| Top |  |
 |
 |
 |
Functions
| void * | vips_thread_state_set () |
| VipsThreadState * | vips_thread_state_new () |
| VipsThreadState * | (*VipsThreadStartFn) () |
| int | (*VipsThreadpoolAllocateFn) () |
| int | (*VipsThreadpoolWorkFn) () |
| int | (*VipsThreadpoolProgressFn) () |
| int | vips_threadpool_run () |
| void | vips_get_tile_size () |
Description
A threadpool which allows reusing already started threads. Implementing this can be tedious and error-prone. Therefore we use the GLib provided threadpool for our convenience. An added advantage is, that the threads can be shared between the different subsystems, when they are using GLib.
The threadpool is created during vips_init() and is destroyed by
vips_shutdown().
vips_threadpool_run() loops a set of threads over an image. Threads take it in turns to allocate units of work (a unit might be a tile in an image), then run in parallel to process those units. An optional progress function can be used to give feedback.
Functions
VipsThreadpoolAllocateFn ()
int (*VipsThreadpoolAllocateFn) (VipsThreadState *state,void *a,gboolean *stop);
This function is called to allocate a new work unit for the thread. It is always single-threaded, so it can modify per-pool state (such as a counter).
a
, b
, c
are the values supplied to the call to
vips_threadpool_run().
It should set stop
to TRUE to indicate that no work could be allocated
because the job is done.
See also: vips_threadpool_run().
VipsThreadpoolWorkFn ()
int (*VipsThreadpoolWorkFn) (VipsThreadState *state,void *a);
This function is called to process a work unit. Many copies of this can run at once, so it should not write to the per-pool state. It can write to per-thread state.
a
, b
, c
are the values supplied to the call to
vips_threadpool_run().
See also: vips_threadpool_run().
VipsThreadpoolProgressFn ()
int
(*VipsThreadpoolProgressFn) (void *a);
This function is called by the main thread once for every work unit processed. It can be used to give the user progress feedback.
See also: vips_threadpool_run().
vips_threadpool_run ()
int vips_threadpool_run (VipsImage *im,VipsThreadStartFn start,VipsThreadpoolAllocateFn allocate,VipsThreadpoolWorkFn work,VipsThreadpoolProgressFn progress,void *a);
This function runs a set of threads over an image. It will use a newly
created or reused thread within the VipsThreadPool. Each thread first calls
start
to create new per-thread state, then runs
allocate
to set up a new work unit (perhaps the next tile in an image, for
example), then work
to process that work unit. After each unit is
processed, progress
is called, so that the operation can give
progress feedback. progress
may be NULL.
The object returned by start
must be an instance of a subclass of
VipsThreadState. Use this to communicate between allocate
and work
.
allocate
is always single-threaded (so it can write to the
per-pool state), whereas start
and work
can be executed concurrently.
progress
is always called by
the main thread (ie. the thread which called vips_threadpool_run()).
See also: vips_concurrency_set().
vips_get_tile_size ()
void vips_get_tile_size (VipsImage *im,int *tile_width,int *tile_height,int *n_lines);
Pick a tile size and a buffer height for this image and the current
value of vips_concurrency_get(). The buffer height
will always be a multiple of tile_height.
The buffer height is the height of each buffer we fill in sink disc. Since we have two buffers, the largest range of input locality is twice the output buffer size, plus whatever margin we add for things like convolution.
[method]