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Mish Scalar Second Derivative Tool

Evaluate the analytic second input derivative of x*tanh(softplus(x)) with reused stable forward cores.

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Description

Let p=sigmoid(x), t=tanh(softplus(x)) and a=1-t².

Mish is x*tanh(softplus(x)), combining a smooth gate with the original input. Its first and second input derivatives depend on both the gate and its derivatives. Stable scalar helper evaluation differs from differentiating a complete tensor computation or training a network.

Let p=sigmoid(x), t=tanh(softplus(x)) and a=1-t².

When to use this tool

Use Mish Scalar Second Derivative when checking the stated Mish scalar input derivative convention.

How to use the tool and how it works

  1. Enter x. Use the units and conventions below.
  2. Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
  3. Read derivative. Use the output convention below.

Let p=sigmoid(x), t=tanh(softplus(x)) and a=1-t². Return a*(2*p+x*(p*(1-p)-2*t*p²)), the second input derivative of Mish; return zero directly when a rounds to zero.1

Mish combines the input with tanh of softplus. These scalar calculus helpers do not execute a network or transfer the paper’s empirical performance claims to supplied values.2

Input fieldMeaning and unitsAccepted input
xFinite scalar input coordinate; use the mathematical scale specified above.Required. Finite number.
Output fieldInterpretationReturned shape
derivativeScalar derivative with respect to the variable and at the fixed coordinates specified above; not a tensor/model gradient.Required. Finite number.
json
{
  "input": {
    "x": 0
  },
  "output": {
    "derivative": 0.64
  }
}

Limitations and assumptions

  • This is a scalar formula with numerical saturation, not an exact symbolic tensor Hessian or a model-quality claim.
  • Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
  • Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.

Alternative or Complementary methods

Use the complete explicit function and the intended parameter, branch and numerical conventions for symbolic, tensor or model-level differentiation; assess training behavior independently.

References

  1. Calculation and input contract: activation/mish-scalar-second-derivative — tool.io

  2. Mish: A Self Regularized Non-Monotonic Activation Function — Diganta Misra

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