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ext/Devel-Peek/t/Peek.t - cater for doubledouble where needed #19596

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Apr 8, 2022
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ext/Devel-Peek/t/Peek.t - cater for doubledouble where needed #19596

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43 changes: 37 additions & 6 deletions ext/Devel-Peek/t/Peek.t
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Original file line number Diff line number Diff line change
Expand Up @@ -1550,11 +1550,42 @@ EODUMP
}

{
my $one = 1.0;
my $epsilon_p = 1.0;
$epsilon_p /= 2 while $one != $one + $epsilon_p / 2;
my $epsilon_n = 1.0;
$epsilon_n /= 2 while $one != $one - $epsilon_n / 2;
if($Config{nvtype} eq 'long double' &&
$Config{longdblkind} >= 5 && $Config{longdblkind} <= 8) {
# For this (doubledouble) kind of NV we need to use a separate
# method for assigning values to $epsilon_p and $epsilon_n.
# Theoretically, $epsilon_p should be set to 2 ** -107, and
# $epsilon_n to 2 ** -110. However, a known possible bug in "%.33g"
# formatting will render those values inaccurately, thereby
# incorrectly influencing the results of the "NV 1.0 + epsilon"
# and "NV 1.0 - epsilon" tests. So we test for the presence of
# the bug, and set both of those "epsilon" variables to
# 2 ** -105 if the bug is detected.
# See the discussion at https://github.com/Perl/perl5/issues/19585.

if( sprintf("%.33g", 1.0 + (2 ** -108)) == 1
&&
sprintf("%.33g", 1.0 + (2 ** -107)) > 1 ) {

$epsilon_p = 2 ** -107;
}
else { $epsilon_p = 2 ** -105 } # Avoids the formatting bug.

if( sprintf("%.33g", 1.0 - (2 ** -111)) == 1
&&
sprintf("%.33g", 1.0 - (2 ** -110)) < 1 ) {

$epsilon_n = 2 ** -110;
}
else { $epsilon_n = 2 ** -105 } # Avoids the formatting bug.

}
else {
$epsilon_p /= 2 while 1.0 != 1.0 + $epsilon_p / 2;
$epsilon_n /= 2 while 1.0 != 1.0 - $epsilon_n / 2;
}

my $head = 'SV = NV\($ADDR\) at $ADDR
(?:.+
Expand All @@ -1563,11 +1594,11 @@ EODUMP
(?:.+
)*';

do_test('NV 1.0', $one,
do_test('NV 1.0', 1.0,
$head . 'NV = 1' . $tail);
do_test('NV 1.0 + epsilon', $one + $epsilon_p,
do_test('NV 1.0 + epsilon', 1.0 + $epsilon_p,
$head . 'NV = 1\.00000000\d+' . $tail);
do_test('NV 1.0 - epsilon', $one - $epsilon_p,
do_test('NV 1.0 - epsilon', 1.0 - $epsilon_n,
$head . 'NV = 0\.99999999\d+' . $tail);
}

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