正体不明の物体、地球に接近中 月より近くを通過へ
急にこのようなニュースが目に付くようになった。
１１週間に一度あるのにいままで、ロクに報道しなかったじゃない。いままで、何故？
そして、今なぜ？
何のキャンペーン？
【ワシントン＝勝田敏彦】米航空宇宙局（ＮＡＳＡ）は１２日、正体不明の物体が米東部時間１３日午前７時４６分（日本時間同日午後９時４６分）、地球に約１２万キロ（月までの距離の約３分の１）まで最接近すると発表した。
発表によると、この物体は１０日、マサチューセッツ工科大の観測で見つかったばかり。物体の公転周期が地球とほぼ同じの１年だったため、当初はロケットの残骸（ざんがい）と考えられたが、軌道の分析から、１０～１５メートルの小惑星と考えたほうがよいという。
ＮＡＳＡによると、これぐらいの大きさの小惑星が月の距離より近いところを通過するのは１週間に１度ぐらい起きるという。
フランスは数学の国
筑波大の円周率計算の記録破る 仏技術者が通常機器で
http://sankei.jp.msn.com/science/science/100111/scn1001112106009-n1.htm
すごいね、ファブリス・ベラールさん、ＰＣが２０００ユーロでスパコンを破るんだから。もっとも、ＨＤＤが７．５ＴＢもあるのもすごい。個人で７．５ＴＢすごい時代だね。
http://bellard.org/pi/pi2700e9/announce.html
Pi Computation Record
December 31st, 2009
I am pleased to announce a new world record for the computation of the digits of Pi. The following number of digits were computed:
2242301460000 hexadecimal digits (base 16) 2699999990000 decimal digits (base 10)
The base 10 result needs about 1137 GB(1) of storage. Parts of the result are available here .
Most of the computation was carried out on a single desktop computer costing less than 2000 euros. The previous records since 1995 were done using multi-million euro supercomputers.
Computation time:
- computation of the binary digits: 103 days
- Verification of the binary digits: 13 days
- Conversion to base 10: 12 days
- Verification of the conversion: 3 days
- Total: 131 days
The previous record of about 2577 billion decimal digits was published by Daisuke Takahashi on August 17th 2009.
Formula and verification
The main computation used the Chudnovsky formula to give the binary result. Then the binary result was converted to a base 10 result.
The binary result was verified with a formula found by the author with the Bailey-Borwein-Plouffe algorithm which directly gives the n'th hexadecimal digits of Pi. With this algorithm, the last 50 hexadecimal digits of the binary result were checked. A checksum modulo a 64 bit prime number done in the last multiplication of the Chudnovsky formula evaluation ensured a negligible probability of error.
The conversion from binary to base 10 was verified with a checksum modulo a 64 bit prime number.
More technical details are available here .
Hardware
PC used during the computation:
- Core i7 CPU at 2.93 GHz
- 6 GiB (1) of RAM
- 7.5 TB of disk storage using five 1.5 TB hard disks (Seagate Barracuda 7200.11 model)
Backups were done using 2 TB hard disks (Seagate Barracuda LP model).
The verification of the binary digits used a network of 9 Desktop PCs during 34 hours. It could have been done on the same PC as the main computation by using 13 more days.
Operating System
The Linux Operating System was used with the 64 bit Red Hat Fedora 10 distribution. The 7.5 TB disk storage was managed using software RAID-0 and the ext4 filesystem. Files of up to 2.5 TB were manipulated during the computation.
Pi Software
All the software was written by the author. The most important part is an arbitrary-precision arithmetic library able to manipulate huge numbers stored on hard disks. Technical details are available here .
- (1)
- The standard SI and binary prefixes are used. For example:
- 1 GB = 10^9 bytes
- 1 TB = 10^12 bytes
- 1 GiB = 2^30 bytes (approx. 1.07 GB)
Japanってどこの国？
すごいことになってる。
- Japan is the English name for a nation comprised of a series of islands in the Pacific Ocean, east of the main Asian landmass. The roughly 128,000,000 people who live there refer to their homeland as Nippon or Nihon, and all of them are either partially or entirely crazy.
http://www.cracked.com/funny-108-japan/
訳はここ