http://hg.viff.dk/viff/rev/b4d9b373bbab
changeset: 1084:b4d9b373bbab
user: Marcel Keller <[email protected]>
date: Tue Jan 20 10:45:50 2009 +0100
summary: Added lin_comb() to compute linear combinations of shares with less
overhead.
diffstat:
1 file changed, 28 insertions(+)
viff/passive.py | 28 ++++++++++++++++++++++++++++
diffs (38 lines):
diff -r e530dfcb40cd -r b4d9b373bbab viff/passive.py
--- a/viff/passive.py Thu Jan 15 18:30:46 2009 +0100
+++ b/viff/passive.py Tue Jan 20 10:45:50 2009 +0100
@@ -135,6 +135,34 @@
result.addCallback(lambda (a, b): a - b)
return result
+ def lin_comb(self, coefficients, shares):
+ """Linear combination of shares.
+
+ Communication cost: none. Saves the construction of unnecessary shares
+ compared to using add() and mul()."""
+
+ for coeff in coefficients:
+ assert not isinstance(coeff, Share), \
+ "Coefficients should not be shares."
+
+ assert len(coefficients) == len(shares), \
+ "Number of coefficients and shares should be equal."
+
+ field = None
+ for share in shares:
+ field = getattr(share, "field", field)
+ for i, share in enumerate(shares):
+ if not isinstance(share, Share):
+ shares[i] = Share(self, field, share)
+
+ def computation(shares, coefficients):
+ summands = [shares[i] * coefficients[i] for i in
range(len(shares))]
+ return reduce(lambda x, y: x + y, summands)
+
+ result = gather_shares(shares)
+ result.addCallback(computation, coefficients)
+ return result
+
@profile
@increment_pc
def mul(self, share_a, share_b):
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