'setprecision', 24
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Beat Aebischer
il 21 Gen 2021
Commentato: Beat Aebischer
il 26 Gen 2021
Why are the two results below the same? I would like to simulate single precision with system_dependent('setprecision' , 24).
>> system_dependent('setprecision', 64)
>> 10000*sqrt(exp(pi))-48104
ans =
0.773809653510398
>> system_dependent('setprecision', 24)
>> 10000*sqrt(exp(pi))-48104
ans =
0.773809653510398
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Walter Roberson
il 25 Gen 2021
system_dependent('setprecision')... I seem to recall that it only ever had effect on windows and only for some of the older releases. You could find more information on Yair's undocumented-matlab site.
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Gaurav Garg
il 25 Gen 2021
Hi,
On running the same code, and then verifying the variable precision being used, I could see that the variable precision was never changed.
You can verify the variable precision using the digits.
digits
In your case, if you need to change the precision, you can use the below piece of code -
digitsOld = digits(64);
vpa(10000*sqrt(exp(pi))-48104)
digits
digitsOld = digits(24);
vpa(10000*sqrt(exp(pi))-48104)
digits
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Walter Roberson
il 25 Gen 2021
The solution with vpa needs modification to prevent the argument from being evaluated in double precision before it gets to vpa.
Q = @(v) sym(v) ;
digitsOld = digits(64);
vpa(10000*sqrt(exp(Q(pi)))-48104)
digits
digitsOld = digits(24);
vpa(10000*sqrt(exp(Q(pi)))-48104)
It would need further modifications to emulate step by step evaluation at the chosen digits the way that setting system_dependent('precision') would
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