ST_TileEnvelope test failure in 32 bit

[Algunenano]

I?m seeing a test failure for ST_TileEnvelope regress in 32bit (ubuntu-bionic-i386):

 regress .. failed (diff expected obtained: /tmp/pgis_reg/test_68_diff)
-----------------------------------------------------------------------------
--- regress_expected	2020-01-10 15:21:10.000000000 +0000
+++ /tmp/pgis_reg/test_68_out	2020-01-14 11:20:15.448620010 +0000
@@ -197,7 +197,7 @@
 ERROR:  ST_TileEnvelope: Invalid tile zoom value, -1
 ERROR:  ST_TileEnvelope: Invalid tile y value, 1
 229|SRID=3857;POLYGON((-20037508.342789 -20037508.342789,-20037508.342789 20037508.342789,20037508.342789 20037508.342789,20037508.342789 -20037508.342789,-20037508.342789 -20037508.342789))
-230|SRID=3857;POLYGON((0 -2504688.54284862,0 0,2504688.54284862 0,2504688.54284862 -2504688.54284862,0 -2504688.54284862))
+230|SRID=3857;POLYGON((0 -2504688.54284863,0 0,2504688.54284863 0,2504688.54284863 -2504688.54284863,0 -2504688.54284863))
 231|SRID=3857;POLYGON((17532819.7999404 -20037508.342789,17532819.7999404 -17532819.7999404,20037508.342789 -17532819.7999404,20037508.342789 -20037508.342789,17532819.7999404 -20037508.342789))
 232|POLYGON((0 -12.5,0 0,12.5 0,12.5 -12.5,0 -12.5))
 233|POLYGON((87.5 -100,87.5 -87.5,100 -87.5,100 -100,87.5 -100))
-----------------------------------------------------------------------------

I changed the function to calculate the input bbox (instead of using the one serialized, since that one uses 32b and that was too imprecise for the default use case) in #4600, which affected this output.

[Algunenano]

I tried reordering the floating point operations to see if doing first the operations in closer to zero gave any better result but it didn't work, so I'll simply reduce the number of decimals in that test and move on.

PR: ​https://github.com/postgis/postgis/pull/534

[Raúl Marín <git@…>]

In b73f673/git:

Reduce output precision in ST_TileEnvelope test

The output is slightly different in 32bit plaftorms

References #4619
References #4600

[Raúl Marín <git@…>]

In 3c069bf7/git:

Reduce output precision in ST_TileEnvelope test

The output is slightly different in 32bit plaftorms

Closes #4619
Closes ​https://github.com/postgis/postgis/pull/534