From e6ca831f3d6924759a60b39db416a99f278de468 Mon Sep 17 00:00:00 2001
From: Andrew Kane <andrew@ankane.org>
Date: Wed, 10 Apr 2024 13:59:51 -0700
Subject: [PATCH] Store very small values as zero for halfvec

---
 src/halfvec.c                   | 33 ++-------------------------------
 test/expected/cast.out          |  8 ++++++--
 test/expected/halfvec_input.out | 16 ++++++++++------
 3 files changed, 18 insertions(+), 39 deletions(-)

diff --git a/src/halfvec.c b/src/halfvec.c
index 010c03f..4faea8f 100644
--- a/src/halfvec.c
+++ b/src/halfvec.c
@@ -53,19 +53,6 @@ HalfIsInf(half num)
 #endif
 }
 
-/*
- * Check if half is zero
- */
-static inline bool
-HalfIsZero(half num)
-{
-#ifdef FLT16_SUPPORT
-	return num == 0;
-#else
-	return (num & 0x7FFF) == 0x0000;
-#endif
-}
-
 /*
  * Get a half from a message buffer
  */
@@ -304,8 +291,6 @@ Float4ToHalf(float num)
 				(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
 				 errmsg("\"%s\" is out of range for type halfvec", buf)));
 	}
-	if (unlikely(HalfIsZero(result)) && num != 0.0)
-		float_underflow_error();
 
 	return result;
 }
@@ -401,16 +386,6 @@ halfvec_isspace(char ch)
 	return false;
 }
 
-#if PG_VERSION_NUM < 120003
-static pg_noinline void
-float_underflow_error(void)
-{
-	ereport(ERROR,
-			(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
-			 errmsg("value out of range: underflow")));
-}
-#endif
-
 /*
  * Convert textual representation to internal representation
  */
@@ -470,7 +445,7 @@ halfvec_in(PG_FUNCTION_ARGS)
 
 		x[dim] = Float4ToHalfUnchecked(val);
 
-		if ((errno == ERANGE && (isinf(val) || val == 0)) || (HalfIsInf(x[dim]) && !isinf(val)) || (HalfIsZero(x[dim]) && val != 0))
+		if ((errno == ERANGE && isinf(val)) || (HalfIsInf(x[dim]) && !isinf(val)))
 			ereport(ERROR,
 					(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
 					 errmsg("\"%s\" is out of range for type halfvec", pt)));
@@ -792,11 +767,7 @@ vector_to_halfvec(PG_FUNCTION_ARGS)
 	result = InitHalfVector(vec->dim);
 
 	for (int i = 0; i < vec->dim; i++)
-	{
-		result->x[i] = Float4ToHalfUnchecked(vec->x[i]);
-		/* TODO Better error for overflow */
-		CheckElement(result->x[i]);
-	}
+		result->x[i] = Float4ToHalf(vec->x[i]);
 
 	PG_RETURN_POINTER(result);
 }
diff --git a/test/expected/cast.out b/test/expected/cast.out
index 2286c58..0b60d3a 100644
--- a/test/expected/cast.out
+++ b/test/expected/cast.out
@@ -75,7 +75,7 @@ SELECT '[1,2,3]'::vector::halfvec(3);
 SELECT '[1,2,3]'::vector::halfvec(2);
 ERROR:  expected 2 dimensions, not 3
 SELECT '[65520]'::vector::halfvec;
-ERROR:  infinite value not allowed in halfvec
+ERROR:  "65520" is out of range for type halfvec
 SELECT '[1e-8]'::vector::halfvec;
  halfvec 
 ---------
@@ -113,7 +113,11 @@ ERROR:  expected 2 dimensions, not 3
 SELECT '{65520,-65520}'::real[]::halfvec;
 ERROR:  "65520" is out of range for type halfvec
 SELECT '{1e-8,-1e-8}'::real[]::halfvec;
-ERROR:  value out of range: underflow
+ halfvec 
+---------
+ [0,-0]
+(1 row)
+
 SELECT '[0,1.5,0,3.5,0]'::vector::sparsevec;
     sparsevec    
 -----------------
diff --git a/test/expected/halfvec_input.out b/test/expected/halfvec_input.out
index 81ce5ee..74442c9 100644
--- a/test/expected/halfvec_input.out
+++ b/test/expected/halfvec_input.out
@@ -55,17 +55,21 @@ ERROR:  "65520" is out of range for type halfvec
 LINE 1: SELECT '[65520,-65520]'::halfvec;
                ^
 SELECT '[1e-8,-1e-8]'::halfvec;
-ERROR:  "1e-8" is out of range for type halfvec
-LINE 1: SELECT '[1e-8,-1e-8]'::halfvec;
-               ^
+ halfvec 
+---------
+ [0,-0]
+(1 row)
+
 SELECT '[4e38,1]'::halfvec;
 ERROR:  "4e38" is out of range for type halfvec
 LINE 1: SELECT '[4e38,1]'::halfvec;
                ^
 SELECT '[1e-46,1]'::halfvec;
-ERROR:  "1e-46" is out of range for type halfvec
-LINE 1: SELECT '[1e-46,1]'::halfvec;
-               ^
+ halfvec 
+---------
+ [0,1]
+(1 row)
+
 SELECT '[1,2,3'::halfvec;
 ERROR:  malformed halfvec literal: "[1,2,3"
 LINE 1: SELECT '[1,2,3'::halfvec;