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Fix weighted list RNG on platforms with a different RAND_MAX value #14413

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merged 2 commits into from Dec 15, 2015

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@remyroy @sparr @Malkeus @kevingranade
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commented Dec 13, 2015

Fixes #14410.

@remyroy remyroy changed the title [WIP] Fix weighted list RNG on platforms with different a RAND_MAX value Fix weighted list RNG on platforms with a different RAND_MAX value Dec 13, 2015

src/weighted_list.h Outdated
picked = ( double )rand_ll / ( double )INT_MAX * ( this->total_weight );
}
size_t pick_ent( unsigned int randi ) const override {
double picked = ( double )randi / ( double )RAND_MAX * ( this->total_weight );

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double picked = ( double )(randi%RAND_MAX) / ( double )RAND_MAX * ( this->total_weight );

the modulo operation will make sure the picked number is <total_weight, in cases where randi>RAND_MAX because INT_MAX>RAND_MAX (such as on the windows platform where this bug was identified)
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commented Dec 13, 2015

randi should never be greater than RAND_MAX with our current code using weighted_float_list but for completion, I'll make the modification.
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commented Dec 13, 2015

I would merge this if I could test it on Windows.
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commented Dec 14, 2015

I now have a headache and a copy of CleverRaven:master with your changes compiling on my Windows 7 64bit system. I'll get back to you with the results soon.
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commented Dec 14, 2015

Random vehicles appear to only be spawning in cities. I traveled for several dozen map tiles of non-city roads and didn't see a single vehicle. City car levels seem to be at or slightly above the normal levels. I may have had an unlucky run, I will create a new world and try again.

Edit: I think I was just unlucky the first time around. Second world had a long stretch of road surrounded by forest, I encountered 2 sports cars along the way, seems good to me.

@Malkeus Malkeus referenced this pull request Dec 14, 2015

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Random vehicles not spawning #14410

@kevingranade kevingranade merged commit 6c1a861 into CleverRaven:master Dec 15, 2015
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default This has been rescheduled for testing as the 'master' branch has been updated.

@remyroy remyroy deleted the remyroy:fix-weighted-list-rng branch Dec 19, 2016

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