# fasta description

## Variance

Please don't optimize the cumulative-probabilities lookup (for example, by using a scaling factor) or naïve LCG arithmetic - those programs will not be accepted.

## How to implement

We ask that contributed programs not only give the correct result, but also **use the same algorithm** to calculate that result.

Each program should:

generate DNA sequences, by copying from a given sequence

generate DNA sequences, by weighted random selection from 2 alphabets

convert the expected probability of selecting each nucleotide into cumulative probabilities

match a random number against those cumulative probabilities to select each nucleotide (use linear search or binary search)

use this naïve linear congruential generator to calculate a random number each time a nucleotide needs to be selected (don't cache the random number sequence)

IM = 139968 IA = 3877 IC = 29573 Seed = 42 Random (Max) Seed = (Seed * IA + IC) modulo IM = Max * Seed / IM

**diff** program output N = 1000 with this 10KB output file to check your program output has the correct format, before you contribute your program.

Use a larger command line argument (25000000) to check program p.erformance.