Chemoinformatics in the browser: Fingerprint similarity calculation

Well there are other things that can be done in JavaScript beyond substructure search. For example, Tanimoto binary fingerprint similarity calculation needs just two short functions:

function popcount(b) {
var c, bi3b = 0xE994;
     c  = 3 & (bi3b >> ((b << 1) & 14));
     c += 3 & (bi3b >> ((b >> 2) & 14));
     c += 3 & (bi3b >> ((b >> 5) & 6));
return c;
}

function tanimoto(fp1, fp2) {
var a=0;
var b=0;
var c=0;

for (var i=fp1.length-1; i>=0; i--) {
    var block_fp1=fp1[i];
    var block_fp2=fp2[i];
    a += popcount(block_fp1);
    b += popcount(block_fp2);
    c += popcount(block_fp1 & block_fp2);
}
return c/(a+b-c);
}

The fingerprints have to be converted into JavaScript arrays of equal length containing signed numbers:

onclick="alert(tanimoto(new Array('1','-1073741825'),new Array('3','2147483647')));"

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