[GRASS-dev] G_put_raster_row and OpenMP

[Yann]

Hello,

I am trying to include OpenMP coding into raster processing so that each row 
can be processed by a different process.

The problem faced is that while row number 1 and 2 are still processing, row 
number 3 may already have an ouput for wirting in the output file. Therefore 
we would need to specify the row number to write the ouput row to.

Right now,

int G_put_raster_row (int fd, const void * buf, RASTER_MAP_TYPE data_type)

does not include row number specification. So I tried to find other functions 
in put_row.c:

int G_put_map_row_random (int fd, const CELL * buf, int row, int col, int n)

This function is giving control to the data (row,col) location. However it 
writes only CELL type of data, which is limiting a lot what is possible to do 
with it in remote sensing processing.

Ideally, what we would be looking for is a G_put_raster_random_row() function, 
giving only the row input location would be fine actually, since distributed 
row processing is faster than pixel-wise.

I dont know what are the plans or interests to produce raster code that goes 
this way, but this is something simple I believe would help OpenMP coding.

If people dont want to do it, I could try doing it.

If I missed a major concept, please do not hesitate to correct me :-)

Yann