From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Sat, 17 Jul 2021 16:06:38 +0000 (+0100)
Subject: add naive dct, remove fft variant
X-Git-Tag: xlen-bcd~273
X-Git-Url: https://git.libre-soc.org/?a=commitdiff_plain;h=0f8d9271b3a7c6b5554dbc87a759f253dda8418e;p=openpower-isa.git

add naive dct, remove fft variant
---

diff --git a/src/openpower/decoder/isa/fastdct-test.py b/src/openpower/decoder/isa/fastdct-test.py
index 60b65bd4..a525be5f 100644
--- a/src/openpower/decoder/isa/fastdct-test.py
+++ b/src/openpower/decoder/isa/fastdct-test.py
@@ -22,7 +22,7 @@
 # 
 
 import math, random, unittest
-import fastdct8, fastdctfft, fastdctlee, naivedct
+import fastdctlee, naivedct
 
 
 class FastDctTest(unittest.TestCase):
@@ -38,7 +38,6 @@ class FastDctTest(unittest.TestCase):
 			actual = fastdctlee.inverse_transform(vector)
 			self.assertListAlmostEqual(actual, expect)
 	
-	
 	def test_fast_dct_lee_invertibility(self):
 		for i in range(1, 18):
 			n = 2**i
@@ -48,55 +47,6 @@ class FastDctTest(unittest.TestCase):
 			temp = [(val * 2.0 / n) for val in temp]
 			self.assertListAlmostEqual(vector, temp)
 	
-	
-	def test_fast_dct8_vs_naive(self):
-		vector = FastDctTest.random_vector(8)
-		
-		expect = naivedct.transform(vector)
-		expect = [(val / (math.sqrt(8) if (i == 0) else 2))
-			for (i, val) in enumerate(expect)]
-		actual = fastdct8.transform(vector)
-		self.assertListAlmostEqual(actual, expect)
-		
-		expect = [(val / (math.sqrt(2) if (i == 0) else 2))
-			for (i, val) in enumerate(vector)]
-		expect = naivedct.inverse_transform(expect)
-		actual = fastdct8.inverse_transform(vector)
-		self.assertListAlmostEqual(actual, expect)
-	
-	
-	def test_fast_dct_fft_vs_naive(self):
-		prev = 0
-		for i in range(100 + 1):
-			n = int(round(1000**(i / 100)))
-			if n <= prev:
-				continue
-			prev = n
-			vector = FastDctTest.random_vector(n)
-			
-			expect = naivedct.transform(vector)
-			actual = fastdctfft.transform(vector)
-			self.assertListAlmostEqual(actual, expect)
-			
-			expect = naivedct.inverse_transform(vector)
-			actual = fastdctfft.inverse_transform(vector)
-			self.assertListAlmostEqual(actual, expect)
-	
-	
-	def test_fast_dct_fft_invertibility(self):
-		prev = 0
-		for i in range(30 + 1):
-			n = int(round(10000**(i / 30)))
-			if n <= prev:
-				continue
-			prev = n
-			vector = FastDctTest.random_vector(n)
-			temp = fastdctfft.transform(vector)
-			temp = fastdctfft.inverse_transform(temp)
-			temp = [(val * 2.0 / n) for val in temp]
-			self.assertListAlmostEqual(vector, temp)
-	
-	
 	def assertListAlmostEqual(self, actual, expect):
 		self.assertEqual(len(actual), len(expect))
 		for (x, y) in zip(actual, expect):
diff --git a/src/openpower/decoder/isa/naivedct.py b/src/openpower/decoder/isa/naivedct.py
new file mode 100644
index 00000000..efdcc567
--- /dev/null
+++ b/src/openpower/decoder/isa/naivedct.py
@@ -0,0 +1,50 @@
+# 
+# Fast discrete cosine transform algorithms (Python)
+# 
+# Copyright (c) 2020 Project Nayuki. (MIT License)
+# https://www.nayuki.io/page/fast-discrete-cosine-transform-algorithms
+# 
+# Permission is hereby granted, free of charge, to any person obtaining a copy of
+# this software and associated documentation files (the "Software"), to deal in
+# the Software without restriction, including without limitation the rights to
+# use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+# the Software, and to permit persons to whom the Software is furnished to do so,
+# subject to the following conditions:
+# - The above copyright notice and this permission notice shall be included in
+#   all copies or substantial portions of the Software.
+# - The Software is provided "as is", without warranty of any kind, express or
+#   implied, including but not limited to the warranties of merchantability,
+#   fitness for a particular purpose and noninfringement. In no event shall the
+#   authors or copyright holders be liable for any claim, damages or other
+#   liability, whether in an action of contract, tort or otherwise, arising from,
+#   out of or in connection with the Software or the use or other dealings in the
+#   Software.
+# 
+
+import math
+
+
+# DCT type II, unscaled.
+# See: https://en.wikipedia.org/wiki/Discrete_cosine_transform#DCT-II
+def transform(vector):
+	result = []
+	factor = math.pi / len(vector)
+	for i in range(len(vector)):
+		sum = 0.0
+		for (j, val) in enumerate(vector):
+			sum += val * math.cos((j + 0.5) * i * factor)
+		result.append(sum)
+	return result
+
+
+# DCT type III, unscaled.
+# See: https://en.wikipedia.org/wiki/Discrete_cosine_transform#DCT-III
+def inverse_transform(vector):
+	result = []
+	factor = math.pi / len(vector)
+	for i in range(len(vector)):
+		sum = vector[0] / 2
+		for j in range(1, len(vector)):
+			sum += vector[j] * math.cos(j * (i + 0.5) * factor)
+		result.append(sum)
+	return result