sign

std.elementwise.sign · Level L1

Sign of each element (−1, 0 or 1), from two comparison masks. Exact.

[x > 0] − [x < 0]

Signature

sign(x: f64[n]) → f64[n]

Structure

The function as NOVA stores it: one box per input, operation and output, and arrows that carry values. A double border marks another library function this one runs — called once, or by Scan once per element; select it to open that function.

xf64[n]0.0GreaterposLessnegSubtractyyf64[n]
  • input
  • operation
  • constant
  • call
  • output

Verification

  • Signature proven by NOVA’s shape solver, for every size.
  • Equal to the reference np.sign(x) in exact rational arithmetic, on all 40 test cases.
  • All 131 float64 results are exact: the error is zero.
  • Interpreter and NumPy backend return bit-identical results.
Accuracy in detail
correctly rounded (the float64 nearest the exact value)
100%
bit-equal to the NumPy formula in float64
100%
largest error, in units in the last place
0

Identity

Calls
—
Called by
—
sha256:c98eb1dd9defda71f2f5b2258d7d99d624cb49b94ec814d7177e7911ab2ba99e

The semantic hash of the graph. It changes when the program changes, and never when only its documentation does.

Control handle

Symbol
Ω:std.elementwise.sign · Ω:sign
Pins
sha256:d3a6d3c4b3af5024442648cb58172bbf3fc6f445f031d1107dfd9bc7b2cc6e77this graph alone
Evidence
sha256:93b43744700be980a3f27fefb092c4f1d287f3491b7be4085c863c3969bb0fd8the hash of its verification record
Needs
no capability: a pure function

Through NOVA’s control layer, the symbol launches this function only while the program still matches what it pins: a change to this graph, or to any graph it reaches, needs a migration first.