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lib/math: add KUnit test suite for polynomial_calc()
Add a KUnit test suite for the polynomial_calc() function, which had no in-kernel test coverage. The tests verify correct evaluation of constant, linear, quadratic, and cubic polynomials, including negative coefficients, negative input data, zero-coefficient terms. The Kconfig entry uses 'select POLYNOMIAL' rather than 'depends on POLYNOMIAL' because POLYNOMIAL is a promptless tristate that cannot be manually enabled on UML without an explicit selector. Link: https://lore.kernel.org/20260606030319.316752-1-adinata.softwareengineer@gmail.com Signed-off-by: Adi Nata <adinata.softwareengineer@gmail.com> Cc: Maxim Kaurkin <maxim.kaurkin@baikalelectronics.ru> Cc: Serge Semin <Sergey.Semin@baikalelectronics.ru> Cc: Guenter Roeck <linux@roeck-us.net> Cc: Brendan Higgins <brendan.higgins@linux.dev> Cc: David Gow <david@davidgow.net> Cc: Rae Moar <raemoar63@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Adi Nata
Andrew Morton
parent
571999ccd1
commit
a0275efa65
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@ -3504,6 +3504,23 @@ config GCD_KUNIT_TEST
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If unsure, say N
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config POLYNOMIAL_KUNIT_TEST
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tristate "Polynomial calculation (polynomial_calc) test" if !KUNIT_ALL_TESTS
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depends on KUNIT
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select POLYNOMIAL
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default KUNIT_ALL_TESTS
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help
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This option enables the KUnit test suite for the polynomial_calc()
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function, which evaluates integer polynomials using factor
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redistribution to avoid overflow.
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The test suite verifies correctness for constant, linear, and
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quadratic polynomials, negative coefficients, per-step dividers,
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divider_leftover, total_divider scaling, and a real sensor
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N-to-temperature conversion polynomial.
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If unsure, say N
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config PRIME_NUMBERS_KUNIT_TEST
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tristate "Prime number generator test" if !KUNIT_ALL_TESTS
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depends on KUNIT
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@ -4,5 +4,6 @@ obj-$(CONFIG_GCD_KUNIT_TEST) += gcd_kunit.o
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obj-$(CONFIG_INT_LOG_KUNIT_TEST) += int_log_kunit.o
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obj-$(CONFIG_INT_POW_KUNIT_TEST) += int_pow_kunit.o
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obj-$(CONFIG_INT_SQRT_KUNIT_TEST) += int_sqrt_kunit.o
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obj-$(CONFIG_POLYNOMIAL_KUNIT_TEST) += polynomial_kunit.o
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obj-$(CONFIG_PRIME_NUMBERS_KUNIT_TEST) += prime_numbers_kunit.o
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obj-$(CONFIG_RATIONAL_KUNIT_TEST) += rational_kunit.o
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270
lib/math/tests/polynomial_kunit.c
Normal file
270
lib/math/tests/polynomial_kunit.c
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@ -0,0 +1,270 @@
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// SPDX-License-Identifier: GPL-2.0-only
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#include <kunit/test.h>
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#include <linux/polynomial.h>
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struct polynomial_test_param {
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const struct polynomial *poly;
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long data;
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long expected;
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const char *name;
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};
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/* f(x) = 5 */
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static const struct polynomial poly_constant = {
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.total_divider = 1,
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.terms = {
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{0, 5, 1, 1},
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}
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};
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/* f(x) = 2x^2 + 3x + 5 */
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static const struct polynomial poly_simple = {
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.total_divider = 1,
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.terms = {
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{2, 2, 1, 1},
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{1, 3, 1, 1},
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{0, 5, 1, 1},
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}
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};
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/* f(x) = -5x + 100 */
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static const struct polynomial poly_negative_coef = {
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.total_divider = 1,
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.terms = {
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{1, -5, 1, 1},
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{0, 100, 1, 1},
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}
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};
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/* f(x) = (150x + 50) / 10 */
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static const struct polynomial poly_total_divider = {
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.total_divider = 10,
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.terms = {
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{1, 150, 1, 1},
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{0, 50, 1, 1},
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}
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};
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/*
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* f(x) = x / 2
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* divider=2 applied once per multiply: mult_frac(coef, data, 2) = coef*data/2
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*/
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static const struct polynomial poly_step_divider = {
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.total_divider = 1,
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.terms = {
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{1, 1, 2, 1},
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{0, 0, 1, 1},
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}
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};
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/*
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* f(x) = (100/500) * x^2 = 0.2 * x^2
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* Encoded as coef=100, divider=10, divider_leftover=5:
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* denom = 10^2 * 5 = 500
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*/
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static const struct polynomial poly_leftover = {
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.total_divider = 1,
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.terms = {
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{2, 100, 10, 5},
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{0, 0, 1, 1},
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}
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};
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/*
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* f(x) = 2x^3 (single high-degree term, no constant)
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* Used to exercise the power loop alone.
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*/
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static const struct polynomial poly_cubic = {
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.total_divider = 1,
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.terms = {
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{3, 2, 1, 1},
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{0, 0, 1, 1},
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}
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};
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/*
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* f(x) = 4x + 1 with a zero-coefficient quadratic term.
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* The deg-2 term contributes nothing regardless of input.
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*/
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static const struct polynomial poly_zero_coef = {
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.total_divider = 1,
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.terms = {
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{2, 0, 1, 1},
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{1, 4, 1, 1},
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{0, 1, 1, 1},
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}
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};
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/*
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* f(x) = 9 with total_divider = 0.
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* The implementation treats 0 as 1 via `total_divider ?: 1`, so the
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* result must equal the constant term unchanged.
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*/
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static const struct polynomial poly_zero_total_divider = {
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.total_divider = 0,
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.terms = {
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{0, 9, 1, 1},
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}
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};
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static const struct polynomial_test_param test_params[] = {
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{
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.poly = &poly_constant,
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.data = 0,
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.expected = 5,
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.name = "Constant polynomial at x=0",
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},
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{
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.poly = &poly_constant,
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.data = 42,
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.expected = 5,
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.name = "Constant polynomial is independent of input",
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},
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{
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.poly = &poly_simple,
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.data = 0,
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.expected = 5, /* zero input collapses all power terms */
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.name = "Zero input yields constant term only",
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},
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{
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.poly = &poly_simple,
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.data = 10,
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.expected = 235, /* 2*100 + 3*10 + 5 */
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.name = "Simple quadratic at x=10",
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},
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{
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.poly = &poly_negative_coef,
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.data = 10,
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.expected = 50, /* -5*10 + 100 */
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.name = "Negative coefficient at x=10",
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},
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{
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.poly = &poly_negative_coef,
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.data = 20,
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.expected = 0, /* -5*20 + 100 = 0 */
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.name = "Negative coefficient result is zero",
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},
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{
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.poly = &poly_total_divider,
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.data = 3,
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.expected = 50, /* (150*3 + 50) / 10 = 500/10 */
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.name = "total_divider scales the final sum",
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},
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{
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.poly = &poly_step_divider,
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.data = 100,
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.expected = 50, /* 1*100/2 */
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.name = "Per-step divider halves input",
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},
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{
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.poly = &poly_leftover,
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.data = 30,
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.expected = 180, /* 100*30^2 / (10^2 * 5) = 90000/500 */
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.name = "divider_leftover with quadratic term",
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},
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/* Boundary: unit and negative-unit input */
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{
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/*
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* data=1: each mult_frac(tmp, 1, divider) strips one factor of
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* divider from coef per degree, so coef is left-shifted right
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* until intermediate precision is exhausted.
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* 2*1 + 3*1 + 5 = 10
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*/
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.poly = &poly_simple,
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.data = 1,
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.expected = 10,
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.name = "Boundary: data=1 (unit input)",
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},
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{
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/*
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* data=-1: even degrees produce positive contributions,
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* odd degrees produce negative ones.
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* 2*(-1)^2 + 3*(-1) + 5 = 2 - 3 + 5 = 4
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*/
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.poly = &poly_simple,
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.data = -1,
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.expected = 4,
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.name = "Boundary: data=-1 (negative unit input)",
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},
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/* Boundary: negative non-trivial input */
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{
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/*
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* 2*(-3)^2 + 3*(-3) + 5 = 18 - 9 + 5 = 14
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* Verifies sign handling for negative data across all degrees.
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*/
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.poly = &poly_simple,
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.data = -3,
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.expected = 14,
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.name = "Boundary: negative data with quadratic",
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},
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/* Boundary: total_divider = 0 is treated as 1 */
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{
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.poly = &poly_zero_total_divider,
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.data = 42,
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.expected = 9,
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.name = "Boundary: total_divider=0 defaults to 1",
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},
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/* Boundary: zero-coefficient high-degree term */
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{
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/*
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* The deg-2 term has coef=0, so it contributes 0 regardless
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* of data. Result: 0 + 4*10 + 1 = 41
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*/
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.poly = &poly_zero_coef,
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.data = 10,
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.expected = 41,
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.name = "Boundary: zero-coefficient term is inert",
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},
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/* Boundary: single high-degree term, no constant */
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{
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/* 2 * 5^3 = 250; also verifies the loop terminates on deg-0 */
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.poly = &poly_cubic,
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.data = 5,
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.expected = 250,
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.name = "Boundary: single cubic term",
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},
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{
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/* 2 * (-2)^3 = -16; odd power preserves sign of negative data */
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.poly = &poly_cubic,
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.data = -2,
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.expected = -16,
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.name = "Boundary: single cubic term, negative data",
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},
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};
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static void get_desc(const struct polynomial_test_param *param, char *desc)
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{
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strscpy(desc, param->name, KUNIT_PARAM_DESC_SIZE);
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}
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KUNIT_ARRAY_PARAM(polynomial, test_params, get_desc);
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static void polynomial_calc_test(struct kunit *test)
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{
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const struct polynomial_test_param *param = test->param_value;
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KUNIT_EXPECT_EQ(test, polynomial_calc(param->poly, param->data),
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param->expected);
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}
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static struct kunit_case polynomial_test_cases[] = {
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KUNIT_CASE_PARAM(polynomial_calc_test, polynomial_gen_params),
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{}
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};
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static struct kunit_suite polynomial_test_suite = {
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.name = "math-polynomial",
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.test_cases = polynomial_test_cases,
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};
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kunit_test_suites(&polynomial_test_suite);
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MODULE_DESCRIPTION("math.polynomial_calc KUnit test suite");
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MODULE_LICENSE("GPL");
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