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See https://codegolf.stackexchange.com/a/203682/78112 | |
This is a description of Anders Kaseorg's solution to the code golf problem of making a program in FRACTRAN | |
that detects whether or not the Collatz sequence starting from the given number eventually reaches 1. | |
FRACTRAN programs can be thought of as being a list of chemical reactions with no catalysts (chemical | |
species that appear as both reagents and products). Given a fraction c/d, the prime factors present | |
in d (with multiplicity) are the reagent species, and the prime factors present in c (with | |
multiplicity) are the product species. Since fractions are reduced, a species is only ever either a | |
reagent or a product in a given reaction. |
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Latency Comparison Numbers (~2012) | |
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L1 cache reference 0.5 ns | |
Branch mispredict 5 ns | |
L2 cache reference 7 ns 14x L1 cache | |
Mutex lock/unlock 25 ns | |
Main memory reference 100 ns 20x L2 cache, 200x L1 cache | |
Compress 1K bytes with Zippy 3,000 ns 3 us | |
Send 1K bytes over 1 Gbps network 10,000 ns 10 us | |
Read 4K randomly from SSD* 150,000 ns 150 us ~1GB/sec SSD |