Marc B. Reynolds Marc-B-Reynolds
Marc-B-Reynolds
/ tanpi.c
Created
May 10, 2020 07:24
hacky scalar branch-free tanpi (not intended for use)
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| // Public Domain under http://unlicense.org, see link for details. | |
| #include <stdint.h> | |
| #include <stdlib.h> | |
| #include <stdio.h> | |
| #include <math.h> | |
| #include <string.h> | |
| #include "xmmintrin.h" | |
| #include "wmmintrin.h" |
Marc-B-Reynolds
/ gist:8cd39e23e09d78b6f678d7d0214dcfe7
Last active
April 6, 2020 12:49
MathJax 2 vs. 3 hack
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| {% if page.mathjax3 %} | |
| <script> | |
| window.MathJax = { | |
| options: { | |
| menuOptions: { | |
| settings: { | |
| zoom: "None", | |
| zscale: "150%" | |
| } |
Marc-B-Reynolds
/ approx.sollya
Last active
January 27, 2021 22:26
sollya script and output for sincospi in both single and double precision
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| /* -*- mode: c; -*- */ | |
| // create primary range approximations of sin(pi x) and cos(pi x) for x on [-1/4,1/4] | |
| // both for single and double precision | |
| R = [0;1/4]; | |
| T = floating; | |
| E = relative; | |
| B = [|24...|]; |
Marc-B-Reynolds
/ test.c
Created
July 6, 2019 22:26
testu01 rabbit driver for https://lemire.me/blog/2019/07/03/a-fast-16-bit-random-number-generator/
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| #include <inttypes.h> | |
| #include <stdio.h> | |
| #include <stdint.h> | |
| #include "gdef.h" | |
| #include "swrite.h" | |
| #include "bbattery.h" | |
| #include "scomp.h" | |
| #include "swalk.h" | |
| #include "svaria.h" |
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| #include <stdint.h> | |
| #include <stdlib.h> | |
| #include <stdio.h> | |
| #include <math.h> | |
| #include <string.h> | |
| inline uint32_t f32_to_bits(float x) | |
| { | |
| uint32_t u; memcpy(&u, &x, 4); return u; | |
| } |
Marc-B-Reynolds
/ gist:948b550fbcba3726da8bdb680b50e440
Created
April 13, 2019 22:37
factor Pi into two singles A*B
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| (* Mathematica source | |
| same method as the previous gist for double. This validates that the constants giving here are optimal: | |
| https://stackoverflow.com/questions/26692859/best-machine-optimized-polynomial-minimax-approximation-to-arctangent-on-1-1 | |
| *) | |
| (* round(Pi,48,RN) *) | |
| s = 221069929750889 | |
| (* prime factors of 's' and nearby integers *) | |
| f0 = FactorInteger[s]; |
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| (* | |
| Pi correctly rounded to 106 digits via sollya: | |
| > display=dyadic!; | |
| > round(Pi,106,RN); | |
| 63719069007931157819013617823235b-104 | |
| *) | |
| s = 63719069007931157819013617823235 | |
| (* prime factors of 's' and nearby integers *) |
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| // SEE: https://lemire.me/blog/2019/03/19/the-fastest-conventional-random-number-generator-that-can-pass-big-crush/ | |
| __uint128_t g_lehmer64_state; | |
| uint64_t lehmer64() { | |
| uint64_t r = (g_lehmer64_state >> 64); | |
| g_lehmer64_state *= 0xda942042e4dd58b5; | |
| return r; | |
| } |
Marc-B-Reynolds
/ averot.c
Last active
June 27, 2019 12:26
empirical test of average rotation angle of uniform rand rotations
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| // Public Domain under http://unlicense.org, see link for details. | |
| #include <stdint.h> | |
| #include <stdlib.h> | |
| #include <stdio.h> | |
| #include <math.h> | |
| #include <string.h> | |
| #include "xmmintrin.h" |
Marc-B-Reynolds
/ gist:80ceaf0b4724ad428d86d7c025d0d9ad
Last active
December 7, 2016 10:40
2x32-bit xorshift/weyl sequence
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| // 1 dep-chain (assuming state words in reg) to result. | |
| // DON'T USE ME UNLESS YOUR PARINOID AND | |
| // USING SOMETHING MORE EXPENSIVE (actually inferior | |
| // to some other formulations...period is only 2^32-1) | |
| // Zero is illegal for both state words. | |
| typedef struct { uint32_t s[2]; } rng_state_t; | |
| // smallcrush: passes | |
| // crush: 1 systematic failure = 72 LinearComp, r = 29 |