Benchmark: Dataview vs Custom - Read double

Script Preparation code:

    var totalValues = 1024 * 1024;
	var valueSize = 8;
	var totalBytes = totalValues * valueSize;
	var buffer = new ArrayBuffer(totalBytes);
	// fill
	var dv = new DataView(buffer);
	for (i=0; i<totalBytes; i+=valueSize) {
	   num = Math.random()*1000;
	   if (Math.random() < 0.5) num *= -1;
	   dv.setFloat64(i,num,true);
	}
			
	
BinaryParser = function(bigEndian, allowExceptions){
    this.bigEndian = bigEndian, this.allowExceptions = allowExceptions;
};
with({p: BinaryParser.prototype}){
    p.encodeFloat = function(number, precisionBits, exponentBits){
        var bias = Math.pow(2, exponentBits - 1) - 1, minExp = -bias + 1, maxExp = bias, minUnnormExp = minExp - precisionBits,
        status = isNaN(n = parseFloat(number)) || n == -Infinity || n == +Infinity ? n : 0,
        exp = 0, len = 2 * bias + 1 + precisionBits + 3, bin = new Array(len),
        signal = (n = status !== 0 ? 0 : n) < 0, n = Math.abs(n), intPart = Math.floor(n), floatPart = n - intPart,
        i, lastBit, rounded, j, result;
        for(i = len; i; bin[--i] = 0);
        for(i = bias + 2; intPart && i; bin[--i] = intPart % 2, intPart = Math.floor(intPart / 2));
        for(i = bias + 1; floatPart > 0 && i; (bin[++i] = ((floatPart *= 2) >= 1) - 0) && --floatPart);
        for(i = -1; ++i < len && !bin[i];);
        if(bin[(lastBit = precisionBits - 1 + (i = (exp = bias + 1 - i) >= minExp && exp <= maxExp ? i + 1 : bias + 1 - (exp = minExp - 1))) + 1]){
            if(!(rounded = bin[lastBit]))
                for(j = lastBit + 2; !rounded && j < len; rounded = bin[j++]);
            for(j = lastBit + 1; rounded && --j >= 0; (bin[j] = !bin[j] - 0) && (rounded = 0));
        }
        for(i = i - 2 < 0 ? -1 : i - 3; ++i < len && !bin[i];);

        (exp = bias + 1 - i) >= minExp && exp <= maxExp ? ++i : exp < minExp &&
            (exp != bias + 1 - len && exp < minUnnormExp && this.warn("encodeFloat::float underflow"), i = bias + 1 - (exp = minExp - 1));
        (intPart || status !== 0) && (this.warn(intPart ? "encodeFloat::float overflow" : "encodeFloat::" + status),
            exp = maxExp + 1, i = bias + 2, status == -Infinity ? signal = 1 : isNaN(status) && (bin[i] = 1));
        for(n = Math.abs(exp + bias), j = exponentBits + 1, result = ""; --j; result = (n % 2) + result, n = n >>= 1);
        for(n = 0, j = 0, i = (result = (signal ? "1" : "0") + result + bin.slice(i, i + precisionBits).join("")).length, r = [];
            i; n += (1 << j) * result.charAt(--i), j == 7 && (r[r.length] = String.fromCharCode(n), n = 0), j = (j + 1) % 8);
        r[r.length] = n ? String.fromCharCode(n) : "";
        return (this.bigEndian ? r.reverse() : r).join("");
    };
    p.encodeInt = function(number, bits, signed){
        var max = Math.pow(2, bits), r = [];
        (number >= max || number < -(max >> 1)) && this.warn("encodeInt::overflow") && (number = 0);
        number < 0 && (number += max);
        for(; number; r[r.length] = String.fromCharCode(number % 256), number = Math.floor(number / 256));
        for(bits = -(-bits >> 3) - r.length; bits--; r[r.length] = "\0");
        return (this.bigEndian ? r.reverse() : r).join("");
    };
    p.decodeFloat = function(data, precisionBits, exponentBits){
        var b = ((b = new this.Buffer(this.bigEndian, data)).checkBuffer(precisionBits + exponentBits + 1), b),
            bias = Math.pow(2, exponentBits - 1) - 1, signal = b.readBits(precisionBits + exponentBits, 1),
            exponent = b.readBits(precisionBits, exponentBits), significand = 0,
            divisor = 2, curByte = b.buffer.length + (-precisionBits >> 3) - 1,
            byteValue, startBit, mask;
        do
            for(byteValue = b.buffer[ ++curByte ], startBit = precisionBits % 8 || 8, mask = 1 << startBit;
                mask >>= 1; (byteValue & mask) && (significand += 1 / divisor), divisor *= 2);
        while(precisionBits -= startBit);
        return exponent == (bias << 1) + 1 ? significand ? NaN : signal ? -Infinity : +Infinity
            : (1 + signal * -2) * (exponent || significand ? !exponent ? Math.pow(2, -bias + 1) * significand
            : Math.pow(2, exponent - bias) * (1 + significand) : 0);
    };
    p.decodeInt = function(data, bits, signed){
        var b = new this.Buffer(this.bigEndian, data), x = b.readBits(0, bits), max = Math.pow(2, bits);
        return signed && x >= max / 2 ? x - max : x;
    };
    with({p: (p.Buffer = function(bigEndian, buffer){
        this.bigEndian = bigEndian || 0, this.buffer = [], this.setBuffer(buffer);}).prototype}){
        p.readBits = function(start, length){
            //shl fix: Henri Torgemane ~1996 (compressed by Jonas Raoni)
            function shl(a, b){
                for(++b; --b; a = ((a %= 0x7fffffff + 1) & 0x40000000) == 0x40000000 ? a * 2 : (a - 0x40000000) * 2 + 0x7fffffff + 1);
                return a;
            }
            if(start < 0 || length <= 0)
                return 0;
            this.checkBuffer(start + length);
            for(var offsetLeft, offsetRight = start % 8, curByte = this.buffer.length - (start >> 3) - 1,
                lastByte = this.buffer.length + (-(start + length) >> 3), diff = curByte - lastByte,
                sum = ((this.buffer[ curByte ] >> offsetRight) & ((1 << (diff ? 8 - offsetRight : length)) - 1))
                + (diff && (offsetLeft = (start + length) % 8) ? (this.buffer[ lastByte++ ] & ((1 << offsetLeft) - 1))
                << (diff-- << 3) - offsetRight : 0); diff; sum += shl(this.buffer[ lastByte++ ], (diff-- << 3) - offsetRight)
            );
            return sum;
        };
        p.setBuffer = function(data){
           if(data instanceof Object){
                for(var l, i = l = data.length, b = this.buffer = new Array(l); i; b[l - i] = data[--i]);
                this.bigEndian && b.reverse();
            }
            if(data instanceof String){
                for(var l, i = l = data.length, b = this.buffer = new Array(l); i; b[l - i] = data.charCodeAt(--i));
                this.bigEndian && b.reverse();
            }
        };
        p.hasNeededBits = function(neededBits){
            return this.buffer.length >= -(-neededBits >> 3);
        };
        p.checkBuffer = function(neededBits){
            if(!this.hasNeededBits(neededBits))
                throw new Error("checkBuffer::missing bytes");
        };
    }
    p.warn = function(msg){
        if(this.allowExceptions)
            throw new Error(msg);
        return 1;
    };
    p.toSmall = function(data){return this.decodeInt(data, 8, true);};
    p.fromSmall = function(number){return this.encodeInt(number, 8, true);};
    p.toByte = function(data){return this.decodeInt(data, 8, false);};
    p.fromByte = function(number){return this.encodeInt(number, 8, false);};
    p.toShort = function(data){return this.decodeInt(data, 16, true);};
    p.fromShort = function(number){return this.encodeInt(number, 16, true);};
    p.toWord = function(data){return this.decodeInt(data, 16, false);};
    p.fromWord = function(number){return this.encodeInt(number, 16, false);};
    p.toInt = function(data){return this.decodeInt(data, 32, true);};
    p.fromInt = function(number){return this.encodeInt(number, 32, true);};
    p.toDWord = function(data){return this.decodeInt(data, 32, false);};
    p.fromDWord = function(number){return this.encodeInt(number, 32, false);};
    p.toFloat = function(data){return this.decodeFloat(data, 23, 8);};
    p.fromFloat = function(number){return this.encodeFloat(number, 23, 8);};
    p.toDouble = function(data){return this.decodeFloat(data, 52, 11);};
    p.fromDouble = function(number){return this.encodeFloat(number, 52, 11);};
}


doubble=new BinaryParser(false,true);
var seek=0;
var stream = new Uint8Array(buffer);

function readDouble(stream){
  var bytes=stream.subarray(seek,seek+8);
  seek=seek+8;
  return doubble.toDouble(bytes);
}

Tests:

Dataview
for (i=0; i<totalBytes; i+=valueSize) { num = dv.getFloat64(i,true); }
Custom
for (i=0; i<totalBytes; i+=valueSize) { num = readDouble(stream); }
Basecase - Just loop
for (i=0; i<totalBytes; i+=valueSize) { }

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
Dataview
Custom
Basecase - Just loop

Fastest: N/A

Slowest: N/A

Latest run results:

No previous run results

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Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

LLMs can make mistakes. Check important info.

Based on the provided code and benchmark results, I'll attempt to answer your question.

The code appears to be a JavaScript implementation of a binary parser library, specifically designed for reading and writing floating-point numbers in various formats (e.g., IEEE 754 double-precision).

The benchmark tests seem to compare the performance of three different approaches:

1. **Basecase - Just loop**: A simple loop that iterates over the data without any specific optimization or optimization technique.
2. **Dataview**: A custom implementation using a `dv.getFloat64` function, which is not shown in the code snippet.
3. **Custom**: Another custom implementation using a `readDouble` function from a `BinaryParser` class.

Based on the benchmark results:

* The **Basecase - Just loop** test has the highest number of executions per second (26.175472259521484), indicating that it is the fastest approach.
* The **Dataview** test has a much lower number of executions per second (9.262435913085938) compared to the **Basecase**, suggesting that the custom implementation using `dv.getFloat64` is less efficient than the simple loop.
* The **Custom** test has an execution count of 0, indicating that it either crashes or throws an error during the benchmarking process.

Without seeing the complete code for the `BinaryParser` class and the `dv.getFloat64` function, it's difficult to provide a specific analysis on why the custom implementations are slower than the basecase. However, it's possible that:

* The custom implementations introduce additional overhead due to the complexity of the floating-point number formats they support.
* There may be issues with memory allocation, deallocation, or other low-level details in the custom implementations that affect performance.

If you'd like me to investigate further or provide more insights, please let me know!

Related benchmarks:

Dataview vs Custom - Read double (version: 2)

Comparing performance of: Dataview vs Custom vs Basecase - Just loop

Created: 8 years ago by: Registered User

Jump to the latest result

Dataview

Custom

Basecase - Just loop

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

No previous run results

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):