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VipsThreadState

VipsThreadState — pools of worker threads

Stability Level

Stable, unless otherwise indicated

Object Hierarchy

    GObject
    ╰── VipsObject
        ╰── VipsThreadState

Includes

#include <vips/vips.h>

Description

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

vips_thread_state_set ()

void *
vips_thread_state_set (VipsObject *object,
                       void *a,
                       void *b);

vips_thread_state_new ()

VipsThreadState *
vips_thread_state_new (VipsImage *im,
                       void *a);

VipsThreadStartFn ()

VipsThreadState *
(*VipsThreadStartFn) (VipsImage *im,
                      void *a);

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().

Parameters

state

per-thread state

 

a

client data

 

b

client data

 

c

client data

 

stop

set this to signal end of computation

 

Returns

0 on success, or -1 on error

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().

Parameters

state

per-thread state

 

a

client data

 

b

client data

 

c

client data

 

Returns

0 on success, or -1 on error

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().

Parameters

a

client data

 

b

client data

 

c

client data

 

Returns

0 on success, or -1 on error

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. 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 and start are always single-threaded (so they can write to the per-pool state), whereas 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().

Parameters

im

image to loop over

 

start

allocate per-thread state

 

allocate

allocate a work unit

 

work

process a work unit

 

progress

give progress feedback about a work unit, or NULL

 

a

client data

 

Returns

0 on success, or -1 on error.

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.

Parameters

im

image to guess for

 

tile_width

return selected tile width

 

tile_height

return selected tile height

 

n_lines

return buffer height in scanlines

 

Types and Values

See Also

generate
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