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Search: Posts Made By: cperciva
Forum: Hardware 2003-04-26, 17:39
Replies: 38
Views: 4,659
Posted By cperciva
Given such a fast integer multiply, I wonder if...

Given such a fast integer multiply, I wonder if an integer FFT would end up faster than a floating-point FFT.
Forum: Software 2003-04-16, 17:45
Replies: 11
Views: 753
Posted By cperciva
The Pentium was perfectly *precise*. It just...

The Pentium was perfectly *precise*. It just wasn't *accurate*.
Forum: PrimeNet 2003-04-10, 22:43
Replies: 2
Views: 1,179
Posted By cperciva
Re: DNS questions

Probably the first server cached the old address more recently. DNS updates don't propagate, old values die out.



Probably the first server failed to respond to a request once, so Windows...
Forum: PrimeNet 2003-04-09, 16:53
Replies: 3
Views: 1,102
Posted By cperciva
I doubt prime95 has any vulnerabilities quite...

I doubt prime95 has any vulnerabilities quite that obvious, but history demonstrates that anything not written by DJB is likely to have some security issues... that said, George is a pretty good...
Forum: Lounge 2003-04-06, 14:51
Replies: 19
Views: 1,362
Posted By cperciva
Re: Survey on why you DC.

Which conference?
Forum: Software 2003-03-31, 06:28
Replies: 8
Views: 1,117
Posted By cperciva
No, I'm not an enterprise C++ programmer; I'm a...

No, I'm not an enterprise C++ programmer; I'm a DPhil student at Oxford University, doing my thesis work in parallel computing. I consider the claim that "WinHeap can make multithreaded programs run...
Forum: Software 2003-03-30, 16:06
Replies: 8
Views: 1,117
Posted By cperciva
It's snake oil. Sure, there are cases where it...

It's snake oil. Sure, there are cases where it will be 10 times faster... IF all you do is allocate and release chunks of memory. In other cases, it will be considerably slower than the standard...
Forum: Software 2003-03-25, 18:37
Replies: 37
Views: 2,367
Posted By cperciva
1024 and 24 are not relatively prime. You're...

1024 and 24 are not relatively prime. You're correctly computing 543*123 modulo (1000/24), but since 1000 and 24 share a factor of 8, this only gives you the value modulo 125 instead of modulo 1000.
Forum: Software 2003-03-24, 11:02
Replies: 37
Views: 2,367
Posted By cperciva
You're right; it only works if you can find...

You're right; it only works if you can find appropriate values for a and b. The usefulness comes from the fact that most big numbers we work with are already in that form: Mersenne numbers, Fermat...
Forum: Software 2003-03-21, 03:31
Replies: 37
Views: 2,367
Posted By cperciva
It's worth noting that the "right-angle" FFT for...

It's worth noting that the "right-angle" FFT for multiplying two N bit integers over Z is exactly the same as multiplying modulo 2^N+(-1)i using the DWT I describe in my paper.
Forum: Software 2003-03-12, 20:38
Replies: 37
Views: 2,367
Posted By cperciva
Yes, but people reading my paper and the...

Yes, but people reading my paper and the published version of your paper aren't going to understand that I was referring to an earlier, unpublished, version of your paper.



Well, the constant...
Forum: Software 2003-03-12, 19:40
Replies: 37
Views: 2,367
Posted By cperciva
I feel rather bad, now, about referring to your...

I feel rather bad, now, about referring to your paper (or rather, the estimate contained in it) so roughly... but my comments were entirely accurate when I wrote them. (In fact, I seem to recall...
Forum: Software 2003-03-12, 02:05
Replies: 37
Views: 2,367
Posted By cperciva
http://www.ams.org/journal-getitem?pii=S0025-5718-...

http://www.ams.org/journal-getitem?pii=S0025-5718-02-01419-9

Or, for those of you without a subscription, a preprint is at http://www.sfu.ca/~cperciva/mpaper.ps

I refer to your F24 paper in a...
Forum: Software 2003-03-12, 00:54
Replies: 37
Views: 2,367
Posted By cperciva
It's somewhat more complicated than that; the...

It's somewhat more complicated than that; the (not perfectly accurate) trig data contributes some error, and the error introduced in complex multiplication can be bounded somewhat more closely than a...
Forum: Software 2003-03-11, 23:41
Replies: 37
Views: 2,367
Posted By cperciva
(If anyone hasn't already read it, my paper on...

(If anyone hasn't already read it, my paper on FFT error bounds has *finally* been published in Math. Comp.)
Forum: Software 2003-03-11, 23:35
Replies: 37
Views: 2,367
Posted By cperciva
Ignoring SSE2 which is standard 64-bit FP, the...

Ignoring SSE2 which is standard 64-bit FP, the x86 code does all loads and stores in the 64-bit format. The reason for this is that the 80-bit load and store operations are very slow. Thus, the FFT...
Forum: Software 2003-03-11, 17:59
Replies: 37
Views: 2,367
Posted By cperciva
Yes, but because of the x86's small register set...

Yes, but because of the x86's small register set and the fact that the FFT's we do are so large, this gives only a small accuracy enhancement - perhaps 1-2% over an IEEE64-compliant CPU.
[/quote]
...
Forum: PSearch 2003-02-22, 08:42
Replies: 4
Views: 3,646
Posted By cperciva
Re: largest non-mersenne

If p divides k, then p does not divide k*2^n-1. This means that N=k*2^n-1 is prime with probability k/phi(k) * 1/ln(N) instead of probability 1/ln(N).

For k<100 with k*2^n-1 prime, this moves the...
Forum: Lounge 2003-02-05, 17:43
Replies: 15
Views: 1,066
Posted By cperciva
Personally, I'd say that diabetes research is...

Personally, I'd say that diabetes research is more deserving of support than either AIDS or heart disease -- in the majority of cases, we don't even know the *cause* of type 1 diabetes, let alone how...
Forum: PrimeNet 2003-01-19, 21:52
Replies: 228
Views: 13,538
Posted By cperciva
GIMPS isn't distributed.net. ... which is already...

GIMPS isn't distributed.net. ... which is already insignificant ... ... which is already done by clients.
Forum: PrimeNet 2003-01-19, 20:19
Replies: 228
Views: 13,538
Posted By cperciva
Re: Trying out the forum

Uhh, this may seem impolite, but... who are you? (maybe it's obvious to everyone else, but I'm suffering from both having had wisdom teeth taken out and having had several blood tests taken...
Forum: Math 2003-01-18, 17:46
Replies: 16
Views: 1,577
Posted By cperciva
Richard Brent (who happens to be my DPhil...

Richard Brent (who happens to be my DPhil supervisor) says that he thinks this is the current SNFS record.
Forum: PrimeNet 2003-01-18, 17:44
Replies: 4
Views: 1,233
Posted By cperciva
I'm confused what are we writting this (server)...

I'm confused what are we writting this (server) application in.

Language wise that is.[/quote]

It sounds like it's being written in C and PHP. ;)
Forum: PrimeNet 2003-01-17, 18:54
Replies: 228
Views: 13,538
Posted By cperciva
No. MySQL is an SQL based file system. It isn't...

No. MySQL is an SQL based file system. It isn't a database.

(Of course, databases aren't always necessary, and for such tasks, MySQL performs perfectly well. But I don't think this is such a...
Forum: PrimeNet 2003-01-17, 17:00
Replies: 228
Views: 13,538
Posted By cperciva
Approximately, yes. I must be missing...

Approximately, yes.



I must be missing something here. How would running several servers all the time be cheaper than running one and replacing it if it fails?



The server load should be...
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