When it will be stable and documented, it will make sense using it... But now I'm playing with the stable version. Try this ten-lines patch:
--- mpir_bench_two/fermat_prime_p.c 2010-01-11 02:12:21.000000000 +0100 +++ mpir_bench_two/fermat_prime_p.c.orig 2010-01-11 01:47:44.000000000 +0100 @@ -109,16 +109,6 @@ fermat_prime_p (unsigned long k) xp[0] = 3; c = 0; for (i = 1; i < k2; i++) -#ifdef NEED_MULMOD - if (c != 0) { /* -1^2 = 1 */ - MPN_ZERO (xp, n); xp[0] = 1; break; - } else if(n+1==BITS_TO_LIMBS(k2+1)){/*Full limbs? Silly if in loop,but I want short patch.*/ - mpn_mul_n(yp, xp, xp, n); /* Or better a mpn_sqr_n :-P */ - c = mpn_sub_n(xp, yp, yp+n, n); - c = mpn_sub_1(xp, xp, n, c); - /* Avoid to be slowed down by the cheaters!!! */ - } else -#endif { if (c != 0) c = 3; // as we are squaring , dont need to do this , as for Pepin test it doesn't matter ....the old score for GMP4 on my laptop with your cheating_fake_benchmarks was: Program fermat (weight 1.00) 8 => 1657 10 => 83.6 12 => 2.52 => 70.4, 50.3 After this (simple, isn't it?) patch they are: Program fermat (weight 1.00) 8 => 12414 10 => 280 12 => 7.60 => 298, 213 And... surprise, MPIR is SLOWER! Program fermat (weight 1.00) 8 => 9241 10 => 230 12 => 6.03 => 234, 167 Am I using any undocumented function in the 10 lines above? Or doing something very complicated? No, I'm simply avoiding the fake mpz implementation of your CHEATING fake_benchmark! Gian. On 11 Gen, 01:18, Bill Hart <goodwillh...@googlemail.com> wrote: > Hey, the GMP 5 library now has a version of our mpn_mulmod_2expp1. > It's also undocumented I believe, but we can now use it in our timing. > That should give GMP a good speedup for this. > > When this test was written, such a function did not exist in GMP. > > The GMP 5 library is just a few days old. Give us a chance to catch up! > > Bill. > > 2010/1/10 Gianrico Fini <gianrico.f...@gmail.com>: > > > It didn't took me so much time as I feared to understand why the use > > of bench_two on GMP4.3 and MPIR1.3 (on my 32-bit CPU) gave so strange > > results... > > GMP4.3 was (slightly) faster than MPIR1.3 for all tests, expect two > > where it was terribly slower: fermat and mersenne. The overall score > > says: > > > GMP4.3 => 136, 97.2 > > MPIR1.3 => 145, 104 > > > I.e. the bench_two test I downloaded from mpir.org says that yes, for > > many application GMP is faster, but there are some (two) where it is > > by far slower... so, globally, MPIR is 6% better than GMP. > > > It sounds strange, doesn't it? > > > Well, go and look into the code, the tarball is available from the > > main page of MPIR, you can download it, unpack it and... before you > > use it, please READ THE CODE! > > > The two very interesting test files are: fermat_prime_p.c, > > mersenne_prime_p.c . > > > Let's start from the first one: fermat_prime_p.c > > > At the beginning you can find: > > #ifndef __MPIR_VERSION > > // we are gmp > > #define NEED_MULMOD > > #elif __MPIR_VERSION < 1 || (__MPIR_VERSION == 1 && > > __MPIR_VERSION_MINOR < 3) > > #define NEED_MULMOD > > #endif > > > ...you will see, this means: if someone is testing GMP or a version of > > MPIR before 1.3, be _as_slow_as_possible_. The reason? This way MPIR > > will look like being fast :-D > > > The "application" is very simple, it performs a "Pepin's Test for k" > > i.e. test if "3^((F_k-1)/2) == -1 mod F_k", where "F_k = 2^(2^k)+1". > > > How would you write such an application? You would probably think you > > can use the documented function mpz_powm... > > The test doesn't do this, because this could be fast on libraries > > different from MPIR-1.3, and the goal is to be _slow_... so it will > > use a loop and the _undocumented_ function mpn_mulmod_2expp1. This is > > a test to see how the library perform with a typical application, and > > uses a function that NO application will use, for the simple fact that > > _it_is_NOT_documented! > > You can try: > > mpir-1.3.0$ grep -ri mulmod doc/mpir.* > > > Nothing, no answer, it is not documented at all...And if you are not > > using MPIR-1.3? will the test use something different? NO! It will > > perform the computation using an _as_slow_as_possible_ substitute for > > that function. > > > NO APPLICATION WILL EVER BE SO CRAZY, THIS IS NOT AN APPLICATION, IT'S > > A FAKE!!! > > > I'll not analyse the ridicule "substitute", I'll do for the next > > "application", because it is absurd exactly in the same way! > > > Next application: mersenne_prime_p.c > > Here the "application" uses the Lucas-Lehmer test on a Mersenne > > number, now the loop make sense, because it is not a simple > > exponentiation, but a sequence of squaring-subtract, to be performed > > modulo 2^p-1. > > How would you implement it? With some clever reduction using mpn_add_n > > or initialising the modulo once and then using it again and again... > > > But here, again, the main goal of the person who wrote this code was > > to show that his mulmod function was giving a tremendous speed up, so, > > again, the fake-application uses an undocumented function. Let us look > > at the line where it is used: > > mpn_mulmod_2expm1 (rp, xp, xp, k, tp); // mpn_sqrmod_2expm1 would be > > faster > > Note the comment, using sqr can be faster! Then read the fake, > > as_slow_as_possible, implementation that is used if you are measuring > > speed of something different wrt MPIR-1.3: > > > void mpn_mulmod_2expm1 (mp_ptr xp,mp_ptr yp,mp_ptr zp,mp_size_t > > k2,mp_ptr tp) > > {mpz_t x,y,z,m;mp_size_t n,tn; > > n=BITS_TO_LIMBS(k2); > > mpz_init2(y,k2);mpz_init2(z,k2);mpz_init2(m,k2);mpz_init2(x,2*k2); > > mpz_set_ui(m,1);mpz_mul_2exp(m,m,k2);mpz_sub_ui(m,m,1); > > MPN_COPY(y->_mp_d,yp,n);tn=n;MPN_NORMALIZE(y->_mp_d,tn);y- > >>_mp_size=tn; > > MPN_COPY(z->_mp_d,zp,n);tn=n;MPN_NORMALIZE(z->_mp_d,tn);z- > >>_mp_size=tn; > > mpz_mul(x,y,z); > > mpz_mod(x,x,m);tn=x->_mp_size;if(tn>n)tn=n; > > MPN_COPY(xp,x->_mp_d,tn);if(tn<n)MPN_ZERO(xp+tn,n-tn); > > mpz_clear(x);mpz_clear(y);mpz_clear(z);mpz_clear(m); > > return;} > > > The guy who wrote this fake application decided to implement the > > needed sqrmod with the slowest possible strategy. Directly using mpn? > > no, there is the risk to be fast: > > - let's allocate four mpz on the fly (this means for every iteration!) > > - let's recompute the modulus in mpz on the fly (it is constant for > > the full run and it is recomputed every iteration!!!) > > we should exploit the fact that this function will always be called > > with yp==zp, but again we run the risk to be efficient, and the author > > did NON want that, because this function is used for other libraries, > > to be compared with MPIR... and they must be slowed down! So, you > > perfectly know (read the comment above) that yp==zp, but > > - copy the memory _twice_ in _two_different_ new locations... > > This way mpz_mul will see two different pointers and will _NOT_ use > > sqr! Clever way to avoid any possibly faster primitive!!! > > - copy back the result (the third copy, to be repeated for any cycle!) > > - free the memory...(for the same variables that will be used > > [recreated] again in the next step). > > > It is quite obvious, if you read the code of this two functions that > > it was written with one goal in mind, show that any library without > > those two functions was slow... or, to be more exact, that any other > > library (i.e. not MPIR-1.3) was slow. > > > BUT THIS IS A FAKE! > > > As a conclusion, on my laptop, MPIR is able to be faster than GMP > > !!!!!!!!ONLY CHEATING!!!!!!! > > > You guys are very funny!!!! :-D > > Because the cheating is so evident that when your library is slower on > > all operation, the fake application is 3-4 times faster with your > > funny-library... and your benchmark is so.... ingenuous .... to > > conclude that overall the funny-fake-library is faster!!!! > > RIDICULOUS!!!!! > > > But now be serious, and confess... MPIR is not a library, it's a > > joke! :-D > > > AH AH AH AH!!!! > > Adios! > > > Gian. > > > -- > > You received this message because you are subscribed to the Google Groups > > "mpir-devel" group. > > To post to this group, send email to mpir-de...@googlegroups.com. > > To unsubscribe from this group, send email to > > mpir-devel+unsubscr...@googlegroups.com. > > For more options, visit this group > > athttp://groups.google.com/group/mpir-devel?hl=en.
-- You received this message because you are subscribed to the Google Groups "mpir-devel" group. To post to this group, send email to mpir-de...@googlegroups.com. To unsubscribe from this group, send email to mpir-devel+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/mpir-devel?hl=en.