1 files changed, 94 insertions, 0 deletions
diff --git a/contrib/bc/scripts/sqrt_int_guess.bc b/contrib/bc/scripts/sqrt_int_guess.bc
new file mode 100644
index 000000000000..925b7af7e103
--- /dev/null
+++ b/contrib/bc/scripts/sqrt_int_guess.bc
@@ -0,0 +1,94 @@
+#! /usr/bin/bc -l
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# Copyright (c) 2018-2024 Gavin D. Howard and contributors.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+# * Redistributions of source code must retain the above copyright notice, this
+#   list of conditions and the following disclaimer.
+#
+# * Redistributions in binary form must reproduce the above copyright notice,
+#   this list of conditions and the following disclaimer in the documentation
+#   and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+
+# Adjust this number to try ranges above different powers of 10.
+max = 0
+
+n = (1 << max)
+
+# Uncomment this to test the high part of the ranges.
+#n += (1 - (1 >> 10))
+
+n
+
+# Loop from the start number to the next power of 10.
+for (i = n; i < (n$ << 1); i += 1)
+{
+	# This is the lower limit.
+	t1 = sqrt(1/(3*i))
+
+	l = length(i$)/2
+
+	print "i: ", i, "\n"
+	#print "l: ", l, "\n"
+
+	if (l$ != l)
+	{
+		# Limit between 2.4 and 3.
+		limit = 2.7 << (l$ * 2)
+		#print "limit: ", limit, "\n"
+
+		if (i >= limit)
+		{
+			t2 = 1/(i >> (l$)) * 2
+		}
+		else
+		{
+			t2 = 1/(i >> (l$))
+		}
+	}
+	else
+	{
+		# Limit between 3.8-ish and 4.8
+		limit = 4.3 << (l$ * 2 - 1)
+		#print "limit: ", limit, "\n"
+
+		if (i >= limit)
+		{
+			t2 = 1/(i >> (l$ - 1)) * 8
+		}
+		else
+		{
+			t2 = 1/(i >> (l$ - 1)) * 4
+		}
+	}
+
+	# This is the upper limit.
+	t3 = sqrt(5/(3*i))
+
+	# This is true when the guess is in between the limits.
+	good = (t1 < t2 && t2 < t3)
+
+	print t1, " < ", t2, " < ", t3, ": ", good, "\n"
+
+	# Error if we have a problem.
+	if (!good) sqrt(-1)
+}
+
+halt