Problem with Math.random()

MostafaGamal

That's true.
i agree with you.

but for some reasons .. i can't move on the C++ side for now.

but as u said, it is a JS command, so ... is there a missing dependency or OS package that needs to be installed 1st to let JS works well in QT ?

maybe there is some QT versions that has a problems with JS ? if so .. which recommended version of QT shall i install alongside QT Creator version ?

JKSH

@MostafaGamal said in Problem with Math.random():

need a logical reason for not being work correctly for just upgrading my OS !

There are many possibilities.

Do you have an AMD Ryzen CPU? Some models and BIOS versions have faulty random number generators (RNGs): https://forum.manjaro.org/t/i-get-a-cpu-random-generator-warning-advising-me-to-disable-hardware-random-number-generation/116796

Try updating your BIOS
Run some tests using rng-tools: https://wiki.archlinux.org/index.php/Rng-tools (the article is for Arch Linux but the same tools exist in Ubuntu repos)

J.Hilk

@MostafaGamal said in Problem with Math.random():

but for some reasons .. i can't move on the C++ side for now.

you should really consider it, because you're reinventing the wheel ;)

Qt has a nice and easy to use QUuid class
simply wrap it in a basic class and expose it to QML and import it where you need it.

MostafaGamal

@JKSH
Yes, i have the same processor as in the forum post : AMD Ryzen 7 3700X 8-Core @ 16x 3.6GHz
if updating BIOS is the solution ... which BIOS version shall i install ? (My MotherBoard is : Gigabyte B450 Aorus Pro Wifi)

also installed rng-tools for testing.
that was the output of command

rngtest -c 1000 </dev/random

rngtest 5
Copyright (c) 2004 by Henrique de Moraes Holschuh
This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

rngtest: starting FIPS tests...
rngtest: bits received from input: 20000032
rngtest: FIPS 140-2 successes: 999
rngtest: FIPS 140-2 failures: 1
rngtest: FIPS 140-2(2001-10-10) Monobit: 0
rngtest: FIPS 140-2(2001-10-10) Poker: 0
rngtest: FIPS 140-2(2001-10-10) Runs: 1
rngtest: FIPS 140-2(2001-10-10) Long run: 0
rngtest: FIPS 140-2(2001-10-10) Continuous run: 0
rngtest: input channel speed: (min=263.549; avg=252860.427; max=6493506.494)bits/s
rngtest: FIPS tests speed: (min=45.960; avg=84.689; max=87.094)Mibits/s
rngtest: Program run time: 79320378 microseconds

also tried this command : sudo rngd -f

and the output was:
too many FIPS failures, disabling entropy source

too many FIPS failures, disabling entropy source

No entropy sources working, exiting rngd

so .. do i have a CPU Problem ? and how do Math.random() work ? does it depend on hardware rnd ? or a kernel /dev/random ?

JKSH

@MostafaGamal said in Problem with Math.random():

Yes, i have the same processor as in the forum post : AMD Ryzen 7 3700X 8-Core @ 16x 3.6GHz
if updating BIOS is the solution ... which BIOS version shall i install ? (My MotherBoard is : Gigabyte B450 Aorus Pro Wifi)

Get the latest version from your motherboard's support website.

so .. do i have a CPU Problem ?

Probably, since it's not providing entropy.

and how do Math.random() work ? does it depend on hardware rnd ? or a kernel /dev/random ?

I don't know the internal details, but good modern RNGs should always depend on hardware.

MostafaGamal

@J-Hilk
sure.

taking this into consideration.

Thanks a lot :))

MostafaGamal

@JKSH

i've tried to run

quint32 rnd = QRandomGenerator::global()->generate();

in a seperate new project for testing too and found the following:
rnd value is always constant : 1988610280

i think It leaves no doubt that it is CPU issue .. right ?

fcarney

@MostafaGamal said in Problem with Math.random():

quint32 rnd = QRandomGenerator::global()->generate();

Did you run it more than once during the same run? Did you specify a seed value? What seed value?

MostafaGamal

@fcarney
no i didn't provide a seed value.

but i ran it more than once, Yes about 9 times
and the same value every time.

btw .. when tracing my UUID Function a new number is generated every 58 tick.

for ex: if i did a for loop 58 times, a new value is generated.

fcarney

@MostafaGamal said in Problem with Math.random():

but i ran it more than once, Yes about 9 times

That is not what I asked:

for(int count=0; count<10; ++count){
    quint32 rnd = QRandomGenerator::global()->generate();
    qInfo() << rnd;
}

Does this produce the same output for all 10 values?

Edit:
I get completely different values on every run. So yeah, there is something wrong. I am also not providing a seed.

MostafaGamal

@fcarney

Yes,
The same output every run without a seed.

so, yeah something is not correct here. i'll update my BIOS then re-check it again

fcarney

@MostafaGamal You have found a really interesting and annoying problem. Please keep us posted as to the outcome.

MostafaGamal

The problem is fixed after updating my BIOS Successfully which updated AGESA to version 1.0.0.3 ABBA

@fcarney Yes, it is very annoying one!

Thanks Everyone for helping me :))

Special Thanks to @JKSH as he mentioned that the problem is a hardware issue not software one.