修复plmp的一个错误

include/plmp/mpi32.h

@@ -315,6 +315,7 @@ API bool mpi_mul2i(ARGS_2_MI) noexcept { // a *= b
   }
 }
 API bool mpi_mul3(ARGS_3) noexcept { // c = a * b
+  mpi_set0(c, len);
   u32 overflow = 0;
   for (size_t i = 0; i < len; i++) {
     for (size_t j = 0; j < len - i; j++) {

test/CMakeLists.txt

@@ -22,3 +22,5 @@ add_subdirectory(misc)
 testexec(plmp plmp.c)
 testexec(plmp-cpp plmp.cpp)
 testlib(plmp-cpp util-libc-base)
+
+testexec(fib fib.c)

test/fib.c

@@ -0,0 +1,90 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#define NO_STD 0
+#include <plmp/mpi32.h>
+
+const char _plos_lut_alnum_lower[62] =
+    "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
+const char _plos_lut_alnum_upper[62] =
+    "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
+
+finline cstr tostring(u32 *_rest a, size_t len) {
+  static char buf[1024];
+  return mpi_tostr(buf, 1024, a, len, 10, true);
+}
+
+#define NBITS 1024
+#define LEN   LEN_MPI(NBITS)
+
+void fib(u32 *result, i32 x) {
+  x -= 3;
+  if (x < 0) {
+    mpi_set1(result, LEN);
+    return;
+  }
+  u32 *a  = malloc(NBITS / 8);
+  u32 *b  = malloc(NBITS / 8);
+  u32 *c  = malloc(NBITS / 8);
+  u32 *a2 = malloc(NBITS / 8);
+  u32 *b2 = malloc(NBITS / 8);
+  u32 *c2 = malloc(NBITS / 8);
+  u32 *i  = malloc(NBITS / 8);
+  u32 *j  = malloc(NBITS / 8);
+  u32 *t1 = malloc(NBITS / 8);
+  u32 *t2 = malloc(NBITS / 8);
+  u32 *t3 = malloc(NBITS / 8);
+  u32 *t4 = malloc(NBITS / 8);
+
+  mpi_set0(a, LEN);
+  mpi_set1(b, LEN);
+  mpi_set1(c, LEN);
+  mpi_set1(i, LEN);
+  mpi_set1(j, LEN);
+
+  while (x > 0) {
+    if (x & 1) {
+      mpi_mul3(t1, a, i, LEN);
+      mpi_mul3(t2, b, j, LEN);
+      mpi_mul3(t3, b, i, LEN);
+      mpi_mul3(t4, c, j, LEN);
+      mpi_add3(i, t1, t2, LEN);
+      mpi_add3(j, t3, t4, LEN);
+    }
+    mpi_mul3(a2, a, a, LEN);
+    mpi_mul3(b2, b, b, LEN);
+    mpi_mul3(c2, c, c, LEN);
+    mpi_add3(t1, a, c, LEN);
+
+    mpi_add3(a, a2, b2, LEN);
+
+    mpi_set(t2, b, LEN);
+    mpi_mul3(b, t1, t2, LEN);
+
+    mpi_add3(c, b2, c2, LEN);
+
+    x >>= 1;
+  }
+
+  mpi_add3(result, i, j, LEN);
+
+  free(a);
+  free(b);
+  free(c);
+  free(a2);
+  free(b2);
+  free(c2);
+  free(i);
+  free(j);
+  free(t1);
+  free(t2);
+  free(t3);
+  free(t4);
+}
+
+int main() {
+  u32 *result = malloc(NBITS / 8);
+  fib(result, 400);
+  printf("%s\n", tostring(result, LEN));
+  free(result);
+}