FREEZEGROUP(3PVM)

💖 FREEZEGROUP — pvm_freezegroup 💖

okay bestie, we're diving into PVM Version 3.4's group-freezing manual page, aka pvm_freezegroup — the routine that freezes dynamic group membership and caches all that info locally. it's giving "we're locking the group in place, no new members, no cap." 🧊✨

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✨ NAME ✨

pvm_freezegroup — freezes dynamic group membership and caches the info locally. it's literally the "okay everybody freeze 🥶" button for your group.

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🌸 SYNOPSIS 🌸

C version, look at her:

int info = pvm_freezegroup( char *group , int size)

Fortran version, same energy different font:

call pvmffreezegroup( group, size, info )

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🎀 PARAMETERS 🎀

• group — a character string, the group name of an existing group. you gotta actually have a group first bestie, can't freeze what doesn't exist 💅
• size — the size of the group when it gets frozen. this is the headcount you're locking in.
• info — the size of the group on success. values less than 0 mean there was an error. so if it's negative, something went wrong, and we're sad 😭

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🦋 DESCRIPTION 🦋

so what does pvm_freezegroup actually do? it takes a dynamic group named group and makes it static. periodt. once that happens, the group information gets "cached" by all the group members. it's a whole glow-up from dynamic to static.

⚠️ heads up: pvm_freezegroup is a synchronizing routine, which means it must be called by all group members to actually complete. no skipping, no lurking, everybody participates. it's a group project and everyone's getting a grade.

size tells it how big the dynamic group should be when it gets made static. and here's a cute little shortcut: a value of -1 means "just use the current size of the group, bestie, don't make me count." info returns the error information back to you.

once a dynamic group has been frozen with pvm_freezegroup, all subsequent operations that can be satisfied with local data just use the locally held information. no more asking the server, it's all in your head now 🧠✨

for processes that are outside of the group, the first group call — like, say, pvm_bcast() — will cause the static group information to be copied to the calling process. after that first one, subsequent operations use the local information. so it's a one-time download, then it's offline mode. 📥

but wait — barriers are still arbitrated by the group server. so it's not fully offline, iykyk.

group members should call pvm_lvgroup to leave the group and free any allocated structures that hold the group information. and processes that are not in the group may also call pvm_lvgroup to free any locally allocated structures. in that case, an error code of PvmNotInGroup or PvmNoGroup gets returned to the caller. so like, thanks for the cleanup but also who are you 💀

barriers are always arbitrated by the group server, even if the group has been made static with pvm_freezegroup. and here's the dramatic part: if a process leaves a static group while other processes are waiting at a barrier, then PvmNoGroup is returned to all processes waiting at the barrier. future barrier calls with that defunct static group return the same error. it's over, she's gone, the group is no more 🪦

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🌈 EXAMPLES 🌈

C, serving looks:

inum = pvm_joingroup("worker");
info = pvm_freezegroup( "worker", size );

Fortran, serving the same looks in uppercase:

CALL PVMFJOINGROUP('group2', inum)
CALL PVMFFREEZEGROUP( 'group2', size, info )

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💀 ERRORS 💀

these error conditions can be returned by pvm_freezegroup, and yes we're listing every single one because nobody gets left out:

• PvmSysErr — pvmd was not started or has crashed. the daemon ghosted us 😭
• PvmBadParam — you gave a NULL group name. bestie. you have to name the group.
• PvmDupGroup — trying to freeze a group that is already frozen. she's already frozen!! let her be!! 🧊
• PvmNotInGroup — trying to freeze a group that you are not in. respectfully, this is not your group 💅

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🙈 BUGS 🙈

the drama, the mess, the tea:

• There is no way to unfreeze a group. once frozen, always frozen. no take-backs, no ctrl+z, no nothing. 🥶
• Processes are not notified if a frozen group becomes invalid. so like, they just won't know. ghosted fr fr 👻
• Having a non-member process call pvm_lvgroup to free structures is a bit strange. yeah. we know. the manual knows. it's a little weird, we said what we said.

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👑 SEE ALSO 👑

go read these next bestie, they're part of the lore:

• pvm_barrier(3PVM)
• pvm_lvgroup(3PVM)

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that's the whole page, babe — PVM Version 3.4, dated 16 March 1995, brought to you with love, sass, and full documentation fidelity. mwah 💋🫶