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FastSMC Python API

FastSMC includes Python bindings which can be installed using pip:

pip install asmc-asmc

Before reading further you may wish to read the FastSMC docs. In particular, these sections are directly relevant:

And, from the ASMC docs:

Examples using the Python bindings

See the notebooks directory for examples. There are two Jupyter notebooks:

  • a minimal working example, where sensible defaults for parameters are chosen automatically
  • a more detailed example that demonstrates how to customise parameters, how to convert the binary file to text format, and how to analyse the output if it is too large to fit in memory.

API

The core Python API for FastSMC consists of the following classes:

  • FastSMC
  • DecodingParams
  • BinaryDataReader

FastSMC

The main FastSMC object can be constructed minimally with an input file root, a decoding quantities file, and an output directory. Simply construct a FastSMC object and call run() to generate output in the output file root:

fast_smc = FastSMC(in_dir=input_files_root, dq_file=dq_file, out_dir=output_files_root)
fast_smc.run()

This creates a FastSMC object with sensible defaults. To fine-tune parameters you can instead create the FastSMC object with an instance of DecodingParams.

DecodingParams

Create an empty DecodingParams object:

params = DecodingParams()

The following parameters can be set:

params.decodingQuantFile = dq_file
params.inFileRoot = input_files_root
params.outFileRoot = output_files_root
params.decodingModeString = 'array'
params.usingCSFS = True
params.batchSize = 32
params.recallThreshold = 3
params.min_m = 1.5
params.hashing = True
params.FastSMC = True
params.BIN_OUT = True
params.outputIbdSegmentLength = True
params.time = 50
params.noConditionalAgeEstimates = True
params.doPerPairMAP = True
params.doPerPairPosteriorMean = True
params.hashingOnly = False

Note: the hashingOnly flag has not been extensively tested. You may also want to look into this repository for a standalone version.

Finally, you can validate that the parameters are consistent for running FastSMC:

assert params.validateParamsFastSMC()

Then, construct and run a FastSMC object using these parameters:

fast_smc = FastSMC(params)
fast_smc.run()

BinaryDataReader

If you turn on BIN_OUT in the decoding parameters, the BinaryDataReader class can read sequential lines in a file. This is useful particularly if the output is too large to process entirely in memory.

binary_data_reader = BinaryDataReader(output_files_root + '.1.1.FastSMC.bibd.gz')

while binary_data_reader.moreLinesInFile():
    line = binary_data_reader.getNextLine()

For each line, the following attributes and methods are available:

line.ind1FamId
line.ind1Id
line.ind1Hap
line.ind2FamId
line.ind2Id
line.ind2Hap
line.chromosome
line.ibdStart
line.ibdEnd
line.lengthInCentimorgans
line.ibdScore
line.postEst
line.mapEst

line.toString()