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113 lines
3.6 KiB
113 lines
3.6 KiB
# ==== Purpose ====
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#
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# Generate a random number in such a way that the sequence of numbers
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# generated by successive calls can be deterministic.
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#
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# ==== Usage ====
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#
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# --let $rand_type= { int | float | decide | init }
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# [--let $rand_min= MIN_VALUE]
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# [--let $rand_max= MAX_VALUE]
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# [--let $rand_probability= THRESHOLD]
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# [--let $rand_seed= SEED]
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# --source include/rand.inc
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# --echo Random number: $rand
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#
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# Parameters:
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#
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# $rand_type
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# If set to 'int', generates an integer in the range
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# [$rand_min, $rand_max).
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#
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# If set to 'float', generates a floating point number in the
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# range [$rand_min, $rand_max).
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#
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# If set to 'decide', generates 1 with probability
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# $rand_probability and 0 with probability 1-$rand_probability.
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#
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# If set to 'init', does not generate $rand, but initializes
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# the $rand_seed in case this is the first invocation.
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#
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# $rand_min, $rand_max
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# Range of values for $rand_type=int or $rand_type=float.
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# These are evaluated in an SQL query, so may contain valid
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# arithmetic operations.
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#
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# $rand_probability
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# Probability to get a '1' if $rand_type=decide.
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# This is evaluated in an SQL query, so may contain valid
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# arithmetic operations.
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#
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# $rand_seed
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# The seed value. If you want to set the seed to a random number
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# that is different for each invokation of the test, set
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# $rand_seed to the empty string. Normally, $rand_seed is only
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# read in the first invokation of rand.inc. If you want to reset
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# the seed later, set $_rand_state to the empty string.
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#
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# ==== Implementation ====
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#
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# This RNG uses the following multiply-with-carry algorithm:
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# int32 z, w;
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# if (z == 0) z = 1;
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# if (w == 0) w = 1;
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# z = 36969 * (z & 65535) + (z >> 16);
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# w = 18000 * (w & 65535) + (w >> 16);
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# rand = (z << 16) + w;
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# In this implementation, z is stored in the low 32 bits and w in the
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# high 32 bits of $_rand_state.
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--let $_maxint32= ((1 << 32) - 1)
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if ($_rand_state == '')
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{
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if ($rand_seed == '')
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{
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--let $rand_seed= `SELECT FLOOR(RAND() * (1 << 63))`
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}
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--let $write_var= $rand_seed
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--let $write_to_file= $MYSQLTEST_VARDIR/tmp/rand_seed
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--source include/write_var_to_file.inc
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--let $_rand_state= $rand_seed
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--let $_rand_lo= IF(($_rand_state) & $_maxint32 = 0, 1, ($_rand_state) & $_maxint32)
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--let $_rand_hi= IF(($_rand_state) >> 32 = 0, 1, ($_rand_state) >> 32)
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--let $_rand_state= `SELECT ((36969 * $_rand_lo + ($_rand_lo >> 16)) & $_maxint32) + (((18000 * ($_rand_hi & 65535) + ($_rand_hi >> 16)) & $_maxint32) << 32)`
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}
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--let $_rand_lo= IF(($_rand_state) & $_maxint32 = 0, 1, ($_rand_state) & $_maxint32)
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--let $_rand_hi= IF(($_rand_state) >> 32 = 0, 1, ($_rand_state) >> 32)
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--let $_rand_state= `SELECT ((36969 * $_rand_lo + ($_rand_lo >> 16)) & $_maxint32) + (((18000 * ($_rand_hi & 65535) + ($_rand_hi >> 16)) & $_maxint32) << 32)`
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--let $rand= ((($_rand_state << 16) + ($_rand_state >> 32)) & $_maxint32)
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if ($rand_type == decide)
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{
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--let $_rand_probability= 0.5
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if ($rand_probability != '')
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{
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--let $_rand_probability= $rand_probability
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}
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--let $rand= `SELECT IF($rand / (1 << 32) < ($rand_probability), 1, 0)`
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}
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if ($rand_type != decide)
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{
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--let $_rand_min= 0
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if ($rand_min)
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{
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--let $_rand_min= $rand_min
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}
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--let $_rand_max= 1
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if ($rand_max)
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{
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--let $_rand_max= $rand_max
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}
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if ($rand_type == int)
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{
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--let $rand= `SELECT ($_rand_min) + ($rand % (($_rand_max) - ($_rand_min)))`
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}
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if ($rand_type == float)
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{
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--let $rand= `SELECT ($_rand_min) + ($rand * (($_rand_max) - ($_rand_min)) / (1 << 32))`
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}
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}
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--error 0,1
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--remove_file $MYSQLTEST_VARDIR/tmp/rand_seed
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