From 6e6a94a6af4b53d72646324659608edf2a13c256 Mon Sep 17 00:00:00 2001
From: Anonimus <anonimus.srb2k@gmail.com>
Date: Wed, 1 Oct 2025 10:08:57 -0400
Subject: [PATCH] Add fixed-point math parity test Makes sure the more complex
 functions match regardless of bitdepth Currently (and very likely to stay)
 only FixedSqrt

---
 src/console.c  |  1 +
 src/console.h  |  1 +
 src/d_main.cpp | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 57 insertions(+)

diff --git a/src/console.c b/src/console.c
index 6acf3e205..87c3a3e1e 100644
--- a/src/console.c
+++ b/src/console.c
@@ -1654,6 +1654,7 @@ static const char *CON_LoadingStrings[LOADED_ALLDONE+1] =
 	"Init rendering daemon...", //LOADED_RINIT
 	"Init audio subsystem...", //LOADED_SINITSFXCHANNELS
 	"Cache HUD...", //LOADED_STINIT
+	"Test fixed-point arithmetic...", //LOADED_MATHINIT
 	"Init ACSVM...", //LOADED_ACSINIT
 	"Check game status...", //LOADED_DCHECKNETGAME
 	"Now starting..."
diff --git a/src/console.h b/src/console.h
index d10aeacdd..fb2f5827c 100644
--- a/src/console.h
+++ b/src/console.h
@@ -52,6 +52,7 @@ typedef enum
 	LOADED_RINIT,
 	LOADED_SINITSFXCHANNELS,
 	LOADED_STINIT,
+	LOADED_MATHINIT,
 	LOADED_ACSINIT,
 	LOADED_DCHECKNETGAME,
 	LOADED_ALLDONE = LOADED_DCHECKNETGAME,
diff --git a/src/d_main.cpp b/src/d_main.cpp
index 111490711..79a6f9d80 100644
--- a/src/d_main.cpp
+++ b/src/d_main.cpp
@@ -1814,6 +1814,61 @@ void D_SRB2Main(void)
 	ST_Init();
 	CON_SetLoadingProgress(LOADED_STINIT);
 
+	CONS_Printf("FixedSqrt of 32767 fracunits: %d; FixedSqrt64: %d\n",
+				FixedSqrt(0x7FFF0000),
+				FixedSqrt64(0x7FFF0000));
+
+	if (FixedSqrt(0x7FFF0000) == FixedSqrt64(0x7FFF0000))
+	{
+		CONS_Printf("\x83" "32767: Test OK!" "\x80" "\n");
+	}
+	else
+	{
+		CONS_Printf("\x85" "32767: Test NG!" "\x80" "\n");
+	}
+
+	CONS_Printf("FixedSqrt of 4 fracunits: %d; FixedSqrt64: %d\n",
+				FixedSqrt(0x40000),
+				FixedSqrt64(0x40000));
+
+	if (FixedSqrt(0x40000) == FixedSqrt64(0x40000))
+	{
+		CONS_Printf("\x83" "4: Test OK!" "\x80" "\n");
+	}
+	else
+	{
+		CONS_Printf("\x85" "4: Test NG!" "\x80" "\n");
+	}
+
+	// You should probably generate the weird number with RANDOM.org
+#define WEIRDNUMBER 3886284 /* 59.3 fracunits; this should approximate to around 7 */
+	CONS_Printf("FixedSqrt of 59.3 fracunits: %d; FixedSqrt64: %d\n",
+				FixedSqrt(WEIRDNUMBER),
+				FixedSqrt64(WEIRDNUMBER));
+
+	if (FixedSqrt(WEIRDNUMBER) == FixedSqrt64(WEIRDNUMBER))
+	{
+		CONS_Printf("\x83" "59.3: Test OK!" "\x80" "\n");
+	}
+	else
+	{
+		CONS_Printf("\x85" "59.3: Test NG!" "\x80" "\n");
+	}
+#undef WEIRDNUMBER
+
+	CONS_Printf("FixedSqrt64 of 65535 fracunits: %d (not possible at 32-bit scale)\n",
+				FixedSqrt64(0xFFFFFFFF));
+
+	CONS_Printf("IntSqrt of 32767: %d; IntSqrt64: %d\n",
+				IntSqrt(0x7FFF),
+				IntSqrt64(0x7FFF));
+
+	CONS_Printf("IntSqrt of 4: %d; IntSqrt64: %d\n",
+				IntSqrt(4),
+				IntSqrt64(4));
+
+	CON_SetLoadingProgress(LOADED_MATHINIT);
+
 	CONS_Printf("ACS_Init(): Init Action Code Script VM.\n");
 	ACS_Init();
 	CON_SetLoadingProgress(LOADED_ACSINIT);