Comments (4)
测试代码参数调整:
测试代码参数调整成k=9,m=18,并且模拟0, 1, 2, 5, 7, 9, 10, 14, 16列损坏,运行结果(报错)如下:
from isa-l.
I don't think this is a bug but you are pushing the limits of a Vandermonde matrix. As described in the header for gf_gen_rs_matrix for k = 9 you are not guaranteed an invertable matrix unless m <= 13. You might consider using a different encoding matrix like a Cauchy-based one the example uses. You can test this will work with:
$ ./ec_simple_example -k 9 -p 9 -e 0 -e 1 -e 2 -e 5 -e 7 -e 9 -e 10 -e 14 -e 16
ec_simple_example:
encode (m,k,p)=(18,9,9) len=8192
recover 9 fragments
check recovery of block { 0 1 2 5 7 9 10 14 16 } done all: Pass
from isa-l.
Thanks,yesterday I use Cauchy-based matrix, it does work
from isa-l.
There is a way to generate a systematic encoding matrix that is guaranteed to be invertible in any case. It works as follows:
Step 1. Generate a K by K+M Vandermonde matrix
Step 2. Generate a K by K Vandermonde matrix
Step 3. Invert the K by K Vandermonde matrix generated in step 2
Step 4. Multiply the matrix generated step 1 by the inverse Vandermonde matrix created in step 3
The matrix resulting from step 4 can serve as an encoding matrix. The first K x K rows will correspond to the identity matrix. The remaining bottom M rows can serve the purposes of encoding redundancy.
For reference, this is how the matrix is generated in other Reed-Solomon libraries, such as zfec:
https://github.com/tahoe-lafs/zfec/blob/master/zfec/fec.c#L420
from isa-l.
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from isa-l.