Re: [PATCH] Improve geometric types

On 08/03/2018 02:39 PM, Tomas Vondra wrote:
> On 08/03/2018 06:40 AM, Kyotaro HORIGUCHI wrote:
>> ...
>>
>> I'm not confident on replacing double to float8 partially in gist
>> code. After the 0002 patch applied, I see most of problematic
>> usage of double or bare arithmetic on dimentional values in
>> gistproc.c.
>>
>>> static inline float
>>> non_negative(float val)
>>> {
>>>     if (val >= 0.0f)
>>>         return val;
>>>     else
>>>         return 0.0f;
>>> }
>>
>> It is used as "non_negative(overlap)", where overlap is float4,
>> which is calculated using float8_mi.  Float4 makes sense only if
>> we need to store a large number of it to somewhere but they are
>> just working varialbles. Couldn't we eliminate float4 that
>> doesn't have a requirement to do so?
>>
>
> I'm not sure I follow. The patch does not modify non_negative() at all,
> and we still call it like this:
>
>     if (non_negative(overlap) < non_negative(context->overlap) ||
>         (range > context->range &&
>          non_negative(overlap) <= non_negative(context->overlap)))
>         selectthis = true;
>
> where all the "overlap" values are still float4. The only thing that
> changed here is that instead of doing the arithmetic operations directly
> we call float8_mi/float8_div to benefit from the float8 handling.
>
> So I'm not sure how does the patch beaks this? And what do you mean by
> 'eliminate float4'?
>

Kyotaro-san, can you explain what your concerns regarding this bit are?
I'd like to get 0002 committed, but I'm not sure I understand your point
about the changes in gist code, so I can't address them. And I certainly
don't want to just ignore them ...

regards

--
Tomas Vondra http://www.2ndQuadrant.com
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