41 lines
1.2 KiB
Go
41 lines
1.2 KiB
Go
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// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
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// SPDX-License-Identifier: MIT
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package grad
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import (
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"strings"
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"testing"
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)
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// Regression tests: an objective whose graph
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// never reaches x left xt.Grad() nil, and the second-order helpers
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// dereferenced it.
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// TestHessianDisconnectedObjective pins the error: an objective that
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// ignores its argument has no gradient to differentiate.
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func TestHessianDisconnectedObjective(t *testing.T) {
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x, err := FromFloat64s([]float64{1, 2}, true, 2)
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if err != nil {
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t.Fatal(err)
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}
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c, err := FromFloat64s([]float64{3}, true, 1)
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if err != nil {
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t.Fatal(err)
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}
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objective := func(*Tensor) (*Tensor, error) { return c.Mul(c) }
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if _, err := Hessian(objective, x, HessianOptions{}); err == nil {
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t.Fatal("expected an error when the objective does not depend on x")
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} else if !strings.Contains(err.Error(), "does not depend") {
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t.Fatalf("error = %v, want a disconnected-graph refusal", err)
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}
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v, err := FromFloat64s([]float64{1, 0}, true, 2)
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if err != nil {
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t.Fatal(err)
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}
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if _, err := HessianVectorProduct(objective, x, v, HessianOptions{}); err == nil {
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t.Fatal("expected an error when the objective does not depend on x")
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}
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}
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