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Update to the equation solver.

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This commit is contained in:
Alan Mishchenko
2025-11-10 21:03:21 -08:00
parent 677299a52f
commit 1b7912a247
1 changed files with 22 additions and 18 deletions
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40
src/misc/util/utilLinear.c
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@@ -276,7 +276,7 @@ static int verify_solution(
}
// Checks whether a particular free-variable assignment yields an integer solution.
// Optionally enforces that the first two variables differ once rounded to integers.
// Optionally enforces that the first four variables differ once rounded to integers.
static int assign_and_check_integer(
const double *rref,
int nVars,
@@ -292,7 +292,7 @@ static int assign_and_check_integer(
double *rounded,
double *out_solution,
int require_nonzero,
int require_distinct_first_two) {
int require_distinct_first_four) {
compute_solution_from_free(
rref,
nVars,
@@ -334,9 +334,13 @@ static int assign_and_check_integer(
}
}
if (require_distinct_first_two && nVars >= 2) {
if (fabs(rounded[0] - rounded[1]) < INTEGER_TOLERANCE) {
return 0;
if (require_distinct_first_four && nVars >= 4) {
for (int i = 0; i < 4; ++i) {
for (int j = i + 1; j < 4; ++j) {
if (fabs(rounded[i] - rounded[j]) < INTEGER_TOLERANCE) {
return 0;
}
}
}
}
@@ -367,7 +371,7 @@ static int search_integer_solutions(
double *rounded,
double *out_solution,
int require_nonzero,
int require_distinct_first_two,
int require_distinct_first_four,
int *explored,
int exploration_limit) {
if (*explored >= exploration_limit) {
@@ -391,7 +395,7 @@ static int search_integer_solutions(
rounded,
out_solution,
require_nonzero,
require_distinct_first_two);
require_distinct_first_four);
}
for (int i = 0; i < candidate_count; ++i) {
@@ -414,7 +418,7 @@ static int search_integer_solutions(
rounded,
out_solution,
require_nonzero,
require_distinct_first_two,
require_distinct_first_four,
explored,
exploration_limit)) {
return 1;
@@ -440,7 +444,7 @@ static int try_integer_solution(
double *rounded,
double *out_solution,
int require_nonzero,
int require_distinct_first_two) {
int require_distinct_first_four) {
if (free_count == 0) {
return 0;
}
@@ -496,7 +500,7 @@ static int try_integer_solution(
rounded,
out_solution,
require_nonzero,
require_distinct_first_two)) {
require_distinct_first_four)) {
free(free_values);
return 1;
}
@@ -519,7 +523,7 @@ static int try_integer_solution(
rounded,
out_solution,
require_nonzero,
require_distinct_first_two,
require_distinct_first_four,
&explored,
exploration_limit);
@@ -548,7 +552,7 @@ double *linear_equation_solver(double *pMatrix, int nEqus, int nVars) {
int free_count = 0;
int homogeneous_rhs = 0;
int require_nonzero_integer = 0;
int require_distinct_first_two = 0;
int require_distinct_first_four = 0;
int pivot_row_index = 0;
int rank = 0;
double max_residual = 0.0;
@@ -673,7 +677,7 @@ double *linear_equation_solver(double *pMatrix, int nEqus, int nVars) {
// Only demand integer solutions when the system is homogeneous with free variables.
require_nonzero_integer = homogeneous_rhs && free_count > 0;
// Enforce distinct first two variables whenever multiple variables remain free.
require_distinct_first_two = (free_count > 0 && nVars >= 2);
require_distinct_first_four = (free_count > 0 && nVars >= 4);
solution = (double *)malloc((size_t)nVars * sizeof(double));
workspace = (double *)malloc((size_t)nVars * sizeof(double));
@@ -711,7 +715,7 @@ double *linear_equation_solver(double *pMatrix, int nEqus, int nVars) {
rounded,
solution,
require_nonzero_integer,
require_distinct_first_two)) {
require_distinct_first_four)) {
for (int i = 0; i < free_count; ++i) {
workspace[i] = 0.0;
}
@@ -724,12 +728,12 @@ double *linear_equation_solver(double *pMatrix, int nEqus, int nVars) {
free_count,
workspace,
solution);
if (require_nonzero_integer && require_distinct_first_two) {
printf("Note: integer solution meeting non-negative and distinct-first-two constraints not found; returning floating-point solution.\n");
if (require_nonzero_integer && require_distinct_first_four) {
printf("Note: integer solution meeting non-negative and distinct-first-four constraints not found; returning floating-point solution.\n");
} else if (require_nonzero_integer) {
printf("Note: non-negative integer solution with mixed zero/positive entries not found; returning floating-point solution.\n");
} else if (require_distinct_first_two) {
printf("Note: integer solution with distinct first two variables not found; returning floating-point solution.\n");
} else if (require_distinct_first_four) {
printf("Note: integer solution with distinct first four variables not found; returning floating-point solution.\n");
} else {
printf("Note: integer solution not found; returning floating-point solution.\n");
}