Banks and Performance
BlitzMax Forums/BlitzMax Programming/Banks and Performance
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| It is possible to increase performance using banks? I know this is a very general question, but I don't have much knowledge of banks and their common usage. If I needed to calculate "floats" but only 2 or 3 bytes of precision would this be faster than using native blitz floats? |
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| If I needed to calculate "floats" but only 2 or 3 bytes of precision would this be faster than using native blitz floats? No. Blitz's native floats use operations implemented in hardware. Literally anything you try to do to reimplement floats in software will be slower than what is already available, as it uses the fastest method available to the machine. Reducing the size of floats to a different number of bytes will slow things down even further by introducing misaligned accesses or similar problems. (Technically not quit true: you might get faster floating-point performance for some operations by using SSE or the GPU, but that's definitely getting into a separate question and can't be done in BlitzMax code.) Banks are just a wrapper around more fundamental BlitzMax data structures. They might not actually slow code down, but they definitely don't offer anything to speed it up (and they do offer ways to inadvertently slow code down, as above). They mainly exist for people coming from B3D where they were the only option for many operations. |
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| It's possible to speed up banks. By rewriting them from scratch and changing few stuff here and there. This is what I use instead of buffers (in tests it was 50-60% faster than bank in writing tons of separated bytes). It doesn't have lockbank/buffer because "data" field is already byte ptr. It doesn't do any range check, so you need to take care of staying in line. "allocated" is capacity "size" is used space (it was made for networking, size is ammount of bytes you have to send). Method Seek is for moving head (after you are done with writing, you should seek(0) to read from beggining). Function dsCreateDataBuffer:dsDataBuffer(startsize%) Local buffer:dsDataBuffer = new dsDataBuffer buffer.allocated = startsize buffer.data = MemAlloc(startsize) Return buffer EndFunction Type dsDataBuffer Method New() Seek(0) EndMethod Method Delete() MemFree(data) EndMethod Field allocated%,size% Field data:byte ptr,pos% Method Seek(pos%) Self.pos = pos EndMethod Method Clear() Seek(0) size = 0 EndMethod Method SpaceLeft%() Return allocated-size EndMethod Method GetSize%() Return size EndMethod Method GetCapacity%() Return allocated EndMethod Method Resize(size%) Local tmp:Byte ptr = memalloc(size) allocated = size MemCopy(tmp,data,size) MemFree(data) data = tmp EndMethod Method WriteByte(value:Byte) data[pos] = value pos :+ 1 size = Max(pos,size) EndMethod Method WriteShort(value:Short) (Short ptr(data+pos))[0] = value pos :+ 2 size = Max(pos,size) EndMethod Method WriteInt(value:Int) (Int ptr(data+pos))[0] = value pos :+ 4 size = Max(pos,size) EndMethod Method WriteLong(value:Long) (Long ptr(data+pos))[0] = value pos :+ 8 size = Max(pos,size) EndMethod Method WriteFloat(value:Float) (Float ptr(data+pos))[0] = value pos :+ 4 size = Max(pos,size) EndMethod Method WriteDouble(value:Double) (Double ptr(data+pos))[0] = value pos :+ 8 size = Max(pos,size) EndMethod Method WriteString(value:String) WriteShort(len(value)) For Local x% = 0 to len(value)-1 WriteShort(value[x]) next size = Max(pos,size) EndMethod Method ReadByte:Byte() pos :+ 1 Return data[pos-1] EndMethod Method ReadShort:Short() pos :+ 2 Return (Short ptr(data+pos-2))[0] EndMethod Method ReadInt:Int() pos :+ 4 Return (Int ptr(data+pos-4))[0] EndMethod Method ReadLong:Long() pos :+ 8 Return (Long ptr(data+pos-8))[0] EndMethod Method ReadFloat:Float() pos :+ 4 Return (Float ptr(data+pos-4))[0] EndMethod Method ReadDouble:Double() pos :+ 8 Return (Double ptr(data+pos-8))[0] EndMethod Method ReadString:String() Local str$,leng:Short leng = ReadShort() For Local x% = 1 to leng str :+ chr(ReadShort()) next Return str EndMethod EndType |
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| Don't use peek or poke... get the BankBuf() pointer and use pointers to read/write. |
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