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-   -   1cpu vs 2cpu (https://www.mersenneforum.org/showthread.php?t=26360)

 cardmaker 2020-12-31 11:08

1cpu vs 2cpu

hello, im testing new hardware factoring a 100digit and no much diference make between 1 cpu vs 2 cpu only 30sec does it normal?
is the same number and same bin(script 0.84 , msieve 1.52), only the change is the number os cores.
NUM_CORES = 12
to
NUM_CORES = 24

and the result whit 1 cpu:
[QUOTE]Number: example
N = 1522605027922533360535618378132637429718068114961380688657908494580122963258952897654000350692006139 (100 digits)
Divisors found:
r1=37975227936943673922808872755445627854565536638199 (pp50)
r2=40094690950920881030683735292761468389214899724061 (pp50)
Version: Msieve v. 1.52 (SVN Nicht versioniertes Verzeichnis)
Total time: 0.21 hours.
Factorization parameters were as follows:
n: 1522605027922533360535618378132637429718068114961380688657908494580122963258952897654000350692006139
# norm 1.402930e-13 alpha -6.325236 e 1.281e-08 rroots 2
skew: 3483965.44
c0: -36738379143255767765564663397
c1: 75967609570279467412754
c2: -784169456850679
c3: -3486221646
c4: 1368
Y0: -1027140279095180418809608
Y1: 16592488498117
type: gnfs
Factor base limits: 1800000/1800000
Large primes per side: 3
Large prime bits: 26/26
Sieved algebraic special-q in [0, 0)
Total raw relations: 5073376
Relations: 254576 relations
Pruned matrix : 155741 x 155971
Polynomial selection time: 0.01 hours.
Total sieving time: 0.17 hours.
Total relation processing time: 0.01 hours.
Matrix solve time: 0.02 hours.
time per square root: 0.00 hours.
Prototype def-par.txt line would be: gnfs,99,4,58,1500,0.003,0.4,220,15,10000,2000,1800000,1800000,26,26,48,48,2.5,2.5,100000
total time: 0.21 hours.
x86_64
processors: 48, speed: 1.20GHz
Linux-4.4.0-197-generic-x86_64-with-Ubuntu-16.04-xenial
Running Python 2.7
[/QUOTE]

and whit 2 cpu:
[QUOTE]Number: example
N = 1522605027922533360535618378132637429718068114961380688657908494580122963258952897654000350692006139 (100 digits)
Divisors found:
r1=37975227936943673922808872755445627854565536638199 (pp50)
r2=40094690950920881030683735292761468389214899724061 (pp50)
Version: Msieve v. 1.52 (SVN Nicht versioniertes Verzeichnis)
Total time: 0.20 hours.
Factorization parameters were as follows:
n: 1522605027922533360535618378132637429718068114961380688657908494580122963258952897654000350692006139
# norm 9.462249e-14 alpha -4.664878 e 1.057e-08 rroots 4
skew: 3782058.60
c0: 35793799656782527909425094900
c1: -19487356755197005852048
c2: -28534739231977525
c3: 3449886256
c4: 804
Y0: -1173089344615252621251927
Y1: 4312706706875
type: gnfs
Factor base limits: 1800000/1800000
Large primes per side: 3
Large prime bits: 26/26
Sieved algebraic special-q in [0, 0)
Total raw relations: 5021071
Relations: 284824 relations
Pruned matrix : 173370 x 173598
Polynomial selection time: 0.00 hours.
Total sieving time: 0.16 hours.
Total relation processing time: 0.01 hours.
Matrix solve time: 0.03 hours.
time per square root: 0.01 hours.
Prototype def-par.txt line would be: gnfs,99,4,58,1500,0.003,0.4,220,15,10000,2000,1800000,1800000,26,26,48,48,2.5,2.5,100000
total time: 0.20 hours.
x86_64
processors: 48, speed: 1.20GHz
Linux-4.4.0-197-generic-x86_64-with-Ubuntu-16.04-xenial
Running Python 2.7
[/QUOTE]

by the clock wall only 30sec of diference for factorization does it normal? sould it be more diference whit 2 cpu?
also this line "processors: 48, speed: 1.20GHz" is not right because my cpu clock is 2.3GHZ and not 1.2 anyone have an ideia?

 retina 2020-12-31 11:24

Both results say the exact same CPU count:[code]processors: 48, speed: 1.20GHz[/code]So I would expect them to finish in a similar time.

 EdH 2020-12-31 13:34

The speed is a "right now" speed rather than a listed speed. The 30 second difference is probably due to the polynomial rather than the hardware.

What was the command line that invoked msieve? Did it include "-t <number of threads to use>"? If msieve was called from another program/script, does that p/s provide the hardware values to use?

 cardmaker 2020-12-31 16:07

@retina
[QUOTE]processors: 48, speed: 1.20GHz[/QUOTE]
this line i think is a reading of system not the total cores i set in script, because when executing script only the number of thread i set in script are executed.
example when set to 12 log appear t0 -> t23
when set 24 log appear t0 ->47

@EdH
yes the number of thread are invoked correctly in the msieve comand line.
i use the script version 84, and i see its correct.

 charybdis 2020-12-31 16:48

Setting
[QUOTE=cardmaker;567816]
NUM_CORES = 12