95 lines
2.6 KiB
C
95 lines
2.6 KiB
C
/*
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* IOchain - Distribute a chain of dependant IO events amoung threads.
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*
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* This file is part of Bitshuffle
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* Author: Kiyoshi Masui <kiyo@physics.ubc.ca>
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* Website: http://www.github.com/kiyo-masui/bitshuffle
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* Created: 2014
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*
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* See LICENSE file for details about copyright and rights to use.
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*
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*
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* Header File
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*
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* Similar in concept to a queue. Each task includes reading an input
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* and writing output, but the location of the input/output (the pointers)
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* depend on the previous item in the chain.
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*
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* This is designed for parallelizing blocked compression/decompression IO,
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* where the destination of a compressed block depends on the compressed size
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* of all previous blocks.
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*
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* Implemented with OpenMP locks.
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*
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*
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* Usage
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* -----
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* - Call `ioc_init` in serial block.
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* - Each thread should create a local variable *size_t this_iter* and
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* pass its address to all function calls. Its value will be set
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* inside the functions and is used to identify the thread.
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* - Each thread must call each of the `ioc_get*` and `ioc_set*` methods
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* exactly once per iteration, starting with `ioc_get_in` and ending
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* with `ioc_set_next_out`.
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* - The order (`ioc_get_in`, `ioc_set_next_in`, *work*, `ioc_get_out`,
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* `ioc_set_next_out`, *work*) is most efficient.
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* - Have each thread call `ioc_end_pop`.
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* - `ioc_get_in` is blocked until the previous entry's
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* `ioc_set_next_in` is called.
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* - `ioc_get_out` is blocked until the previous entry's
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* `ioc_set_next_out` is called.
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* - There are no blocks on the very first iteration.
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* - Call `ioc_destroy` in serial block.
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* - Safe for num_threads >= IOC_SIZE (but less efficient).
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*
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*/
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#ifndef IOCHAIN_H
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#define IOCHAIN_H
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#include <stdlib.h>
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#ifdef _OPENMP
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#include <omp.h>
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#endif
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#define IOC_SIZE 33
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typedef struct ioc_ptr_and_lock {
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#ifdef _OPENMP
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omp_lock_t lock;
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#endif
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void *ptr;
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} ptr_and_lock;
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typedef struct ioc_const_ptr_and_lock {
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#ifdef _OPENMP
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omp_lock_t lock;
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#endif
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const void *ptr;
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} const_ptr_and_lock;
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typedef struct ioc_chain {
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#ifdef _OPENMP
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omp_lock_t next_lock;
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#endif
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size_t next;
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const_ptr_and_lock in_pl[IOC_SIZE];
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ptr_and_lock out_pl[IOC_SIZE];
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} ioc_chain;
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void ioc_init(ioc_chain *C, const void *in_ptr_0, void *out_ptr_0);
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void ioc_destroy(ioc_chain *C);
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const void * ioc_get_in(ioc_chain *C, size_t *this_iter);
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void ioc_set_next_in(ioc_chain *C, size_t* this_iter, void* in_ptr);
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void * ioc_get_out(ioc_chain *C, size_t *this_iter);
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void ioc_set_next_out(ioc_chain *C, size_t *this_iter, void* out_ptr);
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#endif // IOCHAIN_H
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