check all values of argminForMulVec in [1, 100000000]

include/mcl/ec.hpp

@@ -986,9 +986,13 @@ inline size_t argminForMulVec0(size_t n)
 inline size_t argminForMulVec(size_t n)
 {
 	size_t x = argminForMulVec0(n);
-	size_t v = costMulVec(n, x);
-	if (x > 1 && costMulVec(n, x-1) <= v) return x-1;
-	if (costMulVec(n,x+1) < v) return x+1;
+#if 1
+	size_t vm1 = x > 1 ? costMulVec(n, x-1) : n;
+	size_t v0 = costMulVec(n, x);
+	size_t vp1 = costMulVec(n, x+1);
+	if (vm1 <= v0) return x-1;
+	if (vp1 < v0) return x+1;
+#endif
 	return x;
 }
 

misc/mulvec_test.cpp

@@ -1,23 +1,17 @@
 #include <mcl/ec.hpp>
 #include <math.h>
 
-int f(int n, int x)
-{
-//	return int((n + pow(2, x+1) - 1)/x);
-	return int((n + (1ull<<(x+1))-2)/x);
-}
-
 void put(int n, int x)
 {
-	printf(" x=%d(%d)", x, f(n, x));
+	printf(" x=%d(%zd)", x, mcl::ec::costMulVec(n, x));
 }
 
 int getmin(int n)
 {
 	int min = 100000000;
 	int a = 0;
 	for (int x = 1; x < 30; x++) {
-		int v = f(n, x);
+		int v = mcl::ec::costMulVec(n, x);
 		if (v < min) {
 			a = x;
 			min = v;
@@ -26,25 +20,14 @@ int getmin(int n)
 	return a;
 }
 
-int getmin2(int n)
-{
-	int x = mcl::ec::argminForMulVec(n);
-	int v = f(n, x);
-	if (x > 1 && f(n, x-1) <= v) return x-1;
-	if (f(n,x+1) < v) return x+1;
-	return x;
-}
-
 void disp(int n)
 {
 	int x0 = getmin(n);
 	int x1 = mcl::ec::argminForMulVec(n);
-	int x2 = getmin2(n);
 	printf("n=%d", n);
 	put(n, x0);
 	put(n, x1);
-	put(n, x2);
-	printf(" diff=%d x0==x2=%d\n", x1-x0, x0==x2);
+	printf(" diff=%d\n", x1-x0);
 }
 
 int main()
@@ -58,4 +41,11 @@ int main()
 		disp(n);
 		disp(n*1.1);
 	}
+	puts("all search");
+	for (int i = 1; i < 100000000; i++) {
+		int x0 = getmin(i);
+		int x1 = mcl::ec::argminForMulVec(i);
+//		if (std::abs(x0-x1) > 1) printf("i=%d x0=%d x1=%d\n", i, x0, x1);
+		if (x0 != x1) printf("i=%d x0=%d x1=%d\n", i, x0, x1);
+	}
 }