test/fpconv1.test

# 2023-07-03
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
# 
# This file contains a test that attempts to verify the claim that the
# floatpoint-to-text conversion routines built into SQLite maintain at
# least 15 significant digits of accuracy.
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl

if {[catch {load_static_extension db decimal} error]} {
  puts "Skipping decimal tests, hit load error: $error"
  finish_test; return
}

sqlite3_create_function db
do_execsql_test fpconv1-1.0 {
  WITH RECURSIVE
       /* Number of random floating-point values to try.
       ** On a circa 2016 x64 linux box, this test runs at
       ** about 80000 cases per second  -------------------vvvvvv */
    c(x) AS (VALUES(1) UNION ALL SELECT x+1 FROM c WHERE x<100000),
    fp(y) AS MATERIALIZED (
       SELECT CAST( format('%+d.%019d0e%+03d',
                           random()%10,abs(random()),random()%200) AS real)
        FROM c
    )
  SELECT y FROM fp
   WHERE -log10(abs(decimal_sub(dtostr(y,24),format('%!.24e',y))/y))<15.0;
                     /* Number of digits of accuracy required -------^^^^ */
} {}
#  ^---- Expect a empty set as the result.  The output is all tested numbers
#        that fail to preserve at least 15 significant digits of accuracy.

finish_test