java.lang.OutOfMemoryError: Java heap space
at com.rwtema.denseores.WorldGenOres.retroGenSave(WorldGenOres.java:86)
at cpw.mods.fml.common.eventhandler.ASMEventHandler_390_WorldGenOres_retroGenSave_Save.invoke(.dynamic)
at cpw.mods.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:51)
at cpw.mods.fml.common.eventhandler.EventBus.post(EventBus.java:122)
at net.minecraft.world.chunk.storage.AnvilChunkLoader.func_75816_a(AnvilChunkLoader.java:126)
at net.minecraft.world.gen.ChunkProviderServer.func_73242_b(ChunkProviderServer.java:203)
at net.minecraft.world.gen.ChunkProviderServer.func_73156_b(ChunkProviderServer.java:286)
at net.minecraft.world.WorldServer.func_72835_b(WorldServer.java:164)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:609)
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:326)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:531)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:414)
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:669)

A detailed walkthrough of the error, its code path and all known details is as follows:

-- Head --
Stacktrace:
at com.rwtema.denseores.WorldGenOres.retroGenSave(WorldGenOres.java:86)
at cpw.mods.fml.common.eventhandler.ASMEventHandler_390_WorldGenOres_retroGenSave_Save.invoke(.dynamic)
at cpw.mods.fml.common.eventhandler.ASMEventHandler.invoke(ASMEventHandler.java:51)
at cpw.mods.fml.common.eventhandler.EventBus.post(EventBus.java:122)
at net.minecraft.world.chunk.storage.AnvilChunkLoader.func_75816_a(AnvilChunkLoader.java:126)
at net.minecraft.world.gen.ChunkProviderServer.func_73242_b(ChunkProviderServer.java:203)
at net.minecraft.world.gen.ChunkProviderServer.func_73156_b(ChunkProviderServer.java:286)
at net.minecraft.world.WorldServer.func_72835_b(WorldServer.java:164)

-- Affected level --
Details:
Level name: world
All players: 0 total; []
Chunk stats: ServerChunkCache: 28 Drop: 2
Level seed: 2434036188922274986
Level generator: ID 00 - default, ver 1. Features enabled: false
Level generator options:
Level spawn location: World: (0,0,0), Chunk: (at 0,0,0 in 0,0; contains blocks 0,0,0 to 15,255,15), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Level time: 0 game time, 0 day time
Level dimension: 0
Level storage version: 0x00000 - Unknown?
Level weather: Rain time: 0 (now: false), thunder time: 0 (now: false)
Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: false
Stacktrace:
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:609)
at net.minecraft.server.dedicated.DedicatedServer.func_71190_q(DedicatedServer.java:326)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:531)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:414)
at net.minecraft.server.MinecraftServer$2.run(MinecraftServer.java:669)

-- System Details --
Details:
Minecraft Version: 1.7.2
Operating System: Linux (amd64) version 2.6.32-431.11.2.el6.x86_64
Java Version: 1.7.0_55, Oracle Corporation
Java VM Version: OpenJDK 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 32064 bytes (0 MB) / 6372720640 bytes (6077 MB) up to 6372720640 bytes (6077 MB)
JVM Flags: 4 total; -Xmx6G -Xms4G -XX:MaxPermSize=512m -Xincgc
AABB Pool Size: 1596 (89376 bytes; 0 MB) allocated, 0 (0 bytes; 0 MB) used
IntCache: cache: 0, tcache: 2, allocated: 17, tallocated: 96
FML: ERROR OutOfMemoryError: Java heap space
AE2 Version: stable rv0-stable-4 for Forge 10.12.0.1024
Mantle Environment: Environment healthy.
TConstruct Environment: Environment healthy.
AE2 Integration: RotaryCraft:OFF, IC2:ON, RC:ON, BC:ON, MJ5:ON, MJ6:ON, RF:ON, RFItem:ON, MFR:OFF, DSU:ON, FZ:ON, CLApi:OFF, RB:OFF, FMP:ON
Profiler Position: N/A (disabled)
Vec3 Pool Size: 1123 (62888 bytes; 0 MB) allocated, 1109 (62104 bytes; 0 MB) used
Player Count: 0 / 20; []
Is Modded: Definitely; Server brand changed to 'fml,forge'
Type: Dedicated Server (map_server.txt)

Should be fixed in 1.4.1