pcos - by00*psin);
        h1 = (acorr05 + (bx00+0)*pcos - (by00+1)*psin);
        h2 = (acorr05 + (bx00+1)*pcos - (by00+0)*psin);
        h3 = (acorr05 + (bx00+1)*pcos - (by00+1)*psin);

        if(h0>=0 && h0<num_bins) res0 += read_imagef(d_sino, sampler, (float2) (h0 +0.5f,proj +0.5f)).x; // tex2D(texprojs,h0 +0.5f,proj +0.5f);
        if(h1>=0 && h1<num_bins) res1 += read_imagef(d_sino, sampler, (float2) (h1 +0.5f,proj +0.5f)).x; // tex2D(texprojs,h1 +0.5f,proj +0.5f);
        if(h2>=0 && h2<num_bins) res2 += read_imagef(d_sino, sampler, (float2) (h2 +0.5f,proj +0.5f)).x; // tex2D(texprojs,h2 +0.5f,proj +0.5f);
        if(h3>=0 && h3<num_bins) res3 += read_imagef(d_sino, sampler, (float2) (h3 +0.5f,proj +0.5f)).x; // tex2D(texprojs,h3 +0.5f,proj +0.5f);
    }
    d_SLICE[ 32*get_num_groups(0)*(bidy*32+tidy*2+0) + bidx*32 + tidx*2 + 0] = res0;
    d_SLICE[ 32*get_num_groups(0)*(bidy*32+tidy*2+1) + bidx*32 + tidx*2 + 0] = res1;
    d_SLICE[ 32*get_num_groups(0)*(bidy*32+tidy*2+0) + bidx*32 + tidx*2 + 1] = res2;
    d_SLICE[ 32*get_num_groups(0)*(bidy*32+tidy*2+1) + bidx*32 + tidx*2 + 1] = res3;
}





/*******************************************************************************/
/********************* CPU VERSION (without textures) **************************/
/*******************************************************************************/


#define CLIP_MAX(x, N) (fmin(fmax(x, 0.0f), (N - 1.0f)))

#define FLOORCEIL_x(x) {\
    xm = (int) floor(x);\
    xp = (int) ceil(x);\
}

#define ADJACENT_PIXELS_VALS(arr, Nx, y, xm, xp) ((float2) (arr[y*Nx+xm], arr[y*Nx+xp]))

//Simple linear interpolator for working on the GPU
static float linear_interpolation(float2 vals,
                                  float x,
                                  int xm,
                                  int xp)
{
    if (xm == xp)
        return vals.s0;
    else 
        return (vals.s0 * (xp - x)) + (vals.s1 * (x - xm));
}

/**
 *
 *  Same kernel as backproj_kernel, but targets the CPU (no texture)
 *
**/
kernel void backproj_cpu_kernel(
    int num_proj,
    int num_bins,
    float axis_position,
    global float *d_SLICE,
    global float* d_sino,
    float gpu_offset_x,
    float gpu_offset_y,
    global float * d_cos_s, // precalculated cos(theta[i])
    global float * d_sin_s, // precalculated sin(theta[i])
    global float * d_axis_s, // array of axis positions (n_projs)
    local float* shared2)     // 768B of local mem
{
    const int tidx = get_local_id(0); //threadIdx.x;
    const int bidx = get_group_id(0); //blockIdx.x;
    const int tidy = get_local_id(1); //threadIdx.y;
    const int bidy = get_group_id(1); //blockIdx.y;

    local float sh_cos[256];
    local float sh_sin[256];
    local float sh_axis[256];

    float pcos, psin;
    float h0, h1, h2, h3;
    const float apos_off_x= gpu_offset_x - axis_position ;
    const float apos_off_y= gpu_offset_y - axis_position ;
    float acorr05;
    float res0 = 0, res1 = 0, res2 = 0, res3 = 0;

    const float bx00 = (32 * bidx + 2 * tidx + 0 + apos_off_x  ) ;
    const float by00 = (32 * bidy + 2 * tidy + 0 + apos_off_y  ) ;

    int read=0;
    for(int proj=0; proj<num_proj; proj++) {
        if(proj>=read) {
            barrier(CLK_LOCAL_MEM_FENCE);
            int ip = tidy*16+tidx;
            if( read+ip < num_proj) {
                sh_cos [ip] = d_cos_s[read+ip] ;
                sh_sin [ip] = d_sin_s[read+ip] ;
                sh_axis[ip] = d_axis_s[read+ip] ;
            }
            read=read+256; // 256=16*16 block size
            barrier(CLK_LOCAL_MEM_FENCE);
        }
        pcos = sh_cos[256-read + proj] ;
        psin = sh_sin[256-read + proj] ;

        acorr05 = sh_axis[256 - read + proj] ;

        h0 = (acorr05 + bx00*pcos - by00*psin);
        h1 = (acorr05 + (bx00+0)*pcos - (by00+1)*psin);
        h2 = (acorr05 + (bx00+1)*pcos - (by00+0)*psin);
        h3 = (acorr05 + (bx00+1)*pcos - (by00+1)*psin);
	
	
	float x;
	int ym, xm, xp;
	ym = proj;
	float2 vals;

	if(h0>=0 && h0<num_bins) { 
	    x = CLIP_MAX(h0, num_bins); 
	    FLOORCEIL_x(x);
	    vals = ADJACENT_PIXELS_VALS(d_sino, num_bins, ym, xm, xp);
	    res0 += linear_interpolation(vals, x, xm, xp);
	}
        if(h1>=0 && h1<num_bins) {
	    x = CLIP_MAX(h1, num_bins); 
	    FLOORCEIL_x(x);
	    vals = ADJACENT_PIXELS_VALS(d_sino, num_bins, ym, xm, xp);
	    res1 += linear_interpolation(vals, x, xm, xp);
        }
        if(h2>=0 && h2<num_bins) {
	    x = CLIP_MAX(h2, num_bins); 
	    FLOORCEIL_x(x);
	    vals = ADJACENT_PIXELS_VALS(d_sino, num_bins, ym, xm, xp);
	    res2 += linear_interpolation(vals, x, xm, xp);
        }
        if(h3>=0 && h3<num_bins) {
	    x = CLIP_MAX(h3, num_bins); 
	    FLOORCEIL_x(x);
	    vals = ADJACENT_PIXELS_VALS(d_sino, num_bins, ym, xm, xp);
	    res3 += linear_interpolation(vals, x, xm, xp);
        }
    }
    d_SLICE[ 32*get_num_groups(0)*(bidy*32+tidy*2+0) + bidx*32 + tidx*2 + 0] = res0;
    d_SLICE[ 32*get_num_groups(0)*(bidy*32+tidy*2+1) + bidx*32 + tidx*2 + 0] = res1;
    d_SLICE[ 32*get_num_groups(0)*(bidy*32+tidy*2+0) + bidx*32 + tidx*2 + 1] = res2;
    d_SLICE[ 32*get_num_groups(0)*(bidy*32+tidy*2+1) + bidx*32 + tidx*2 + 1] = res3;
}







/*******************************************************************************/
/************************** OLD STUFF, for tinkering  **************************/
/*******************************************************************************/




/// arr(xm, ym), arr(xm, yp), arr(xp, yp), arr(xp, ym)
//~ #define ADJACENT_PIXELS_VALS2(arr, Nx, xm, xp, ym, yp) ((float4) (arr[ym*Nx + xm], arr[yp*Nx + xm], arr[yp*Nx + xp], arr[ym*Nx + xp]))


/**  xm, xp, ym, yp  **/
//~ #define ADJACENT_PIXELS_COORDS(x, y) ((int4)((int) floor(x), (int) ceil(x), (int) floor(y), (int) ceil(y)))

/**
        (xm, ym)        (xp, ym)
                 (x, y)
        (xm, yp)        (xp, yp)
**/
/// arr(xm, ym), arr(xm, yp), arr(xp, yp), arr(xp, ym)
//~ #define ADJACENT_PIXELS_VALS(arr, Nx, coords) ((float4) (arr[coords.s2*Nx + coords.s0], arr[coords.s3*Nx + coords.s0], arr[coords.s3*Nx + coords.s1], arr[coords.s2*Nx + coords.s1]))


/**  xm, xp  **/
//~ #define ADJACENT_PIXELS_COORDS2(x) ((int2)((int) floor(x), (int) ceil(x)))



/*
float bilinear_interpolation(
    float x,  // x position in the image
    float y,  // y position in the image
    int Nx,   // image width 
    int Ny,   // image height
    int4 adj_coords, 
    float4 adj_vals
) {
    float val;
    float tol = 0.001f; // CHECKME
    val = y - adj_coords.s2;
    if ((x - adj_coords.s0) < tol && (y - adj_coords.s2) < tol) val = adj_vals.s0; 
    else if ((adj_coords.s1 - x) < tol && (adj_coords.s3 - y) < tol) val = adj_vals.s2; 
    else {
        // Mirror - TODO: clamp ?
        if (adj_coords.s0 < 0) adj_coords.s0 = 0;
        if (adj_coords.s1 >= Nx) adj_coords.s1 = Nx - 1;
        if (adj_coords.s2 < 0) adj_coords.s2 = 0;
        if (adj_coords.s3 >= Ny) adj_coords.s3 = Ny -1;
	if (adj_coords.s0 >= Nx) adj_coords.s0 = Nx - 1;
	if (adj_coords.s2 >= Ny) adj_coords.s2 = Ny -1;
        // Interp
        val = adj_vals.s1*(adj_coords.s1-x)*(y-adj_coords.s2)
                    + adj_vals.s2 *(x-adj_coords.s0)*(y-adj_coords.s2)
                    + adj_vals.s0 *(adj_coords.s1-x)*(adj_coords.s3-y) 
                    + adj_vals.s3 *(x-adj_coords.s0)*(adj_coords.s3-y); 

    }
    return val;
}
*/


/*
__kernel void backproj_cpu_kernel_good(
    int num_proj,
    int num_bins,
    float axis_position,
    __global float *d_SLICE,
    __global float* d_sino,
    float gpu_offset_x,
    float gpu_offset_y,
    __global float * d_cos_s, // precalculated cos(theta[i])
    __global float * d_sin_s, // precalculated sin(theta[i])
    __global float * d_axis_s, // array of axis positions (n_projs)
    __local float* shared2)     // 768B of local mem
{
    const int tidx = get_local_id(0); //threadIdx.x;
    const int bidx = get_group_id(0); //blockIdx.x;
    const int tidy = get_local_id(1); //threadIdx.y;
    const int bidy = get_group_id(1); //blockIdx.y;

    //~ __local float shared[768];
    //~ float  * sh_sin  = shared;
    //~ float  * sh_cos  = shared+256;
    //~ float  * sh_axis = sh_cos+256;

    __local float sh_cos[256];
    __local float sh_sin[256];
    __local float sh_axis[256];

    float pcos, psin;
    float h0, h1, h2, h3;
    const float apos_off_x= gpu_offset_x - axis_position ;
    const float apos_off_y= gpu_offset_y - axis_position ;
    float acorr05;
    float res0 = 0, res1 = 0, res2 = 0, res3 = 0;

    const float bx00 = (32 * bidx + 2 * tidx + 0 + apos_off_x  ) ;
    const float by00 = (32 * bidy + 2 * tidy + 0 + apos_off_y  ) ;

    int read=0;
    for(int proj=0; proj<num_proj; proj++) {
        if(proj>=read) {
            barrier(CLK_LOCAL_MEM_FENCE);
            int ip = tidy*16+tidx;
            if( read+ip < num_proj) {
                sh_cos [ip] = d_cos_s[read+ip] ;
                sh_sin [ip] = d_sin_s[read+ip] ;
                sh_axis[ip] = d_axis_s[read+ip] ;
            }
            read=read+256; // 256=16*16 block size
            barrier(CLK_LOCAL_MEM_FENCE);
        }
        pcos = sh_cos[256-read + proj] ;
        psin = sh_sin[256-read + proj] ;

        acorr05 = sh_axis[256 - read + proj] ;

        h0 = (acorr05 + bx00*pcos - by00*psin);
        h1 = (acorr05 + (bx00+0)*pcos - (by00+1)*psin);
        h2 = (acorr05 + (bx00+1)*pcos - (by00+0)*psin);
        h3 = (acorr05 + (bx00+1)*pcos - (by00+1)*psin);
	
	
	float x, val;
	float tol = 0.001f; // CHECKME
	float y = proj + 0.5f;
	int ym = (int) floor(y);
	int yp = (int) ceil(y);
	int xm, xp;
	
	//
	int i0, i1, j0, j1;
	float d0, d1, x0, x1, y0, y1;
	d0 = fmin(fmax(proj+0*0.5f, 0.0f), (num_proj - 1.0f));
	x0 = floor(d0);
	x1 = ceil(d0);
	i0 = (int) x0;
	i1 = (int) x1;

	if(h0>=0 && h0<num_bins) { 
            d1 = fmin(fmax(h0+0*0.5f, 0.0f), (num_bins - 1.0f));
	    y0 = floor(d1);
	    y1 = ceil(d1);
	    j0 = (int) y0;
	    j1 = (int) y1;
	    
	    if ((i0 == i1) && (j0 == j1))
		val = d_sino[i0*num_bins + j0]; //self.data[i0, j0]
	    else if (i0 == i1)
		val = (d_sino[i0*num_bins + j0] * (y1 - d1)) + (d_sino[i0*num_bins + j1] * (d1 - y0)); // self.data[i0, j0], self.data[i0, j1]
	    else if (j0 == j1)
		val = (d_sino[i0*num_bins + j0] * (x1 - d0)) + (d_sino[i1*num_bins + j0] * (d0 - x0)); // i0, j0  ;  i1, j0
	    else
		val = (d_sino[i0*num_bins + j0] * (x1 - d0) * (y1 - d1))  // i0, j0
		    + (d_sino[i1*num_bins + j0] * (d0 - x0) * (y1 - d1))  // i1, j0
		    + (d_sino[i0*num_bins + j1] * (x1 - d0) * (d1 - y0))  // i0, j1
		    + (d_sino[i1*num_bins + j1] * (d0 - x0) * (d1 - y0));  // i1, j1

	    res0 += val;
	}
        if(h1>=0 && h1<num_bins) {
	    //~ int4 coords = ADJACENT_PIXELS_COORDS(h1 +0.5f, proj +0.5f);
	    //~ res1 += bilinear_interpolation(h1 +0.5f, proj +0.5f, num_bins, num_proj, coords, ADJACENT_PIXELS_VALS(d_sino, num_bins, coords)); //tex2D(texProjes,h1 +0.5f,proj +0.5f);
            d1 = fmin(fmax(h1+0*0.5f, 0.0f), (num_bins - 1.0f));
	    y0 = floor(d1);
	    y1 = ceil(d1);
	    j0 = (int) y0;
	    j1 = (int) y1;
	    
	    if ((i0 == i1) && (j0 == j1))
		val = d_sino[i0*num_bins + j0]; //self.data[i0, j0]
	    else if (i0 == i1)
		val = (d_sino[i0*num_bins + j0] * (y1 - d1)) + (d_sino[i0*num_bins + j1] * (d1 - y0)); // self.data[i0, j0], self.data[i0, j1]
	    else if (j0 == j1)
		val = (d_sino[i0*num_bins + j0] * (x1 - d0)) + (d_sino[i1*num_bins + j0] * (d0 - x0)); // i0, j0  ;  i1, j0
	    else
		val = (d_sino[i0*num_bins + j0] * (x1 - d0) * (y1 - d1))  // i0, j0
		    + (d_sino[i1*num_bins + j0] * (d0 - x0) * (y1 - d1))  // i1, j0
		    + (d_sino[i0*num_bins + j1] * (x1 - d0) * (d1 - y0))  // i0, j1
		    + (d_sino[i1*num_bins + j1] * (d0 - x0) * (d1 - y0));  // i1, j1


	    res1 += val;
        }
        if(h2>=0 && h2<num_bins) {
	    //~ int4 coords = ADJACENT_PIXELS_COORDS(h2 +0.5f, proj +0.5f);
	    //~ res2 += 0; //bilinear_interpolation(h2 +0.5f, proj +0.5f, num_bins, num_proj, coords, ADJACENT_PIXELS_VALS(d_sino, num_bins, coords)); //tex2D(texProjes,h2 +0.5f,proj +0.5f);
            d1 = fmin(fmax(h2+0*0.5f, 0.0f), (num_bins - 1.0f));
	    y0 = floor(d1);
	    y1 = ceil(d1);
	    j0 = (int) y0;
	    j1 = (int) y1;
	    
	    if ((i0 == i1) && (j0 == j1))
		val = d_sino[i0*num_bins + j0]; //self.data[i0, j0]
	    else if (i0 == i1)
		val = (d_sino[i0*num_bins + j0] * (y1 - d1)) + (d_sino[i0*num_bins + j1] * (d1 - y0)); // self.data[i0, j0], self.data[i0, j1]
	    else if (j0 == j1)
		val = (d_sino[i0*num_bins + j0] * (x1 - d0)) + (d_sino[i1*num_bins + j0] * (d0 - x0)); // i0, j0  ;  i1, j0
	    else
		val = (d_sino[i0*num_bins + j0] * (x1 - d0) * (y1 - d1))  // i0, j0
		    + (d_sino[i1*num_bins + j0] * (d0 - x0) * (y1 - d1))  // i1, j0
		    + (d_sino[i0*num_bins + j1] * (x1 - d0) * (d1 - y0))  // i0, j1
		    + (d_sino[i1*num_bins + j1] * (d0 - x0) * (d1 - y0));  // i1, j1

	    res2+= val;
        }
        if(h3>=0 && h3<num_bins) {
	    //~ int4 coords = ADJACENT_PIXELS_COORDS(h3 +0.5f, proj +0.5f);
	    //~ res3 += 0; //bilinear_interpolation(h3 +0.5f, proj +0.5f, num_bins, num_proj, coords, ADJACENT_PIXELS_VALS(d_sino, num_bins, coords)); //tex2D(texProjes,h3 +0.5f,proj +0.5f);
            d1 = fmin(fmax(h3+0*0.5f, 0.0f), (num_bins - 1.0f));
	    y0 = floor(d1);
	    y1 = ceil(d1);
	    j0 = (int) y0;
	    j1 = (int) y1;
	    
	    if ((i0 == i1) && (j0 == j1))
		val = d_sino[i0*num_bins + j0]; //self.data[i0, j0]
	    else if (i0 == i1)
		val = (d_sino[i0*num_bins + j0] * (y1 - d1)) + (d_sino[i0*num_bins + j1] * (d1 - y0)); // self.data[i0, j0], self.data[i0, j1]
	    else if (j0 == j1)
		val = (d_sino[i0*num_bins + j0] * (x1 - d0)) + (d_sino[i1*num_bins + j0] * (d0 - x0)); // i0, j0  ;  i1, j0
	    else
		val = (d_sino[i0*num_bins + j0] * (x1 - d0) * (y1 - d1))  // i0, j0
		    + (d_sino[i1*num_bins + j0] * (d0 - x0) * (y1 - d1))  // i1, j0
		    + (d_sino[i0*num_bins + j1] * (x1 - d0) * (d1 - y0))  // i0, j1
		    + (d_sino[i1*num_bins + j1] * (d0 - x0) * (d1 - y0));  // i1, j1

	    res3 += val;
        }
    }
    d_SLICE[ 32*get_num_groups(0)*(bidy*32+tidy*2+0) + bidx*32 + tidx*2 + 0] = res0;
    d_SLICE[ 32*get_num_groups(0)*(bidy*32+tidy*2+1) + bidx*32 + tidx*2 + 0] = res1;
    d_SLICE[ 32*get_num_groups(0)*(bidy*32+tidy*2+0) + bidx*32 + tidx*2 + 1] = res2;
    d_SLICE[ 32*get_num_groups(0)*(bidy*32+tidy*2+1) + bidx*32 + tidx*2 + 1] = res3;
}
*/