make wt_int and wm_int thread safe by ekg · Pull Request #264 · simongog/sdsl-lite

ekg · 2015-08-31T10:24:48Z

This is accomplished by moving m_path_off and m_path_rank_off to the local
context of select (see #263).

Now, grep mutable include/sdsl/*hpp yields only wt_pc.hpp, bp_support_sada, and
csa_sada, all of which have shared caches that will not be thread safe without
changes to the API.

This is accomplished by moving m_path_off and m_path_rank_off to the local context of select (see #263). Now, grep mutable include/sdsl/*hpp yields only wt_pc.hpp, bp_support_sada, and csa_sada, all of which have shared caches that will not be thread safe without changes to the API.

tb-robot · 2015-08-31T10:26:01Z

Can one of the admins verify this patch?

ekg · 2015-08-31T14:22:04Z

I think it might make sense to revert my last push. Trying to understand what I'm seeing here once I try to integrate the changes into another application: https://travis-ci.org/ekg/xg/builds/78046876#L5603-L5645. This wasn't an issue with int_vector<64>.

Here's the text of the error in case it vanishes into travis history:

In file included from sdsl-lite/build/include/sdsl/wavelet_trees.hpp:37:0,
                 from xg.hpp:12,
                 from xg.cpp:1:
sdsl-lite/build/include/sdsl/wt_int.hpp: In instantiation of ‘sdsl::wt_int<t_bitvector, t_rank, t_select, t_select_zero>::size_type sdsl::wt_int<t_bitvector, t_rank, t_select, t_select_zero>::select(sdsl::wt_int<t_bitvector, t_rank, t_select, t_select_zero>::size_type, sdsl::wt_int<t_bitvector, t_rank, t_select, t_select_zero>::value_type) const [with t_bitvector = sdsl::int_vector<1u>; t_rank = sdsl::rank_support_v<1u, 1u>; t_select = sdsl::select_support_mcl<1u, 1u>; t_select_zero = sdsl::select_support_mcl<0u, 1u>; sdsl::wt_int<t_bitvector, t_rank, t_select, t_select_zero>::size_type = long unsigned int; sdsl::wt_int<t_bitvector, t_rank, t_select, t_select_zero>::value_type = long unsigned int]’:
xg.cpp:355:64:   required from here
sdsl-lite/build/include/sdsl/wt_int.hpp:431:60: error: no matching function for call to ‘std::array<long unsigned int, 65ul>::array(unsigned int)’
             std::array<uint64_t, 65> m_path_off(max_level+1);
                                                            ^
sdsl-lite/build/include/sdsl/wt_int.hpp:431:60: note: candidates are:
In file included from /usr/include/c++/4.9/tuple:39:0,
                 from /usr/include/c++/4.9/bits/stl_map.h:63,
                 from /usr/include/c++/4.9/map:61,
                 from xg.hpp:6,
                 from xg.cpp:1:
/usr/include/c++/4.9/array:81:12: note: std::array<long unsigned int, 65ul>::array()
     struct array
            ^
/usr/include/c++/4.9/array:81:12: note:   candidate expects 0 arguments, 1 provided
/usr/include/c++/4.9/array:81:12: note: constexpr std::array<long unsigned int, 65ul>::array(const std::array<long unsigned int, 65ul>&)
/usr/include/c++/4.9/array:81:12: note:   no known conversion for argument 1 from ‘unsigned int’ to ‘const std::array<long unsigned int, 65ul>&’
/usr/include/c++/4.9/array:81:12: note: constexpr std::array<long unsigned int, 65ul>::array(std::array<long unsigned int, 65ul>&&)
/usr/include/c++/4.9/array:81:12: note:   no known conversion for argument 1 from ‘unsigned int’ to ‘std::array<long unsigned int, 65ul>&&’
In file included from sdsl-lite/build/include/sdsl/wavelet_trees.hpp:37:0,
                 from xg.hpp:12,
                 from xg.cpp:1:
sdsl-lite/build/include/sdsl/wt_int.hpp:432:65: error: no matching function for call to ‘std::array<long unsigned int, 65ul>::array(unsigned int)’
             std::array<uint64_t, 65> m_path_rank_off(max_level+1);
                                                                 ^
sdsl-lite/build/include/sdsl/wt_int.hpp:432:65: note: candidates are:
In file included from /usr/include/c++/4.9/tuple:39:0,
                 from /usr/include/c++/4.9/bits/stl_map.h:63,
                 from /usr/include/c++/4.9/map:61,
                 from xg.hpp:6,
                 from xg.cpp:1:
/usr/include/c++/4.9/array:81:12: note: std::array<long unsigned int, 65ul>::array()
     struct array
            ^
/usr/include/c++/4.9/array:81:12: note:   candidate expects 0 arguments, 1 provided
/usr/include/c++/4.9/array:81:12: note: constexpr std::array<long unsigned int, 65ul>::array(const std::array<long unsigned int, 65ul>&)
/usr/include/c++/4.9/array:81:12: note:   no known conversion for argument 1 from ‘unsigned int’ to ‘const std::array<long unsigned int, 65ul>&’
/usr/include/c++/4.9/array:81:12: note: constexpr std::array<long unsigned int, 65ul>::array(std::array<long unsigned int, 65ul>&&)
/usr/include/c++/4.9/array:81:12: note:   no known conversion for argument 1 from ‘unsigned int’ to ‘std::array<long unsigned int, 65ul>&&’

simongog · 2015-08-31T14:30:22Z

why are you passing an argument to the constructor of std::array? The 65 as
second template argument is enough I guess ;)

2015-08-31 16:22 GMT+02:00 Erik Garrison notifications@github.com:

I think it might make sense to revert my last push. Trying to understand
what I'm seeing here once I try to integrate the changes into another
application: https://travis-ci.org/ekg/xg/builds/78046876#L5603-L5645.
This wasn't an issue with int_vector<64>.

Here's the text of the error in case it vanishes into travis history:

In file included from sdsl-lite/build/include/sdsl/wavelet_trees.hpp:37:0,
from xg.hpp:12,
from xg.cpp:1:
sdsl-lite/build/include/sdsl/wt_int.hpp: In instantiation of ‘sdsl::wt_int<t_bitvector, t_rank, t_select, t_select_zero>::size_type sdsl::wt_int<t_bitvector, t_rank, t_select, t_select_zero>::select(sdsl::wt_int<t_bitvector, t_rank, t_select, t_select_zero>::size_type, sdsl::wt_int<t_bitvector, t_rank, t_select, t_select_zero>::value_type) const [with t_bitvector = sdsl::int_vector<1u>; t_rank = sdsl::rank_support_v<1u, 1u>; t_select = sdsl::select_support_mcl<1u, 1u>; t_select_zero = sdsl::select_support_mcl<0u, 1u>; sdsl::wt_int<t_bitvector, t_rank, t_select, t_select_zero>::size_type = long unsigned int; sdsl::wt_int<t_bitvector, t_rank, t_select, t_select_zero>::value_type = long unsigned int]’:
xg.cpp:355:64: required from here
sdsl-lite/build/include/sdsl/wt_int.hpp:431:60: error: no matching function for call to ‘std::array<long unsigned int, 65ul>::array(unsigned int)’
std::array<uint64_t, 65> m_path_off(max_level+1);
^
sdsl-lite/build/include/sdsl/wt_int.hpp:431:60: note: candidates are:
In file included from /usr/include/c++/4.9/tuple:39:0,
from /usr/include/c++/4.9/bits/stl_map.h:63,
from /usr/include/c++/4.9/map:61,
from xg.hpp:6,
from xg.cpp:1:
/usr/include/c++/4.9/array:81:12: note: std::array<long unsigned int, 65ul>::array()
struct array
^
/usr/include/c++/4.9/array:81:12: note: candidate expects 0 arguments, 1 provided
/usr/include/c++/4.9/array:81:12: note: constexpr std::array<long unsigned int, 65ul>::array(const std::array<long unsigned int, 65ul>&)
/usr/include/c++/4.9/array:81:12: note: no known conversion for argument 1 from ‘unsigned int’ to ‘const std::array<long unsigned int, 65ul>&’
/usr/include/c++/4.9/array:81:12: note: constexpr std::array<long unsigned int, 65ul>::array(std::array<long unsigned int, 65ul>&&)
/usr/include/c++/4.9/array:81:12: note: no known conversion for argument 1 from ‘unsigned int’ to ‘std::array<long unsigned int, 65ul>&&’
In file included from sdsl-lite/build/include/sdsl/wavelet_trees.hpp:37:0,
from xg.hpp:12,
from xg.cpp:1:
sdsl-lite/build/include/sdsl/wt_int.hpp:432:65: error: no matching function for call to ‘std::array<long unsigned int, 65ul>::array(unsigned int)’
std::array<uint64_t, 65> m_path_rank_off(max_level+1);
^
sdsl-lite/build/include/sdsl/wt_int.hpp:432:65: note: candidates are:
In file included from /usr/include/c++/4.9/tuple:39:0,
from /usr/include/c++/4.9/bits/stl_map.h:63,
from /usr/include/c++/4.9/map:61,
from xg.hpp:6,
from xg.cpp:1:
/usr/include/c++/4.9/array:81:12: note: std::array<long unsigned int, 65ul>::array()
struct array
^
/usr/include/c++/4.9/array:81:12: note: candidate expects 0 arguments, 1 provided
/usr/include/c++/4.9/array:81:12: note: constexpr std::array<long unsigned int, 65ul>::array(const std::array<long unsigned int, 65ul>&)
/usr/include/c++/4.9/array:81:12: note: no known conversion for argument 1 from ‘unsigned int’ to ‘const std::array<long unsigned int, 65ul>&’
/usr/include/c++/4.9/array:81:12: note: constexpr std::array<long unsigned int, 65ul>::array(std::array<long unsigned int, 65ul>&&)
/usr/include/c++/4.9/array:81:12: note: no known conversion for argument 1 from ‘unsigned int’ to ‘std::array<long unsigned int, 65ul>&&’

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#264 (comment).

ekg · 2015-10-06T12:26:45Z

I'd like to pick this back up as it's continuing to cause issues for me.

Relative to the patch that I proposed, what changes would you require to make this acceptable?

I'm also interested in doing something similar for csa_sada.

mpetri · 2015-10-06T12:36:48Z

just making the buffer in csa_sada local would probably cause lots of allocations which will degrade performance? Have not benchmarked this though.

ekg · 2015-10-06T12:39:11Z

It seems it might hurt performance. That said, mutex locking isn't a great solution.

What might be sensible is to pass a thread-local buffer into the select.

simongog · 2015-10-06T13:51:09Z

Yes, a third argument which is a pointer to a thread-local buffer seems to be the good solution, since it is backward-compatible. If a nullptr is passed we could then just use the old mutable array to still get the same performance for single-threaded program ;)

mpetri · 2015-10-06T23:55:13Z

the buffer is also used in rank_bwt which is called from the suffix_array_helper classes which are called from count() and extract() etc. so it will be quite difficult to adjust all of these and remain backward-compatible.

simongog · 2015-10-07T00:05:38Z

Yes, it is used in those places, but since it is only called with the two arguments it will still work as expected in the single-threaded case. You are certainly right that more adjustments have to be made to make some methods of the CSA (like rank_bwt,count, and extract) work in a multithreaded environment, but I think this is not the point of Erik's request.

mpetri · 2015-10-07T00:14:42Z

well csa_sada::select_bwt() doesn't use the buffer at all so not sure what the problem is here?

mpetri · 2015-10-07T00:15:29Z

also, there is a assert(cc != 255); in there which probably has to removed as we now deal with integer alphabets.

ekg · 2016-03-14T14:31:27Z

How much does the caching help? Could I simply add an option to turn it off to all of the classes that use this kind of non-threadsafe feature?

use stack-allocated memory

87b9334

ekg mentioned this pull request Aug 31, 2015

thread safety jltsiren/gcsa2#9

Closed

revert to int_vector<64>

1d1c988

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make wt_int and wm_int thread safe#264

make wt_int and wm_int thread safe#264
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