On Tuesday, January 8, 2019 at 5:13:12 PM UTC-8, Rob Gaddi wrote:
(snip)
> Nope, I get that too. For any actual physical quantity, 2^64 is utterly
> enormous.
Enormous enough that you wouldn't think that IPv6 would use 128
bit addresses.
I have, from Comcast, 2^68 IP addresses for my home networks.
(So far, I have two subnets with 2^64 each.)
Reply by Eric Jacobsen●January 10, 20192019-01-10
On Tue, 8 Jan 2019 16:37:15 -0800 (PST), gyansorova@gmail.com wrote:
>Somebody check the sums which was fun working out.
>
>I have a sensor which gives out 4096 pulses per revolution. This is attache=
>d to a motor which turns at 1000 rpm. I need to count by using an integer i=
>n increments defined by a signed 64 bit integer. The question is, how long=
> can it count for at this speed before the integer overflows?
>
>64 bits is about + or - 9.23 x10^18 count in one direction only before over=
>flow.
>
>1000 revs/min x 60 min/hr =3D 60,000 revs/hr of the motor.
>
>60,000 revs/hr x 4096 pulses/rev =3D 2.457 x10^8 pulses/hour
>
>There are 24 hrs/day and 365 days/year therefore 8760 hrs/year
>
>Therefore 9.23 x 10^18/2.457 x 10^8 pulses/hour =3D3.767x10^10 hrs to reac=
>h overflow of the counter integer.
>
>This is 4.3 x 10^6 years or 4.3 million years!!
>
>Surely some mistake
>=20
>
There are estimates that there are 10^78 to 10^80 atoms in the
universe.
You can count to ~10^77 with 256 bits, just to get reasonably close.
You can build a 256-bit counter in silicon without too much trouble
and clock it at around 1GHz.
It'd still take 3.67^60 years to count reasonaby close to all the
atoms in the universe with that counter.
This makes a good case for parellelism. ;)
Reply by ●January 9, 20192019-01-09
On Wednesday, January 9, 2019 at 11:43:18 PM UTC+13, Gene Filatov wrote:
> On 09.01.2019 3:37, gyansorova@gmail.com wrote:
> > Somebody check the sums which was fun working out.
> >
> > I have a sensor which gives out 4096 pulses per revolution. This is attached to a motor which turns at 1000 rpm. I need to count by using an integer in increments defined by a signed 64 bit integer. The question is, how long can it count for at this speed before the integer overflows?
> >
> > 64 bits is about + or - 9.23 x10^18 count in one direction only before overflow.
> >
> > 1000 revs/min x 60 min/hr = 60,000 revs/hr of the motor.
> >
> > 60,000 revs/hr x 4096 pulses/rev = 2.457 x10^8 pulses/hour
> >
> > There are 24 hrs/day and 365 days/year therefore 8760 hrs/year
> >
> > Therefore 9.23 x 10^18/2.457 x 10^8 pulses/hour =3.767x10^10 hrs to reach overflow of the counter integer.
> >
> > This is 4.3 x 10^6 years or 4.3 million years!!
> >
> > Surely some mistake
> >
> >
>
> It's extremely helpful that you have written this commentary. If the
> motor fails after some 4.3 million years, we know who to blame.
>
> ^_^
>
> Evgeny.
I think it's great to know that your motor will still be operating after humans are extinct!
Reply by Gene Filatov●January 9, 20192019-01-09
On 09.01.2019 3:37, gyansorova@gmail.com wrote:
> Somebody check the sums which was fun working out.
>
> I have a sensor which gives out 4096 pulses per revolution. This is attached to a motor which turns at 1000 rpm. I need to count by using an integer in increments defined by a signed 64 bit integer. The question is, how long can it count for at this speed before the integer overflows?
>
> 64 bits is about + or - 9.23 x10^18 count in one direction only before overflow.
>
> 1000 revs/min x 60 min/hr = 60,000 revs/hr of the motor.
>
> 60,000 revs/hr x 4096 pulses/rev = 2.457 x10^8 pulses/hour
>
> There are 24 hrs/day and 365 days/year therefore 8760 hrs/year
>
> Therefore 9.23 x 10^18/2.457 x 10^8 pulses/hour =3.767x10^10 hrs to reach overflow of the counter integer.
>
> This is 4.3 x 10^6 years or 4.3 million years!!
>
> Surely some mistake
>
>
It's extremely helpful that you have written this commentary. If the
motor fails after some 4.3 million years, we know who to blame.
^_^
Evgeny.
Reply by Rob Gaddi●January 8, 20192019-01-08
On 1/8/19 4:37 PM, gyansorova@gmail.com wrote:
> Somebody check the sums which was fun working out.
>
> I have a sensor which gives out 4096 pulses per revolution. This is attached to a motor which turns at 1000 rpm. I need to count by using an integer in increments defined by a signed 64 bit integer. The question is, how long can it count for at this speed before the integer overflows?
>
> 64 bits is about + or - 9.23 x10^18 count in one direction only before overflow.
>
> 1000 revs/min x 60 min/hr = 60,000 revs/hr of the motor.
>
> 60,000 revs/hr x 4096 pulses/rev = 2.457 x10^8 pulses/hour
>
> There are 24 hrs/day and 365 days/year therefore 8760 hrs/year
>
> Therefore 9.23 x 10^18/2.457 x 10^8 pulses/hour =3.767x10^10 hrs to reach overflow of the counter integer.
>
> This is 4.3 x 10^6 years or 4.3 million years!!
>
> Surely some mistake
>
>
Nope, I get that too. For any actual physical quantity, 2^64 is utterly
enormous.
--
Rob Gaddi, Highland Technology -- www.highlandtechnology.com
Email address domain is currently out of order. See above to fix.
Reply by ●January 8, 20192019-01-08
Somebody check the sums which was fun working out.
I have a sensor which gives out 4096 pulses per revolution. This is attached to a motor which turns at 1000 rpm. I need to count by using an integer in increments defined by a signed 64 bit integer. The question is, how long can it count for at this speed before the integer overflows?
64 bits is about + or - 9.23 x10^18 count in one direction only before overflow.
1000 revs/min x 60 min/hr = 60,000 revs/hr of the motor.
60,000 revs/hr x 4096 pulses/rev = 2.457 x10^8 pulses/hour
There are 24 hrs/day and 365 days/year therefore 8760 hrs/year
Therefore 9.23 x 10^18/2.457 x 10^8 pulses/hour =3.767x10^10 hrs to reach overflow of the counter integer.
This is 4.3 x 10^6 years or 4.3 million years!!
Surely some mistake