Hi! Thanks for answering! Figured it out in the end... ------------------------------------------- typedef std::pair< const int, ShmNode> MyPair; typedef boost::shmem::allocator < MyPair, boost::shmem::named_shared_object::segment_manager> MyAlloc; typedef boost::shmem::map< const int, ShmNode, std::less<const int>, MyAlloc> MyMap; (...) ShmNode shmNode1(1, 2); ShmNode shmNode2(3, 4); ShmNode shmNode3(5, 6); MyPair myPair1(1, shmNode1); MyPair myPair2(2, shmNode2); MyPair myPair3(3, shmNode3); table->insert(myPair3); table->insert(myPair1); table->insert(myPair2); ------------------------------------------- Still, can anybody explain what's the purpose of "comparator" and "nodesAlloc" in the following piece of code? I found no documentation whatsoever regarding this, and I managed to compile it by pure accident. Why is there a need for a second comparator when one was already defined for MyMap. Same story with the allocator... ------------------------------------------- MyAlloc nodesAlloc(segment.get_segment_manager()); std::less<const int> comparator; MyMap *table = segment.construct<MyMap>("table")(comparator, nodesAlloc); ------------------------------------------- Regards, Szilard On 8/1/06, Adam Lewis wrote:

The problem is you are storing pointers in the map, which are not in the address space of proc#2. Check http://ice.prohosting.com/newfunk/boost/libs/shmem/doc/html/shmem/limitation...

On 8/1/06, Pataki Szilard wrote:

...

Hello,

I have a problem retrieving objects from a map placed in shared memory. I have two processes:

proc#1: creates the shared memory, puts a map into it and populates it with objects proc#2: connects to the shared memory and tries to read out the objects from the map

Whenever I try to read out the objects from the map, I get zeroes for the internal members (a, b).

The class definition for the objects: -------------------------------------------------- class ShmNode { private: int a; int b; public: ShmNode(); ShmNode(int newa, int newb); ~ShmNode(); void set(int newa, int newb); int getA(); int getB(); }; --------------------------------------------------

I'm posting the source codes for the two programs. I removed the synchronization stuff with semaphores for the sake of clarity:

Proc#1: -------------------------------------------------- #include #include #include #include #include

#include <iostream> #include "../shmem/ShmNode.hpp"

typedef std::pair< const int, ShmNode*> MyPair;

typedef boost::shmem::allocator < MyPair,

boost::shmem::named_shared_object::segment_manager> MyAlloc;

typedef boost::shmem::map< const int, ShmNode*, std::less<const int>, MyAlloc> MyMap;

int main() { boost::shmem::named_shared_object segment;

segment.create("/myshmem", 20000);

MyAlloc nodesAlloc(segment.get_segment_manager ()); std::less<const int> comparator;

MyMap *table = segment.construct<MyMap>("table")(comparator, nodesAlloc);

MyPair myPair1(1, new ShmNode(1,2)); MyPair myPair2(2, new ShmNode(3,4)); MyPair myPair3(3, new ShmNode(5,6));

table->insert(myPair3); table->insert(myPair1); table->insert(myPair2);

return 0; } --------------------------------------------------

Proc#2 -------------------------------------------------- /* same includes */

/* same typedefs */

int main() { boost::shmem::named_shared_object segment; segment.open("/myshmem");

MyMap *table = segment.find<MyMap>("table").first;

std::cout << "table size: " << table->size() << std::endl;

MyMap::iterator iter; for (iter = table->begin(); ; iter++) { if (iter == table->end()) break; std::cout << iter->second->getA() << " " << iter->second->getB() << std::endl; } return 0; } --------------------------------------------------

The problem once again: in proc#2, iter->second->getA() and iter->second->getB() return 0. If I put the same loop into proc#1, the correct values are returned. As a further hint, the size of the map object in proc#2 is returned correctly (=3).

What am I doing wrong?

Regards, Szilard _______________________________________________ Boost-users mailing list Boost-users@lists.boost.org http://lists.boost.org/mailman/listinfo.cgi/boost-users

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