View Single Post
Old 2002-09-18, 04:57   #8
dswanson
 
dswanson's Avatar
 
Aug 2002

C816 Posts
Default

As promised, here are the results for 8904871.

First, the processor and version number data...
[code:1]Intel(R) Pentium(R) 4 CPU 1.80GHz
CPU speed: 1807.56 MHz
CPU features: RDTSC, CMOV, PREFETCH, MMX, SSE, SSE2
L1 cache size: 8 KB
L2 cache size: 512 KB
L1 cache line size: 64 bytes
L2 cache line size: 64 bytes
TLBS: 64
Prime95 version 22.8, RdtscTiming=1
[/code:1]

And the results, cut-and-paste from the results file (edited heavily for brevity). Things started relatively quietly, with only 2 errors in the first 5.4M...
[code:1][Fri Sep 13 18:33:37 2002]
Trying 1000 iterations for exponent 8904871 using 448K FFT.
If average roundoff error is above 0.2414, then a larger FFT will be used.
Final average roundoff error is 0.23979, using 448K FFT for exponent 8904871.

[Sat Sep 14 04:30:30 2002]
Iteration: 1276787/8904871, ERROR: ROUND OFF (0.40625) > 0.40
Continuing from last save file.
Disregard last error. Result is reproducible and thus not a hardware problem.
For added safety, redoing iteration using a slower, more reliable method.
Continuing from last save file.

[Sun Sep 15 00:26:09 2002]
Iteration: 3822131/8904871, ERROR: ROUND OFF (0.40625) > 0.40
Continuing from last save file.
Disregard last error. Result is reproducible and thus not a hardware problem.
For added safety, redoing iteration using a slower, more reliable method.
Continuing from last save file.[/code:1]
But then it got really exciting for the next 1.2M...
[code:1]Iteration: 5455889/8904871, ERROR: ROUND OFF (0.40625) > 0.40
Iteration: 5575813/8904871, ERROR: ROUND OFF (0.40625) > 0.40
Iteration: 5629431/8904871, ERROR: ROUND OFF (0.40625) > 0.40
Iteration: 5994211/8904871, ERROR: ROUND OFF (0.4375) > 0.40
Iteration: 6175814/8904871, ERROR: ROUND OFF (0.40625) > 0.40
Iteration: 6380548/8904871, ERROR: ROUND OFF (0.40625) > 0.40
Iteration: 6558839/8904871, ERROR: ROUND OFF (0.40625) > 0.40[/code:1]
Then quieted back down for the final 2.3M...
[code:1]Iteration: 7548466/8904871, ERROR: ROUND OFF (0.40625) > 0.40
Iteration: 8640014/8904871, ERROR: ROUND OFF (0.40625) > 0.40

[Mon Sep 16 16:39:44 2002]
UID: dswanson/pc1800B, M8904871 is not prime. Res64: 7563B6330A3BDDC0. WY1: F5DFC11B,519163,0B000B00
[/code:1]
Total: 11 roundoff errors in 8.9M, pretty close to George and Brian's goal of 1 per million. But, as should be expected for a random-ish process, the errors were certainly NOT uniformly distributed!

George, how can I find out if my residual matches that from the first run of this number? Of course, given that this number was available only because its first run also had errors reported, a negative answer is probable and only means I'll have to wait for the triple-check (or possibly quadruple-check, if both mine and the previous run are bad) to know for sure.
dswanson is offline   Reply With Quote