c++ - how to use user defined structure in opencl -

i trying explore way use structure in opencl

i first try struct (defined on host)

typedef struct userstruct {      cl_int x;     cl_int y;     cl_int z;     cl_int w; } userstruct; 

and structure (defined on device)

typedef struct userstruct {     int x;     int y;     int z;     int w; } userstruct; 

using defined structure, create 2 buffers (para_input , para_output) , init them different values. kernel function copies value para_input para_output.

the example works fine.

but, when add cl_int16 in struct, copying kernel not work. here modified structure:

typedef struct userstruct {      cl_int x;     cl_int y;     cl_int z;     cl_int w;       cl_int16 vn16; } userstruct; 

and structure (defined on device)

typedef struct userstruct {     int x;     int y;     int z;     int w;      int16 vn16; } userstruct; 

is there requirement align structure on both host , device? or popular way use structure in opencl? thanks.

expanding on comment:

it seems problem caused difference in default structure alignment in c compiler , opencl compiler. namely, c compiler packs structure minimum of 80 bytes, while opencl compiler aligns 128 bytes (which thing performance-wise). can match alignment specifying explicitly: either pack both structures, or align both 128 bytes. see opencl docs , compiler's docs (which, probably, uses same notation) details.

in case, recommend going 128 bytes alignment, unless pressured space. declare structures as:

typedef struct userstruct {      cl_int x;     cl_int y;     cl_int z;     cl_int w;      cl_int16 vn16; } __attribute__ ((aligned (128))) userstruct; 

and analogously host one.

as side note, nothing prevents using same structure both host , device code. cl_ints aliases native types anyway (although explicit alignment specifier still necessary, because structure potentially processed different compilers).